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S0021967320302363
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In this study for the first time stainless steel meshes coated with poly and carbon nanotubes by solgel technique were used as the adsorbent for solid phase extraction . The coated stainless steel is loaded onto a cartridge and used to isolate and extract organophosphorus pesticides from water and fruit juice samples . Effective extraction parameters such as sample volume desorption solvent and desorption solvent volume were studied and investigated . Under optimal conditions the linearity of the method was obtained in the range of 0.03 to 80ngmL
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Stainless steel meshes were coated with PEG CNT by solgel technique. The coated meshes were used as adsorbent onto a cartridge for the extraction of OPPs. The new self assembly SPE cartridge improved extraction efficiency.
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S0021967320302387
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We report on a numerical study of the thermal conductivity and temperature distribution in analytical packed bed and monolithic HPLC columns to assess the feasibility of a number of potential solutions to the viscous heating problem that would normally impede high efficiency separations when moving to extreme operating pressures . Computational fluid dynamic simulations were employed to study heat transfer on three hierarchical levels of the column mesopore level through pore level and column level . At the first level realistic values were determined for the conductivity of the porous zone
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Multilevel simulation study of viscous heating effects at pressures up to 2500bar. Effective conductivity values calculated for the materials most commonly used in LC. Halving radial temperature difference requires doubling the bed conductivity. Only structures with connected enhanced conductivity cores can achieve this. Ultra low conductivity column walls can alleviate viscous heating effects as well.
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S0021967320302399
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Phase ratio for an high performance liquid chromatography column is a parameter defined as the ratio between the volume of the stationary phase
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Evaluates the phase ratio for three C18 columns at seven temperatures between 20 C and 50 C. Shows that phase ratio in RP HPLC varies with temperature. Describes the implications of phase ratio variation with temperature on the use of vant t Hoff plots for the evaluation of enthalpy and entropy for RP HPLC separations.
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S0021967320302429
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Sensitive and specific analysis of zearalenone mycotoxin in cereals for ensuring food safety is critical and remains challenging . Herein a new gold nanoparticles @ aptamer functionalized hybrid affinity monolithic column was proposed and employed for online specific recognition of ZEN by HPLC . Characterization on the morphology BrunauerEmmettTeller surface area mechanical stability and specific performance of the obtained affinity monolith were investigated . A super high aptamer coverage density could reach 3636pmol L which is preferable to gain an effective analysis of ZEN with high specificity and a low interference of co existed substances including typical Zearalenol and Aflatoxin B
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affinity monolith was firstly used for discriminating ZEN. Ultra high aptamer coverage density of monolith column was up to 3636pmol L. Online specificity to ZEN carried out by coupling with HPLC was fulfilled. Sensitive detection was exhibited with the LOD as low as 0.05ng mL. Practical analysis of ZEN in cereals was accomplished with good results.
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S0021967320302430
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In the present study 88 structurally diverse drugs were investigated by biopartitioning micellar chromatography using Brij 35 as surfactant under different chromatographic conditions . It was found that temperature and presence of NaCl have only a minor effect in BMC retention . Correlation of BMC retention factors with octanol water partitioning required the inclusion of fractions of ionized species as additional parameters showing that there is a weaker effect of ionization in BMC environment . Compared to Immobilized Artificial Membrane Chromatography BMC retention factors cover a relatively narrow span two fold smaller than retention factors on IAM stationary phases as a result of the presence of micelles facilitating elution of lipophilic compounds and the absence of secondary attractive electrostatic interactions in the BMC environment . Similarities dissimilarities between BMC octanol water partitioning and IAM Chromatography were investigated by Linear Free Energy Relationships . BMC retention factors were used to construct relationships with cell permeability Human Oral Absorption and Plasma Protein Binding . Linear BMC models were obtained with Caco 2 cell lines and Parallel Artificial Membrane Permeability Assay . For HOA a hyperbolic model was established upon incorporation of topological polar surface area as additional parameter . A sigmoidal model was constructed for PPB and a linear one for the corresponding thermodynamic binding constant logK . In both cases inclusion of the fraction of anionic species with a positive sign was required reflecting the preference of human albumin for acidic drugs .
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Minor effect of temperature and ionic strength in BMC retention. Effect of ionization in BMC environment is rather limited. BMC retention factors cover a relatively narrow span. Potential of BMC to model essential biological processes.
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S0021967320302442
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The current study presents for the first time a combination of the gel electromembrane extraction and switchable hydrophilicity solvent based homogeneous liquid liquid microextraction methods which can be used as an efficient hyphenated extraction procedure . This coupled method which was followed by GC FID was applied for quantification of antidepressants in biological and wastewater samples . The effective parameters of both GEL EME and SHS HLLME procedures were optimized . Using an agarose gel membrane analytes were extracted from 7.0mL of the sample solution to 500 L of the aqueous acceptor solution . The maximum extraction of analytes of interest was obtained under the optimized conditions . Then the acceptor solution was transferred to the extraction cell and the SHS HLLME procedure was conducted again under the optimized conditions . Dipropylamine was selected as an extraction solvent . The introduced technique exhibited good linearities with coefficients of determinatin
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Gel electromembrane extraction was combined with liquid liquid microextraction. A switchable hydrophilicity solvent was applied in liquid liquid microextraction. High enrichment factors more recoveries and noticeable clean up were obtained. Basic drugs were determined in biological and wastewater samples by the proposed method.
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S0021967320302454
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The aim of the present study was to compare the enantioseparation performance of chiral stationary phases which were derived from chitosans of different sources and molecular weights . Therefore chitosans of shrimp and crab shells were prepared . The viscosity average molecular weights of the chitosans both prepared from shrimp and crab shells were 2.810
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The enantioseparation of shrimp crab chitosan derivatives with 4 Me was studied. The CSPs prepared from shrimp chitosan showed a little better separation ability. The CSPs derived from molecular weight MW higher chitosans had better performance. The trend between performance and MW was influenced by the substituent on CSPs.
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S0021967320302466
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In the present study a new generation of water immiscible natural deep eutectic solvents was synthesized using borneol as a hydrogen bonding acceptor and decanoic acid oleic acid and thymol as a hydrogen bonding donor in different molar ratios . These green hydrophobic solvents which are chemically stable in aqueous solutions were used as extraction solvents for isolation and pre concentration of warfarin in biological samples . In this method fine droplets of DESs were dispersed into the sample solution by using the air assisted liquid liquid micro extraction method to accelerate the cloudy emulsion system formation and increase the mass transfer of the analyte to the DES rich phase . The borneol based deep eutectic solvent is a worthy generation of the extraction solvents in the ALLME method due to low cost and less toxicity . A Plackett Burman design was utilized for screening the experimental parameters . The effective parameters were then optimized by Box Behnken design . Optimized extraction conditions were pH of sample solution of 3.9 number of aspiration dispersion cycles of 15 the volume of DES of 60 L and rate and time of centrifuge of 6000rpm and 10min respectively . Under the optimized conditions the developed NADES ALLME method exhibited a wide linear range of 5500g
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New hydrophobic deep eutectic solvents composed of natural compounds were synthesized. The prepared DESs were used as green and cost effective extraction solvent in ALLME method. The developed fast and convenient method was employed to pre concentrate and determine warfarin in complex biological samples. Response surface methodology based on box behnken design was utilized for optimization of the experiment parameters.
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S002196732030248X
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The prominent biological effects of adrenaline noradrenaline and dopamine as well as the clinical importance of their metabolites methoxy4 hydroxyphenyl glycol dihydroxyphenylglycol metanephrine normetanephrine vanillylmandelic acid homovanillic acid have forced researchers to evaluate new analytical methodologies for their isolation and preconcentration from biological samples . For this reason the three most popular extraction techniques solid phase extraction solid phase microextraction were tested . Micellar electrokinetic chromatography a mode of capillary electrophoresis with a diode array detector was applied to assess the extraction efficiency . Next the enrichment factor of each applied method was calculated in respect to standard mixtures of the analytes at the same concentration levels . The EF results of seven selected metabolites of biogenic amines from urine after sample preparation procedures based on twenty five different protocols were calculated and compared using hierarchical cluster analysis . The SPE as well as SPME procedures were proved to be the most effective approaches for the simultaneous extraction of the chosen compounds . Moreover an ionic liquid 1 ethyl 3 methylimidazolium bisimide added to methanol in SPME additionally could successfully improve the extraction efficiency . It was also confirmed that the HCA approach could be considered a supportive tool in the selection of a suitable sample preparation procedure for that group of endogenous substances .
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Comparison of three isolation techniques for. thyrosine metabolites from urine. HCA supported the selection of the most efficient extraction method. Ionic liquid used in SPME can improve the extraction efficiency for methanephrine
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S0021967320302508
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Type 1 autoimmune pancreatitis is a kind of IgG4 related disease in which higher IgG4 and total IgG levels have been found in patient serum . Due to the similar imaging features and laboratory parameters between AIP and pancreatic ductal adenocarcinoma a differential diagnosis is still challenging . Since IgG profiles can be potential bio signatures for disease we developed and validated a method which coupled on bead enzymatic protein elution process to an efficient UHPLCMS MS method to determine IgG subclass and glycosylation . A stable isotope labeled IgG was incorporated as internal standard to achieve accurate quantification . For calibration curves the correlation coefficients for total IgG and the four IgG subclasses were higher than 0.995 . Intraday
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Simple and finely optimized on bead enzymatic elution sample pretreatment. SIL IgG internal standard was incorporated for absolute quantification of endogenous IgG. Concentrations of IgG subclass and profiles of Fc glycan can be determined for pancreatic diseases. Seven IgG glycopeptides were discovered as bio signatures for differentiating AIP and PDAC.
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S0021967320302570
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New zwitterionic stationary phases are synthesized with the click and conventional bonding of tyrosine to silica gel . Infrared spectra and elemental analysis demonstrate the successful click and conventional bonding of this ZIC group on silica particles by the surface coverage including 2.36 and 0.75m
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Formation of tri azo ring in stationary phase during click reaction leads to increase the polarity of stationary phase and partitioning portion in separation mechanism. Compared to the commercial ZIC and bare silica SPs the Click Tyrosine SP provided better resolution and peak shape for narcotics. Separation of vincristine and vinblastine was performed in less time in comparison to the reversed phase chromatography.
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S0021967320302600
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The impact of eluent components added to improve separation performance in supercritical fluid chromatography was systematically and fundamentally investigated . The model system comprised basic pharmaceuticals as solutes and eluents containing an amine as additive with MeOH as the co solvent . First an analytical scale study was performed systematically investigating the impact of the additives co solvent on solute peak shapes and retentions using a design of experiments approach here the total additive concentration in the eluent ranged between 0.021 and 0.105 and the MeOH fraction in the eluent between 16 and 26 . The co solvent fraction was found to be the most efficient tool for adjusting retentions whereas the additive fraction was the prime tool for improving column efficiency and peak analytical performance . Next the impacts of the amine additives on the shapes of the so called overloaded solute elution profiles were investigated . Two principal types of preparative peak deformations appeared and were investigated in depth analyzed using computer simulation with mechanistic modeling . The first type of deformation was due to the solute eluting too close to the additive perturbation peak resulting in severe peak deformation caused by co elution . The second type of deformation was also due to additivesolute interactions but here the amine additives acted as kosmotropic agents promoting the multilayer adsorption to the stationary phase of solutes with bulkier aryl groups .
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Mechanistic modelling of separation of basic drugs accounting for additive effects. Amine additives generally sharpen solute peaks but may also deform preparative peaks. Deformed solute peaks due to co elution with additive perturbation zones. Amine additives can promote multilayer adsorption causing deformed solute peaks. Stronger multilayer tendency using primary amine additives compared higher order.
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S0021967320302612
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Herein we report three dimensional paper chromatography as a micro chromatographic platform . The method was based on applying the origami microfluidic device for separation coupled by colorimetric methods for simultaneous determination . The microfluidic device fabrication was a facile printing approach . Two azo food dyes Tartrazine and Indigo carmine were selected as a model analyte while carbonate bicarbonate buffer was used as the mobile phase . Our micro chromatographic device is associated with two big advantages including needing very small volume of mobile phase and ultrafast separation time . Under the optimal conditions the method provided acceptable linear ranges of 0 . 0gL
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A novel analytical method based on origami paper based microfluidic device as a platform for paper chromatography. Device fabrication processes is a simple single side printing and curing paper. Consumption low amount of reagents solvents and cost effective analysis. The method does not require any sample pretreatment step applying a raid analytical procedure by the green aqueous solvent
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S0021967320302624
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Consumption of ciguatoxin contaminated seafood can lead to ciguatera poisoning . The diagnosis of CP in humans is based on the clinical symptoms after eating the fish from tropical or subtropical areas because no confirmatory clinical tests are available . One of the challenges for ciguatoxin analysis is their extremely low but toxicologically relevant concentration in biological samples . We previously reported a method using acetonitrile to precipitate proteins and extract the ciguatoxins simultaneously in whole blood samples from animals for toxin quantification by N2A cell based assay . However a test method for unambiguous confirmation of exposure of marine animals or humans to ciguatoxins is still needed . In the present study we adopted the acetonitrile extraction method and added sample clean up in the sample preparation for the determination of Pacific ciguatoxins CTX1B 52
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Determination of selected Pacific ciguatoxins in blood by LC MS MS. Sample clean up methods for toxins from both groups of Pacific ciguatoxins. The MS responses of the toxins varied widely with LC mobile phase conditions. Ciguatoxin ionization profiles varied with mass spectrometers.
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S0021967320302636
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The strength of the biotin avidin interaction makes it an ideal tool for the purification of biotin labeled proteins via avidin coupled resin with high specificity and selectivity . Nevertheless this tight binding comes at an extra cost of performing the elution step under denaturing conditions . Weakening the biotin avidin interaction improves the elution conditions but only to mild or harsh denaturing buffers with the drawback of reducing the specificity and selectivity of this interaction . Here we present two chromatographic protein purification schemes that are well suited for application under native conditions thus preserving the strength of the biotin avidin interaction . In the first scheme we introduce a biotin labeled SUMO tag to each of human flap endonuclease 1 and
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Protein purification under native conditions employing the biotin avidin interaction. Single expression vector for BirA and AviTag tagged proteins. Efficient. biotinylation using BirA enzyme. An optimized release system from the biotin avidin interaction. Efficient coupling of a biotin tagged bait protein to avidin resin. Usage of bait protein coupled Agarose for affinity chromatography.
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S0021967320302648
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Ion chromatographyelectrospray tandem mass spectrometry is used to determine nine haloacetic acids bromate and dalapon in drinking water samples in U.S. EPA Method 557 . In this method all target analytes are separated and measured with good sensitivity without the need for sample preconcentration or derivatization . However the separation time is relatively long . In order to reduce the sample analysis time in EPA Method 557 a new anion exchange column has been developed to perform fast separation of the target analytes . Using this new anion exchange column nine HAAs bromate and dalapon can be resolved and separated from interfering matrix ions within 40 minutes about 33 faster than the analysis time obtained using an earlier anion exchange column reported in EPA Method 557 . The new anion exchange column has unique selectivity and high exchange capacity . Method optimization simplification and improvements in robustness are demonstrated while validating the new column suitability for the determine of HAAs bromate and dalapon according to EPA Method 557 .
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Fast and sensitive determination of haloacetic acids by IC MS MS. Direct trace level analysis of haloacetic acids. 33 faster than the current EPA method 557.
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S0021967320302673
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An optimization study of an integrated periodic counter current chromatography process in a monoclonal antibody downstream process at lab scale is presented in this paper . The optimization was based on a mechanistic model of the breakthrough curve in the protein A capture step . Productivity and resin utilization were the objective functions while yield during the loading of the capture column was set as a constraint . Different integration approaches were considered and the effect of the feed concentration yield and the protein A resin was studied . The breakthrough curve and the length of the product recovery which depended on the integration approach determined the process scheduling . Several optimal Pareto solutions were obtained . At 0.5mgmL
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This is the first to our knowledge study of the integration alternatives of multi column continuous chromatography in a downstream process. Integration approaches with higher cycle time leads to lower productivity. The use of a surge vessel after the capture allows to achieve a higher productivity. Optimal values of capture productivity and resin utilization were obtained from a model based optimization. The integrated downstream process was validated experimentally at lab scale with two KTA pure systems.
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S0021967320302831
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This paper reports a novel and rapid method for determining carboxyl groups in carbon materials by headspace gas chromatography . Taking carboxylated carbon nanotubes as an example the experiment based on GC measurement of carbon dioxide CO
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A new method for determining carboxyl groups in CNTs was proposed. Proper ultrasound can enhance the measurement efficiency. The new method is accurate simple and highly efficient. The method is significant for the quantitative study of carbon materials.
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S0021967320302843
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A new turn on fluorescent probe based on a hydrazine group placed in the meso position of the BODIPY molecule was synthesized . It was then used for detecting long chain fatty aldehydes which can be harmful to human health in edible vegetable oils . In acetonitrile the probe produced strong turn on and 100 fold fluorescence enhancement with high sensitivity and rapid response to saturated fatty aldehydes . A highly sensitive detection method for long chain fatty aldehydes was established using pre column derivation fluorescence procedure by high performance liquid chromatography . The chromatographic method established provided satisfactory precision good linearity
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A turn on fluorescent probe has been developed for the detection of fatty aldehydes. The sensor possessed high sensitivity down to 6.412.4ng mL. The probe was highly selectivity to saturated fatty aldehydes. The method has advantages of simple operation rapid reliable and micro sample.
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S0021967320302855
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The performance of columns packed with 1.7m particles for aqueous size exclusion chromatography was assessed at high pressure conditions and linked to particle and column bed integrity . Decreasing the particle size from 3.5m to 1.7m increases the resolution due to the improved mass transfer characteristics allowing to significantly speed up analysis without compromising the selectivity . A sub minute separation of intact proteins was realized on a 4.6mm i.d75mm long column packed with 1.7m SEC particles applying a flow rate of 1.8mL min corresponding to a column pressure of 530bar . Ultra high pressure operation resulted in peak deformation a shift towards earlier retention times and an alteration in selectivity . To gain insights in the mechanisms of column deterioration short 30mm long columns were operated at UHPLC conditions maximizing the pressure drop over individual particles . This resulted in the presence of fractured particles situated at the column outlet as verified by scanning electron micrographs . Mercury intrusion porosimetry and argon adsorption measurements did not reveal significant differences in intraparticle volume between particle batches sampled before and after pressure stress testing . As particles at the column outlet fracture at high pressure operation a void was formed at the column inlet . The degradation of the separation performance appeared to be the result of a decrease in interparticle pore volume .
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Column bed compression due to UHPLC operating conditions affects SEC selectivity. 1.7m particles enhances kinetic performance allowing for sub min separations. Complementary particle analysis revealed unimodal pore characteristics. High pressure operation results in bed compression which impairs chromatography.
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S0021967320302867
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We report the preparation of high performance sputtered polydimethylsiloxane coated solid phase microextraction fibers that show negligible carry over and phase bleed . This process involves sputtering silicon onto silica fibers and functionalizing the resulting porous nanostructures with ultrathin films of vapor deposited PDMS . Different thicknesses of silicon and PDMS were produced and their extraction efficiencies evaluated . The deposition of PDMS was confirmed by time of fight secondary ion mass spectrometry X ray photoelectron spectroscopy spectroscopic ellipsometry and contact angle goniometry on model planar silicon substrates . These fibers were investigated using direct immersion SPME coupled with gas chromatography mass spectrometry analysis of a series of polycyclic aromatic hydrocarbons which are carcinogenic pollutants . The 1.8m thick silicon coating with 16nm of PDMS PDMS produced the best response among the combinations tested . Conditions for the extraction of PAHs with this fiber were optimized and its extraction performance was compared to that of a commercial 7m PDMS fiber . The linearity 1110gL
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A porous silicon layer was sputtered onto a silica fiber and coated with a PDMS stationary phase for SPME. PAHs were analyzed by these fibers and commercial 7 micron PDMS fibers. About 20 times less carry over was observed with the new fibers. About 10 times less phase bleeding was observed with the new fibers. The effect of coating thickness on extraction efficiency was evaluated.
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S0021967320302879
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The ion exchange and complex forming equilibria were quantitatively described and demonstrated in order to understand major factors in the control of selectivity in the analytical separation of carboxylic acids and inorganic anions in cryptand based ion chromatography . A complex retention model has been developed for the separation on a non conventional IC column . Changes in retention are treated both theoretically and experimentally . Retention mechanism is employed on a macrocycle based ion exchange chromatographic phase to improve the selectivity for a mixture of model analytes . We introduced an alternative internal gradient method by mixed eluent . The effect of binary mixed eluent on the retention behavior and peak shape of carboxylic acids are also discussed in view of the proposed theory . It was shown that the effects of binary aqueous mobile phases held isocratically behave very similar to the step gradient mode . The internal gradient separation system has advantages over traditional step gradient mode . Twenty six anions of widely varying chemical character were investigated on the cryptand based stationary phase using different methods by LiOH NaOH and KOH eluent . The predicted vs measured retention data are in rather good agreement . High degree of linearity was obtained for inorganic anions multivalent carboxylic acids and for aromatic and haloacetic acids
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Complex retention model is described to cryptand based anion chromatography. Ion exchange and complex forming equilibria in cryptand phase with ionizable analytes were explored. Introduction of internal gradient method by mixed binary eluent. Retention behavior of carboxylic acids and inorganic anions are treated both theoretically and experimentally. The good agreement was observed between predicted and measured retention data.
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S002196732030296X
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The role of individual functional groups has been assessed with regard to surface charge and chromatographic retention . Coatings were prepared from various fragments of the chiral zwitterionic materials Chiralpak ZWIX and ZWIX . The different chromatographic ligands allowed fine tuning of the surface charge . Chiralpak ZWIX phases showed strongly negative potentials over the entire pH range . Zwitterionic congeners with quinuclidine and sulfonic acid moieties but lacking the quinolone ring in the ligand structure exhibited shifted potentials of around 5 to 20 mV depending on the surrounding residues . Capillary electrophoretic mobilitiy measurements with the chromatographic ligands and molecular dynamics simulations were carried out to offer some explanation of these surface charge differences of the distinct zwitterionic stationary phases . The new mixed mode phases were also chromatographically characterized by simple RP and HILIC tests . The results allowed their positioning within a large variety of different commercially available RP HILIC and mixed mode phases which were evaluated as well by multivariate data processing using principal component analysis . The new mixed mode phases overall exhibit reasonable hydrophilicity lipophilicity balance and enable retention of ionic compounds by additional ionic interactions through weak anion exchange strong cation exchange or both . Hence the new RP ZWIX phases can be flexible tools for selectivity tuning in RP and HILIC separations .
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New mixed mode RP WAX RP SCX and RP zwitterionic ZWIX ion exchange stationary phases. Design of chromatographic ligands by fragmentation of Chiralpak ZWIX selectors. potentials revealed finely tuned surface charge by individual increments. Molecular dynamics ruled out intramolecular ion pair formation in Chiralpak ZWIX selectors. Benchmarking study showed peculiarities compared to RP HILIC and mixed mode phases
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S0021967320302971
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In recent studies the nature and magnitude of the temperature gradients developed in ultra high pressure liquid chromatography were found to be dependent on the heat conductivity properties of the column matrices but also on the principle used for controlling the temperature over the column . Here we investigated the potential of using highly heat conductive diamond based stationary phases for reducing the temperature gradients . The stationary phases investigated were a Diamond Analytics FLARE column based on particles comprised of a graphite core surrounded by a very thin diamond shell and two silica hybrid columns a core shell silica Kromasil Eternity Shell column and a fully porous silica Kromasil Eternity XT column . Models were developed based on two dimensional heat transfer theory and mass transfer theory which were used to model the temperature profiles and the migration of an analyte band accounting for column efficiencies at different flow rates . For the silica based columns using water controlled temperature mode the temperature gradients along the column axes are suppressed whereas temperature gradients in the radial direction prevails resulting in decreased column efficiencies . Using these columns with air controlled temperature mode the radial temperature gradients are reduced whereas temperature gradients along the column prevails resulting in decreased retention times . With the Diamond FLARE column there was no loss in column efficiency using the water controlled temperature mode and the van Deemter curves are almost identical using both temperature control modes . Thus for the Diamond FLARE column in contrast to the silica based columns there are almost no losses of column efficiencies due to reduced radial temperature gradients independent on how the column temperature was controlled .
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In UHPLC significant temperature gradients are generated over the columns. In diamond columns cores of graphite vs. classical silica particles were compared. Diamond columns have 100 times larger heat conductivity than silica based columns. This eliminates radial gradients even with water based temperature control. To enhance column performance the adsorbent should have high heat conductivity.
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S0021967320302983
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A previous paper of this series of study put forward a basic model of an automated system for predicting detection limits and showed its application to a simple example of isocratic high performance liquid chromatography . This paper describes an expansion of the basic system into gradient HPLC . The most serious problem with the expansion is a long term variation in backgrounds called gradient baseline drifts which in theory can not be covered by a noise model of the original system . This paper demonstrates that the above problem can be solved with modifying a parametrization procedure of the noise model . The essential role of the system is to predict the standard deviation of measurements at low concentrations from a chromatogram without repeated measurements of real samples . Laboratory made software enables the automated assessment of the limits of detection and quantitation for each of chromatographically separated signals in a single run . Simulated background noise which consists of the stationary noise model with linear slopes is used to confirm the accuracy and reproducibility of the automated prediction . A gradient HPLC determination for cefaclor is taken as an example . The parametrization modification improves the correlation coefficient
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An automated system has been proposed to obtain detection limit DL in gradient HPLC. Quantitation limit and precision profile were also obtained by this system. Peaks on drifted baseline noise were accurately analyzed in the gradient HPLC. DL obtained by this system was essentially the same with that by S N and ISO 11843 7.
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S0021967320302995
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A new derivatization reagent N 2 oxopropanehydrazonoyl chloride was prepared and coupled with four drugs bearing primary amino secondary amino or mercapto functional groups . Glucosamine sulfate cysteine captopril and vildagliptin were used as representative reactive analytes . The prepared reagent was successfully coupled with the targeted analytes in the presence of triethylamine as hydrochloride acceptor and acetonitrile as solvent . The resulting reaction products were separated by high performance liquid chromatography and monitored simultaneously by diode array and triple quad mass spectrometry detectors . Enhanced DAD and electrospray ionization MS responses were observed for the derivatized products . Complete derivatization of VIL was achieved after heating at 653C for 4min while other analytes were derivatized instantaneously at room temperature . Both the ESI ionization suppression due to the excess reagent and matrix effect due to co eluted biogenic plasma constituents were negligible . The derivatized GLU CYS CAP and VIL showed a maximum absorption wavelength at 376 417 340 and 376nm with MS limit of quantification value of 250.0 2.0 2.5 and 3.0pg L respectively . The relative ESI MS response of UOSA54 derivatization products was within the range of 0.64.1 compared with dansylated products . The method was optimized and validated for optimal reaction product stability sensitivity linearity range precision and accuracy . The percentage recovery was exceeding 97.2 with an RSD value of less than 4.0 . The limit of quantification of targeted analytes was ranged from 80.0 to 0.7pg L .
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Preparation of new derivatization reagent for LC DAD MS analysis. The reagent reacts with NH NH. and SH functional groups. Reaction completed in acetonitrile and triethylamine. The reaction product was colored and ESI MS sensitive. Negligible ionization suppression at ESI MS and low matrix effect.
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S0021967320303009
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Capto Core 700 is a core shell chromatographic support with an adsorbing core contained within an inert shell layer designed to purify larger biomolecules and bioparticles in a flow through mode . The present study aims to characterize the structure and functional properties of this resin using bovine serum albumin and thyroglobulin as model impurity proteins . The functionalized adsorbing core and the inert shell have the same fibrous structure typical of agarose based beads . The resin average bead size is 90.7m with a range of 50130m the shell thickness is 4.18m with a range of 36m and a standard deviation of 0.55m and the pore radius obtained by inverse size exclusion chromatography is 50.41.3nm . Both proteins present highly favorable binding isotherms with maximum binding capacities of 55 and 105mg mL of total bead volume for BSA and Tg respectively . The addition of 500mM NaCl reduces the binding capacity by less than 50 showing the ability of the resin to operate at high salt conditions . For both proteins the effective pore diffusivity in the core is smaller than in the shell due to additional hindrance by bound protein in the core area . Effective pore diffusivities values in the core are 1.610
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Structural and adsorptive properties of core shell beads are characterized. Diffusion model describes transport through core and shell layer. Model predicts batch uptake and column breakthrough of model contaminants. Diffusional hindrance increases dramatically near the size exclusion limit.
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S0021967320303010
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This paper describes a procedure for the isolation of 20 organic micro pollutants among pesticides drugs recreational drugs flame retardants from river sediments . After a solid liquid extraction with a methanol water solution the supernatant was diluted with water and cleaned up by stir disc solid phase extraction . The disc was made of buckypaper a self supporting entangled assembly of carbon nanotubes which was used as a highly porous two sided sorbent membrane . In the preliminary activation step the membrane was oxidised for 2 hours with nitric acid to extend its extraction capability also to more polar compounds . All extracts were analysed by ultra high performance liquid chromatography tandem mass spectrometry . A comparative investigation with commercial Strata X Polymeric Reversed Phase SPE cartridges proved the effectiveness of the lab made device . On the average the analytes were recovered with yields around 69 and 80 while only a couple of analytes exhibited values less than 50 . The relative standard deviation was always less than 20 . Limits of detections were in the range 0.029.9ng g
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A disc SPE procedure based on the use of a buckypaper membrane has been developed. Hydrophobic emerging contaminants were cleaned up from sediment efficiently. Easiness of use and high throughput are the main advantages of the SPE device. The disc SPE device is more efficient than a conventional SPE cartridge. The buckypaper disc can be regenerated and reused up to ten times.
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S0021967320303022
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The chemical composition distribution of three single site made ethylene 1 octene copolymers was investigated through offline hyphenation of solvent gradient interaction chromatography with
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SGIC fractionation NMR proves SGIC separation by short chain branching. Elution time is related to short chain branching content by a quadratic equation. 2D LC Chemical composition related changes in molar mass distribution. Relative intensity based results differ only marginally between ELSD and IR.
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S0021967320303034
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The non parabolicity correction of the laminar flow profiles was numerically calculated for fifty nine solvents . The exact flow profiles were simulated based on sophisticated experimental literature data of dynamic viscosity and thermal conductivity and their dependency on the temperature in between cold wall temperatures of 10C up to 120C and temperature gradients up to
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Non uniformity profile in thermal filed flow fractionation. Non parabolicity correction for 59 solvents in ThFFF. Non parabolicoity correction for unipolar and aprotic solvents in ThFFF. Non parabolicity correction with one parameter in ThFFF.
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S0021967320303058
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This work presents a new triptycene based dicationic guanidinium ionic liquid as the stationary phase for gas chromatography . To our knowledge this is the first example of employing a dicationic guanidinium ionic liquid for chromatographic analyses . As a result the TPG column exhibited moderate polarity and column efficiency of 3840 plates m and 3120 plates m measured by naphthalene and 1 octanol at 120C respectively . Particularly the TPG column exhibited distinctly advantageous performance for the challenging Grob test mixture and the isomer mixture of phenols and anilines over the monocationic GIL and its counterpart with dicationic immidazolium units . Also it showed higher selectivity towards the isomers of alkanes alcohols diethylbenzenes bromotoluenes bromonitrobenzenes than the commercial DB 35MS column . Moreover the TPG column achieved improved thermal stability over the GIL column and excellent repeatability with the RSD values of 0.010.05 for run to run 0.110.24 for day to day and 2.44.1 for column to column . Its application to GCMS analysis of the essential oil of
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Triptycene based dicationic guanidinium ionic liquid. Simultaneous separation of the isomers of anilines and phenols. High selectivity towards aromatic and aliphatic isomers. Low operational temperature and improved thermal stability. Good potential for analysis of essential oils.
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S0021967320303083
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As a new kind of green solvents for potential replacement of traditional volatile organic compounds deep eutectic solvents have been attracting more and more attention in various applications . In this work three types of hydrophobic DESs were synthesized by simple mixing of trioctylmethyl ammonium chloride with decanoic acid ketoprofen and gemfibrozil respectively at different molar ratios . In order to evaluate the solvent characteristics of these DESs some of the physical properties such as melting point density viscosity and water contact angle were determined . Then these hydrophobic DESs were used for the vortex assisted liquid liquid microextraction of bisphenol type contaminants in water followed by quantitative determination of bisphenols contents with high performance liquid chromatography coupled with fluorescence detection . For this purpose four bisphenols namely 2 2 bispropane 2 2 bis butane 4 4 bisphenol and 4 4 cyclohexylidenebisphenol were selected as model contaminants . It was found that the enrichment factors of the proposed method were in the range from 97 to 112 depending on the structure of the analytes . Under optimal experimental conditions the linearity ranges of the method varied from 0.3 to 700 g L
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Several new hydrophobic deep eutectic solvents DESs were prepared. A high efficient microextraction method was developed based on hydrophobic DESs. Successfully used for the determination of bisphenols from food contacted plastics. The proposed method was simple efficient and environment friendly
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S0021967320303095
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In this study a novel and straightforward analytical methodology was proposed for the determination of cocaine and its main metabolites benzoylecgonine cocaethylene and hydroxycocaine COC
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A high throughput membrane based microextraction approach was successfully developed for the analysis of urine samples. The HFRLM 96 well plate method allowed for the preparation of up to 96 samples within 35min. The quantification of cocaine and its metabolites was possible with low sample and reagent consumption. The method developed exhibited excellent analytical performance.
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S0021967320303101
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Given the increasing need for analyzing natural or contaminating compounds in complex food matrices in a simple and automated way coupling miniaturized sample preparation techniques with chromatographic systems have become a growing field of research . In this regard given the low extraction efficiency of conventional sorbent phases the development of materials with enhanced extraction capabilities is of particular interest . Here we present several synthesized graphene based materials supported on aminopropyl silica as sorbents for the extraction of xanthines . The synthesized materials were characterized by infrared spectroscopy and scanning electron microscopy . Aminopropyl silica coated with graphene oxide and functionalized with octadecylsilane end capped showed the best performance for xanthines extraction . Hence this material was employed as an in tube solid phase microextraction device coupled online with ultra performance liquid chromatography tandem mass spectrometry and applied for the analysis of xanthines in roasted coffee samples . Extraction parameters and detection conditions were optimized . The method showed low limits of quantification 0.31.0gL
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Alkyl derivatized graphene based silica particles showed improved sorption capacity. A fully automated packed in tube SPME UPLC MS MS method was developed. Online analysis of xanthines in coffee samples was successfully implemented. Low quantification limits and high preconcentration factors were achieved.
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S0021967320303113
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This study evaluates the applicability of a method based on the direct injection of a large volume of water samples to identify and quantify 34 priority and emerging substances most of them discussed in Directive 2013 39 EU on priority substances in the field of water policy and Decision 2018 840 EU . The method directly injects 500L of filtered water sample and so does not use a pre concentration step . The method was satisfactorily validated for influent and effluent water from a drinking water treatment plant at three concentrations 1 10 and 100ngL
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The method developed is based on direct injection of 500 L of sample without pre treatment of the sample. Signal suppression due to matrix effects was observed for most of target analytes. The use of matrix matched calibration curves allowed an accurate and precise quantification of target analytes in samples. MDLs obtained with LVDI comply with the MDLs stipulated in Directive 2013 39 EU except for E1 E2 and EE2.
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S0021967320303137
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Dried blood spot sampling demonstrates multiple advantages over traditional venous blood collection in terms of quantifying biomarkers for clinical applications . The process is more convenient less invasive and requires smaller sample size . More importantly it lowers risk of infection and allows easier sample transportation and storage . In this study an automated high throughput DBS LC MS MS method was developed for quantifying endogenous biomarkers in DBS and later applied in riboflavin i.e . vitamin B
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Automated high throughput quantitative LC MS MS method in dried blood spot samples. No manual sample preparation is required. Overlapping sample extraction process and LC MS MS analysis. Only a sample of 20 L blood or other body fluid is required for each analysis. Fully validated method was applied to quantify riboflavin in 133 blood samples.
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S0021967320303149
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The Peptide RPC Column Characterisation Protocol was applied to 38 stationary phases varying in ligand chemistry base silica end capping and pore size which are suitable for the analysis of peptides . The protocol at low and intermediate pH is based on measuring retention time differences between peptides of different functionality to calculate selectivity delta values . The characterisation was designed to explore increases decreases in positive or negative charge steric effect oxidation and addition removal of aromatic moieties . The necessity of developing a characterisation protocol specifically for peptide analysis was highlighted by the fact that the small molecule databases failed to correlate with the Peptide RPC Column Characterisation Protocol . Principal Component Analysis was used to demonstrate that the protocol could be used to identify columns with similar or dissimilar chromatographic selectivity for the purpose of selectivity back up or method development columns respectively . This was validated using peptide fragments derived from the tryptic digest of bovine insulin and carbonic anhydrase . It was also demonstrated that the presence of positively charged functional groups on the stationary phase was advantageous as it yielded very different chromatographic selectivity and improved peak shape .
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38 RPC columns were characterised at low and mid pH using a peptide based protocol. Probes for hydrophobic electrostatic polar steric and aromatic interactions. No correlation with two protocols based on small molecules could be observed. Prediction of similarities and differences were validated using protein digests. Addition of positively charged functionality alters separation selectivity and improves resolution.
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S0021967320303150
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This work describes the development of a solid phase extraction method capable of detecting common fracturing fluid additives in flowback and produced water with mass spectrometry . Dissolved organic carbon was used as a bulk measurement to investigate the retentive capacity of seven sorbents and to determine a loading volume . Conductivity was used to determine rinse volume . Based on this four sorbents were selected for further investigation of their ability to recover common fluid additives . Enrichment factors were calculated for poly glycols PEG amines and their metabolites PEG carboxylates and PEG carboxylate amines poly glycols and linear alkyl ethoxylates . The sorbent HLB gave the greatest enrichment for all of these compounds with an average of 8.0for PEGs 11.9for PEG amines 4.9for PEG carboxylates and 21.6for LAEs though enrichment was highly dependent on sample composition . The effect was more pronounced for higher molecular weight compounds and enabled detection of some compounds in saltier samples . Then HLB was used to recover these additives from 1 200 and 1 1000 dilutions in groundwater illustrating the ability of solid phase extraction to detect these compounds at low levels and highlighting the utility of desalting . This method was used to identify ethoxylated amines in flowback and produced waters from across the country .
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Straightforward method to overcome matrix effects of produced water. Mass spectrometric detection enhanced with use of polymeric sorbents. Desalting and volumetric concentration both contribute to enhancement of signal. Polymeric sorbents are preferential for extraction of fracturing fluid additives. Solid phase extraction enriches common fluid additives in raw and dilute samples
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S0021967320303162
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A two membrane electrodialytic carbonate eluent generator for ion chromatography is described . It is in a sandwich like configuration in which the central eluent channel is spatially isolated from two outer regenerant channels by stacked cation exchange membranes and anion exchange membranes . A platinum screen electrode is placed in each of two outer regenerant channels . The electrode at the CEMs side is set as an anode with respect to the electrode at the AEMs side being cathode . Potassium carbonate and or bicarbonate solution is pumped into the regenerant channel as feed solution . The electromigration of carbonate and or bicarbonate and potassium from feed solution respectively through AEMs and CEMs will form a gas free eluent . With this configuration ion transport behavior through AEMs was explored . The device demonstrated good reproducibility as indicated by the relative standard deviation of retention time of less than 0.08 .
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A two membrane electrodialytic carbonate generator has been described. Ion transport behavior in such generator has been explored. Different composition of eluent generated relative to manually prepared.
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S0021967320303174
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The main focus of the present research was the on line coupling of two separation techniques namely liquid chromatography and gas chromatography . For such an analytical combination a dedicated interface is required to remove solvent from the sample leaving the latter in a sharp band at the head of the GC column . Considering such an objective a lab developed LC GC interface is herein presented based on the use of a six port two position valve and a programmed temperature vaporizing injector . The PTV injector was derived from a commercial split splitless injector body heated using a resistance heating wire and enabled a satisfactory recovery of low boiling compounds C
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An improved lab developed interface for LC GC coupling was developed. The modified PTV injector allows a better recovery of low boiling compounds. The method was characterized by satisfactory figures of merit for MOSH.
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S0021967320303216
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The aim of the present investigation was application of hydrophilic interaction liquid chromatography as an alternative chromatographic approach for the study of antisense oligonucleotides . The influence of several mobile phases differing with the salt type their concentration and pH value on the retention and the separation of antisense oligonucleotides has been examined for this purpose . Four different stationary phases were also applied including unmodified silica silica modified with the use of sulfobetaine groups polyhydroxy and aminopropyl groups . Such wide range of tested conditions has been useful in better understanding of the retention mechanism of tested compounds . The results obtained during this investigation indicated that greater retention greater peaks symmetry as well as more effective separation of oligonucleotides were obtained for the zwitterionic stationary phase . Moreover the optimization of tandem mass spectrometry parameters with the use of Central Composite Design was performed and different mobile phases were tested to choose that one which provided the greatest antisense oligonucleotides peak areas in Multiple Reaction Monitoring mode and consequently the greatest possible sensitivity . Hydrophilic interaction liquid chromatography was compared with the ion pair chromatography commonly used in the analysis of oligonucleotides . Both techniques were compared in terms of selectivity of separation as well as the sensitivity of their determination . Obtained results proved that ion pair chromatography provided better results in terms of separation efficiency and peak areas in Multiple Reaction Monitoring for tested conditions . However these results do not preclude application of hydrophilic interaction liquid chromatography as an alternative chromatographic approach for the oligonucleotides analysis especially when a mobile phase without ion pair reagents is required .
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Salt type its concentration and pH values had an influence on the retention of ASOs for both silica and zwitterionic stationary phases in HILIC mode. Zwitterionic stationary phase provided greater ASOs retention factors greater peaks symmetry as well as more effective MOE separation. Salt type its concentration and pH had a great impact on the ASOs MRM peak areas in HILIC mode. Comparison of IP RP HPLC and HILIC mode coupled with tandem mass spectrometry regarding the MS sensitivity has shown that greater ASO MRM peak areas were obtained for IP RP HPLC. HILIC coupled with MS MS may be alternatively used for ASOs separation and determination.
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S002196732030323X
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With the advent of highly selective analysis techniques and lower limits of detection requirements extraction efficiency is arguably the most important property of modern sample preparation techniques . In this study the extraction efficiency of Ice Concentration Linked with Extractive Stirrer was compared to Stir Bar Sorptive Extraction and Solid Phase Microextraction . A direct comparison of these sample preparation techniques was carried out with analysis via both Liquid Chromatography Tandem Mass Spectrometry and Thermal Desorption Gas Chromatography Mass Spectrometry . ICECLES produced 2x and 7x greater TD GCMS signals than SBSE and SPME respectively . When comparing extraction techniques for a suite of 60 pesticides in drinking water 32 25 and 13 pesticides were detected via LCMS MS at 0.1ng mL by ICECLES SBSE and SPME respectively . Overall ICECLES consistently produced better extraction efficiencies than the other extraction techniques evaluated .
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ICECLES was directly compared to SBSE and SPME for the analysis of atrazine via HPLCMS MS. ICECLES was directly compared to SBSE and SPME for the analysis of several analytes via TD GCMS. ICECLES allowed HPLCMS MS detection of 32 pesticides at 0.1ng mL. ICECLES demonstrated excellent extraction efficiencies for multiple compounds over a wide range of log Kow values from water. ICECLES allows for detection via TD GCMS and HPLCMS MS.
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S0021967320303253
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The coexistence of the anilinopyrimidine fungicides pyrimethanil and cyprodinil and suspected metabolites in wine samples was investigated by liquid chromatography with tandem mass spectrometry based on triple quadrupole and quadrupole time of flight MS instruments . For the first time quantitative data obtained after solid phase extraction of wine samples have demonstrated the systematic presence of 4 hydroxyanilino derivatives of PYR and CYP in wines containing residues of parent fungicides at concentrations from 0.2 to 58ngmL
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4 hydroxyanilino metabolites of cyprodinil and pyrimethanil quantified in wine. Higher levels of 4 hydroxyanilino pyrimethanil than active fungicide in red wine. Additional hydroxylated metabolites identified from their accurate MS spectra. Hydroxylated metabolites coexist as free and glycosylated forms.
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S0021967320303423
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A method to thermodynamically model the alkane isovolatility curves of a comprehensive two dimensional gas chromatography separation is presented . This method omits all instrument modifications additional chromatogram collection or method alterations which typical isovolatility curve generation requires . Provided that the thermodynamic indices of reference alkanes are available chromatographers only need to specify the GCGC method parameters of their separation to output the isovolatility curves . The curves can then be used alongside reference retention indices to generate two dimensional retention times for each analyte . Agreement between the modeled and experimental retention times provides a secondary mechanism for compound identification supporting the results of a mass spectral search . The technique was used to model the retention times of a GCGC separation of aromatic hydrocarbons achieving an average first dimension retention time modeling error of 11s and an average second dimension retention time modeling error of 0.09s . Retention indices modeled retention times provide a simpler analyte identification procedure compared to conventional two dimensional retention indices matching .
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A method to thermodynamically model GCGC isovolatility curves presented. Isovolatility curves are used for 2D retention indices analyte identification. Identification accuracy is evaluated using a GCGC aromatic hydrocarbon separation. Identification accuracy is compared across retention indices collected at various temperatures.
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S0021967320303435
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Fixed bed adsorption is widely used for separations and purifications of active components in medicine and for wastewater treatment . At present fixed bed adsorption breakthrough curve is generally obtained by manual sampling and off line detection . In this study we proposed a method for on line monitoring of fixed bed adsorption process using a self assembled fiber optic sensing system . The adsorption of 2 4 dichlorophenoxyacetic acid on the fixed bed packed with molecularly imprinted polymers and non imprinted polymers were studied . The reproducibility and precision of the system was investigated . The relative standard deviation of the system was less than 1.54 which indicates that the system has a good reproducibility . The effects of initial concentration flow rate adsorbent mass and particle size on the breakthrough curves were investigated . Through screening it was found that adsorption kinetics of the polymer materials fit to Thomas and Yoon Nelson models . The MIPs showed high binding capacity good selectivity fast adsorption rate indicating a great potential for the treatment of 2 4 D contaminated water . Moreover this study has identified that the detection method has the advantages of being on line realtime simple and accurate . The on line method can facilitate the study of fixed bed adsorption processes and accelerate the understanding of adsorption kinetics .
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On line realtime measurement of fixed bed adsorption process was proposed based on fiber optic sensing. The method could provide breakthrough curves with whole data. High accuracy and reproducibility with less time and labor cost were attained owing to on line and automatic process. Simple instrumentation with easy operation greatly accelerated analysis process and satisfied wider practical needs. The imprinted polymers demonstrated great potential application in the treatment of 2 4 D wastewater.
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S0021967320303484
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To obtain consistent chromatographic behavior it is important to develop resin packing methods in accordance with the characteristics of each resin . Resins particularly those with a significant level of compressibility require proper knowledge of the packing methodology to ensure scalable performance . The study demonstrates the applicability of pressure flow modeling based on the BlakeKozeny equation for cellulose based resins using the MEP HyperCel resin as a case study . This approach enabled the understanding of the appropriate bed compressibility and the determination of the minimum column diameter that can predict bed integrity during commercial manufacturing scale operation . Studies suggested that scale dependent wall effects become negligible for column diameters exceeding 20cm . Pressure flow modeling produced a minimum compression recommendation of 0.206 for the MEP HyperCel resin . Columns with diameters up to 80cm packed with this bed compression yielded incompressible beds with pressure flow curves consistent with model predictions . Model parameter values were then varied to demonstrate how changing operating conditions influence model predictions . This analysis supported the successful troubleshooting of unexpected high pressures at the commercial manufacturing scale using MEP HyperCel resin further supporting the applicability of this approach .
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Consistent and scalable chromatographic behavior requires well packed columns. Pressure flow modeling based on the BlakeKozeny equation informs packing methods. This modeling also allows troubleshooting of unexpected chromatographic behavior. A case study demonstrates this modeling and troubleshooting for MEP HyperCel resin.
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S0021967320303502
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Next to furan other alkylfurans such as 2 and 3 methylfuran 2 ethylfuran 2 5 dimethylfuran and 2 pentylfuran have been found concurrently in thermal processed food and fruit juices . To ensure an accurate quantification of these compounds a method based on isotope dilution using all six respective internal standards and gas chromatography coupled to mass spectrometry was developed . Two injection techniques static head space and solid phase micro extraction were tested and compared for their performance . Validation was based on a single laboratory validation under repeatability condition . Good data for both techniques in baby food and cereals were obtained . Furthermore validation was conducted successfully on fruit juices and infant formula using SPME injection and on coffee using HS injection . LOQ for all matrices was established at 5 g kg and 200 g kg in coffee samples which corresponds to the lowest fortification level . Recovery was between 80 and 110 and repeatability obtained below 16 at 50 g kg except few slight outliers .
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Quantitative detection of Furan and 5 alkylfurans using GC MS. Use of respective internal standards for each compound obligatory. HS and SPME injection systems give comparable results. Successful validation of baby food and cereals using both techniques. Successful validation of coffee using HS fruit juice and infant formula using SPME
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S0021967320303514
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The characterisation of the energetic properties of liquid crystals i.e . esters with elongated molecules has been performed . The changes of the free energies of adsorption and absorption
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IGC technique is employed to explore of the variation of the Gibbs free energy. and free energy. of adsorption and dissolution at the temperatures characteristic for crystalline smectic and nematic phases. The physicochemical properties of liquid crystalline stationary phases and the widening of the Dorris Gray concept on the liquid crystalline phases is proposed. The interpretation based on a precise van der Waals component of the surface free energy. is presented in a more detailed form.
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S0021967320303526
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In this work a new method for the determination of 5 hydroxymethylfurfural in cereal and insect bars has been developed and validated . The method consisted of a solid liquid extraction followed by a solid phase extraction employing functionalized mesostructured silica as sorbent and prior to high performance liquid chromatography coupled to mass spectrometry analysis . Mesostructured silica with a large pore functionalized with aminopropyl groups SBA 15 LP NH
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Development and validation of a new method to determine hydroxymethylfurfural. Functionalized silica based sorbent was applied in solid phase extraction. Analysis by high performance liquid chromatography mass spectrometry. High concentration of hydroxymethylfurfural was found in cereal and insect bars.
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S0021967320303538
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To understand the overall processes behind the decomposition of state of the art organic liquid electrolytes in lithium ion batteries it is necessary to investigate and quantify the permanent gases and light hydrocarbons evolving during electrolyte decomposition . In this work a convenient way of sampling gas from pouch cells without any previous preparation of the cell as well as a comprehensive gas chromatographic investigation of the gas phase is shown . A barrier discharge ionization detector was utilized for gas quantification and a multi component gas standard in combination with a gas mixing device was implemented to prepare calibration standards for validation . Therefore sensitivity linearity and reproducibility as well as the limits of detection and limits of quantification were determined .
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A barrier ionization discharge detector was utilized for gas quantification. Comparison to a thermal conductivity detector. The BID exceeded the TCD detector in figures of merit. Gas from bloated pouch cells was analysed.
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S002196732030354X
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Since metabolism is implicated in the carcinogenesis of toxicants an efficient extraction method together with an analytical method is warranted to quantify tissue burdens of a carcinogen and or its metabolites . Therefore the aim of this study was to validate a pressurized liquid extraction method for measuring metabolites of benzopyrene P a food borne carcinogen from tissue samples . The sample extraction was performed separately by PLE and liquidliquid extraction . PLE followed by high performance liquid chromatography coupled to online fluorescence detector was used to quantify separated analytes and by ultra high performance liquid chromatography coupled to atmospheric pressure chemical ionization tandem mass spectrometry were used for confirmation purposes . The UHPLC MS MS was set up in the atmospheric pressure chemical ionization positive interface with selective reaction monitoring . The analytical performance characteristics of the PLE technique was assessed at different temperatures pressure number of cycles and solvent types . A methanol chloroform water mixture yielded greater recoveries at an extraction temperature range of 6080C pressure of 10MPa and an extraction time of 10min . The PLE method was validated by the analysis of spiked tissue samples and measuring recoveries and limits of quantitation for the analytes of interest using HPLC FLD equipment . The optimized PLE HPLC FLD method was used to quantify the concentrations of BP metabolites in liver samples obtained from a colon cancer animal model . Overall PLE performed better in terms of extraction efficiency recovery of BP metabolites and shortened sample preparation time when compared with the classic LLE method .
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Efficiency of extraction is important to measure body burden of carcinogens. Liquidliquid extraction LLE do not extract PAH metabolites from tissues exhaustively. Pressurized liquid extraction PLE is a more efficient extraction technique than LLE. An PLE method was validated for quantitation of benzo a pyrene metabolites from tissues.
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S0021967320303551
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The aim of this study was to determine the impact of the origin and the manufacturing processes of the chiral stationary phases on their chromatographic behaviors . Hence four chiral stationary phases based on immobilized
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Polysaccharide with the same chiral selector columns from different manufacturers. Twenty pharmaceutical compounds and nine in house compounds chosen as probes. Study of the chromatographic parameters on each column. Evaluation of the loading capacity of each column. Ranking of the performances of the four columns investigated.
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S0021967320303563
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Gas chromatographic columns based on ionic liquids are very promising since the selectivity of these columns can be tuned by both the cation and the anion chemical nature . In this paper efficiencies of capillary columns based on four phosphonium ionic liquids were studied . The performance of seven columns containing the cation trihexylphosphonium and the anions bromide chloride and bisimide was evaluated by measuring the solute band broadening as a function of gas velocities at three temperatures . Hence classical height equivalent to a theoretical plate against gas velocity plots corresponding to those columns were generated and the data were fitted to the Golay Guiochon equation with the aim of seeking the optimum conditions to be operated each of them . Band broadening at practical gas velocities is mainly due to poor mass transfer properties of solutes in the liquid phases which limits the achieved efficiencies . These H u plots proved to be necessary to characterize the column quality at a given temperature to interpret the band broadening phenomena and thus to establish the lower temperature limits and the expected plate counts at that temperature .
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Solute band broadening in phosphonium based ionic liquid GC columns were measured. Resistance to mass transfer into the viscous liquid film is the main contribution. Column efficiency at high velocities are almost independent of the used carrier gas. The column radius has minor importance for improving efficiency at optimum velocity. The lower temperature limits for using these columns should be redefined. Silica pretreatment by burning Carbowax 20M is preferred over precipitation of salt
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S0021967320303575
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We present high resolution fast cost effective and sensitive Capillary zone electrophoresis methods for determination of enantiomeric compounds of Kynurenine pathway i.e . D L Kynurenine in human serum and urine samples by cationic CD and its synergistic dual chiral selector system with CD in 50 mM borax borate buffer as BGE . Acid mediated stacking enrichment by HCl delivered 15 nM limit of detection and 50 nM limit of quantification . The methods gave advantages of linearity in the concentration range of 50 nM 1000 nM reproducibility selectivity against interfering amino acids and remarkable recoveries . SD CSs delivered resolution of D L KYN twice that of individual chiral selectors under similar conditions . The binding constants
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Determination of nanomolar D L Kynurenine in human serum and urine with CE UV detector and acid mediated stacking. Mechanism of two types of CDs synergistic effect for D L Kynurenine high resolution separation based on molecular docking and molecular mechanics. High resolution and highly sensitive fast analytical method development for D L Kynurenine determination.
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S0021967320303587
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This work describes the development of capacity orthogonal chromatography a new technique for simultaneously determining the loading capacity and orthogonality during the construction of two dimensional separations . Three steps were required for the construction of a COC based on the correlation between the selectivity factor
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New method of 2D separation was developed. The method could optimize orthogonality and loading capacity simultaneously. Theoretical fundamental and practical terms of the new method were discussed. The method was used to purity 228 mg corilagin from pomegranate flower extracts.
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S0021967320303599
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The interactions and dynamic behavior of a select set of polar probe solutes have been investigated on three hydrophilic and polar commercial stationary phases using saturation transfer difference
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Stationary phase ligands have a strong contribution to the selectivity in HILIC. The retention mechanism has a significant contribution from oriented interactions. STD NMR can be a powerful tool to investigate interactions in chromatography.
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S0021967320303605
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A carbazolic conjugated microporous polymer was successfully synthesized through Scholl reaction of carbazole with 1 3 5 triphenylbenzene . The CZ CMP was characterized by FT IR spectrum X ray diffraction nitrogen sorption isotherms and scanning electron microscopy . The characterization results showed that the CZ CMP had a spherical structure with high surface area and good microporosity . Its adsorption performance was investigated by applying it as an adsorbent for the solid phase extraction of phenyl urea herbicides from tea drinks samples prior to high performance liquid chromatographic detection . The CZ CMP displayed high extraction efficiency for the PUHs and the primary factors affecting the SPE efficiency including the type and volume of the eluent sample solution pH sample loading rate and sample volume were optimized . Under the optimized conditions a good linear response for the analytes was observed in the range of 0.1080.0ng mL
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A porous organic polymer was synthesized for the first time by scholl reaction. It is an effective SPE adsorbent for the extraction of phenyl urea herbicides. It had a good stability and reusability.
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S0021967320303617
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A novel and simple derivatization method using a series of amide acetals as derivatization reagents along with gas chromatography tandem mass spectrometry analysis were developed and validated for simultaneous determination of 9 perfluoroalkyl carboxylic acids in this study . The structures and fragmentation pathway of PFCAs derivatives were deduced and verified . The derivatization method developed in this study improved the sensitivity of the detection of PFCAs by GC . The applicability of 6 amide acetals for the derivatization of PFCAs was demonstrated . Derivatization conditions for 9 PFCAs were optimized with addition of 20 L of derivatization reagent and reaction at 35 C for 30min . 9 PFCAs derivatives were confirmed to be stable over 15 days . The instrument detection limits were lower than 0.01 pg L. The intra and inter day precisions were below 4.06 and 5.48 respectively . To demonstrate the utility of the derivatization method the level of PFCAs in the marine products were detected . The alkaline digestion followed by solid phase extraction cleanup method was used for pretreatment . The method detection limits ranged from 0.04 to 0.10ng g and the spiked recoveries ranged between 54.72 and 107.29 with relative standard deviation of 1.53 11.89 . Five PFCAs were detected in the range of 0.66 to 499.03ng g dry weight .
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The first application of a series of amide acetals in derivatization reaction employed for 9 PFCAs. The structures and fragmentation pathway of PFCAs derivatives were deduced and verified. The new derivatization method combined with GCMS MS has high sensitivity and accuracy. The application of this method was validated by detecting PFCAs in marine products.
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S0021967320303629
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This work reports procedures for the immobilization of vinyl ligands on silica particles by UV initiated thiol ene radical addition reaction .
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Immobilization of chromatographic ligands by thiol ene click reaction. UV irradiation of photoinitiator generates radicals and initiates reaction. Direct photoclick immobilization of chiral quinine carbamate on thiol silica. Solventless photoclick bonding of selector via polythiol film on vinyl silica. Systematic study of reaction conditions to optimize surface coverage.
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S0021967320303630
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The isomerization of amino acids in peptides and proteins induces structural changes and aggregation . The isomerization rate of aspartic acid is high and causes various serious diseases including Alzheimer s disease and cataract . Herein a method for the comprehensive separation and sensitive detection of isomerized crystallin containing Asp
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Analytical method was developed for isomerized peptides via derivatization and LC MS. Derivatized peptide isomers were separated through a C18 column. This method improved isomerized peptide separation and MS detection sensitivity. This method was applied to analyze the isomerized aspartic acids in a crystallin
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S0021967320303642
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Here we describe a new HPLCMS MS method using a mixed mode stationary phase and a binary gradient of elution for the rapid separation and quantification of AAs in human plasma without derivatization or ion pairing reagent addition . The sample preparation procedure consists in a single dilution step after protein precipitation with sulfosalicylic acid . The proposed method allows for the unambiguous identification and analysis of 52 AAs and related compounds including the separation of isomers and isobars in an 18 min chromatographic run including the conditioning and the equilibration times . AAs were detected by selective reaction monitoring . Internal calibration was used for the quantification of 37 AAs including 25 using the corresponding isotopically labeled internal standards . External calibration was used for five additional analytes . Qualitative detection was achieved for the remaining compounds .
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Amino acid analysis in plasma is of utmost importance in human medicine. Actual methods of amino acid analysis are very time consuming or not specific or not robust. HPLC MS MS using a mixed mode stationary phase avoids pre column derivatization of amino acids. HPLC MS MS using a mixed mode stationary phase avoids ion pairing reagent adding to amino acids
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S0021967320303654
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In this study conventional Quick Easy Cheap Effective Rugged and Safe method was modified by magnetic solid phase extraction for purification pre concentration of eleven estrogens and estrogen mimics from the extracts of pork and chicken muscles prior to dansyl chloride derivatization coupled with ultra high performance liquid chromatography tandem mass spectrometry assay . Dual octadecyl and 2 aminoethyl 3 aminopropyl groups functionalized mesoporous silica core shell magnetic nanoparticles C
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NH. Fe. @mSiO. MNPs were synthesized with good aqueous compatibility. Conventional QuEChERS was modified by efficient and convenient MSPE. Pre column derivatization remarkably enhanced the sensitivity of analytes. It was applied for estrogens and estrogen mimics analysis in pork and chicken. It showed the potential for trace compounds analysis in complex food samples.
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S0021967320303666
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Comprehensive study of enantioselective potential of eight different chiral stationary phases for chiral liquid crystal forming molecules was conducted . The tested columns were polysaccharide based Trefoil AMY1 CEL1 and CEL2 and superficially porous particles packed TeicoShell VancoShell TagShell DMP MaltoShell and NicoShell . To test their enantioselective potential for these separations twenty racemic mixtures of rod like liquid crystalline materials comprising three different types of chiral centres and various other structural differences were used . Mobile phases consisting of supercritical carbon dioxide and alcohol as cosolvent were used selected alcohols were methanol ethanol and propan 2 ol . Effect of acidic and or basic additives on enantioselectivity was also evaluated . Chiral stationary phases based on polysaccharides were found to have the greatest enantioselective potential for rod like molecules that form liquid crystals followed by TeicoShell which proved suitable for enantioseparation of non halogenated liquid crystals with lactic acid based chiral centre .
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SFC is suitable technique for enantioseparation of liquid crystals. Simple mobile phases without additives are sufficient with polysaccharide columns. Additives improve peak shape but scarcely enantioresolution with glycopeptide CSPs. Polysaccharide chiral stationary phases have the greatest enantioselective potential.
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S0021967320303861
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In micellar liquid chromatography the addition of a surfactant to the mobile phase in excess is accompanied by an alteration of its solubilising capacity and a change in the stationary phase s properties . As an implication the prediction of the analytes retention in MLC mode becomes a challenging task . Mixed Quantitative Structure Retention Relationships modelling represents a powerful tool for estimating the analytes retention .
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Predictive ability of 48 mixed QSRR models was compared in terms of. and. Change in the set of input variables had a minor impact on the models performance. Mixed models built by non linear Gradient Boosted Trees showed the highest accuracy. Contribution of steric and dipole dipole interactions to MLC retention was stressed. Fine tuning of molecular geometry is recommended to increase accuracy of final model.
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S0021967320303885
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The variation patterns of transcription factors provide direct information for the states of cell populations which is of significance for biomedical research and clinical diagnostics . Herein we show that through multi channeled isothermal amplification it is feasible to connect DNA based signal transduction with chromatography for multiplexed detection of TFs . The described system is referred to as PAC which includes three major steps
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DNA based signal processing and chromatography is connected. Multi channeled isothermal amplification is realized. Multiplexed detection of p50 p53 AP 1 MITF and c Myc is realized. Profiling of TFs in cells tumors and blood samples is implementable.
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S0021967320303897
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A novel method for screening and quantification of illegal adulterated antidiabetics in hypoglycemic health products was developed by multi dimensional fingerprint profiling analysis . By means of aqueous two phase extraction using aqueous two phase system of butanol water as the extractant 11 common antidiabetics could be effectively extracted to the upper and lower phases respectively . HPLC separation conditions for the extracts from two phases were investigated by multi wavelength detection before and after p nitrobenzoyl chloride and 2 4 dinitrofluorobenzene derivatizations to establish multi dimensional fingerprints . For high accuracy and reliability a hierarchical screening approach to screening illegal adulterated antidiabetics in samples was established by MDFPA and spectral purity examination . Meanwhile detection limits of identification for illegal adulterants were defined by detection limits of spectra . The proposed method exhibited good identification and quantification performances . SLODs LODs and LOQs of 11 antidiabetics were 1.228.37 g g 0.2254.23 g g and 0.75514.10 g g respectively . They had good linearity ranged from 2.0g g to 300.0 g g R
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Screening of illegal adulterants in hypoglycemic health products was developed by HPLC DAD detection. Biphasic extraction of different polar antidiabetics was completed by aqueous two phase extraction. Multi chromatographic conditions were investigated by multi wavelength detection before and after derivatization. Multi dimensional fingerprints were established for highlighting adulterants in sample matrices. A hierarchical MDFPA approach was applied to screening and detection of real samples.
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S0021967320303903
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Antioxidants play an essential role in human health as they have been found to be capable of lowering the incidence of many diseases such as cancer and angiocardiopathy . Currently more attention is paid to natural antioxidants because of the possible insecurity of synthetic antioxidants . Thus the development of efficient techniques or methods to separate antioxidants from natural sources is requested urgently . High speed counter current chromatography is a unique support free liquid liquid chromatographic technique and has been widely applied in the field of separation of natural products . In this review we summarize and analyze the related researches on the application of HSCCC in the separation of various natural antioxidants so far . The purpose of the article is to provide a certain theoretical support for the separation of natural antioxidants by HSCCC and to make full use of advantages of HSCCC in the separation of bioactive components . In particular some key problems associated with the separation strategies the structural categories of natural antioxidants solvent system choices and the application of different elution modes in HSCCC separation are summarized and commented . We expect that the content reviewed can offer more evidence for the development of the field of natural antioxidants separation so as to achieve large scale preparation of natural antioxidants .
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Separation strategies of natural antioxidants by HSCCC are described. The structural classes of separated natural antioxidants by HSCCC are summarized. Solvent systems and elution modes for the separation of natural antioxidants by HSCCC are summarized and discussed. The future outlook of the separation of natural antioxidants by HSCCC are commented.
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S0021967320303915
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Deterministic Lateral Displacement is a microfluidic technique where arrays of micropillars within a microchannel deflect particles leading to size based segregation . We recently demonstrated that applying AC electric fields orthogonal to the fluid flow increases the separation capabilities of these devices with a deflection angle that depends on the electric field magnitude and frequency . Particle deviation occurs in two distinct regimes depending on frequency . At high frequencies particles deviate due to negative dielectrophoresis . At low frequencies particles oscillate perpendicular to the flow direction due to electrophoresis and are also deflected within the device . Significantly the threshold electric field magnitude for the low frequency deviation is much lower than for deflection at high frequencies by DEP . In order to characterize the enhanced separation at low frequencies the induced deviation was compared between the two frequency ranges . For high frequencies we develop both theoretically and experimentally scaling laws for the dependence of particle deviation on several parameters namely the amplitude of the applied voltage particle size and liquid velocity where DEP forces compete with viscous drag . A novel theoretical framework is presented that enables simulation of particle trajectories subjected to DEP forces in DLD devices . Deviation angles predicted by simulations are in very good agreement with experimental data . At low frequencies particles follow the same scaling law but with much lower voltages . This indicates that electrokinetic phenomena other than DEP play an important role in driving particle behaviour . Experiments show that at low frequencies particle motion is affected by quadrupolar electrohydrodynamic flows around the insulating pillars of the DLD array . We quantify the difference between the two frequency regimes and show that an electrokinetic model based only on DEP forces is limited to frequencies of 1 kHz and above .
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Electrokinetics tunes Deterministic Lateral Displacement particle separation. Scaling laws of AC electrokinetic particle separation in DLD devices were identified. Simulations are in excellent agreement with the experimental data at high frequencies. New insights on the particle low frequency AC electrokinetic behaviour are provided.
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S0021967320303927
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The chiral separations of small peptides is an important challenge in the biological and medical sciences because different stereoisomers of chiral drugs can often possess different pharmacological pharmacokinetic and or toxicological activities . Commercially available crown ether chiral stationary phases based on
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Enantioseparation of tetrapeptide Tyr Arg Phe Lys NH. on two crown ether chiral stationary phases is reported. Baseline separation of all eight tetrapeptide enantiomer pairs was achieved. Effect of the ACN content in the mobile phase on retention and enantioselectivity was studied. Efforts to extend the use of chiral crown ether based CSPs in resolution of all sixteen tetrapeptide stereoisomers were made.
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S0021967320303939
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In this study a clean up approach using a two dimensional liquid chromatography consisting of a hydrophilic interaction liquid chromatography column and a reversed phase column was investigated . A fully automated 2D LC system was used and compared with a traditional quick easy cheap effective rugged and safe liquid chromatography method .
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Two dimensional liquid chromatography was compared to a traditional QuEChERS method. Both methods were compared based on a validation protocol with positive detects. Clean up and matrix separation were evaluated with multivariate data analysis. Two dimensional liquid chromatography was proven in European Proficiency Tests.
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S0021967320303940
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Chiral stationary phases have always been research hotspot in enantiomer separation . Currently most of the CSPs are based on silica platform . In this research monodisperse porous glycidyl methacrylate divinylbenzene copolymer particles were designed and prepared . Then the GMA was further reacted with ethylenediamine to introduce amino groups onto the polymer which provide anchoring sites for cellulose derivatives . Herein Cellulose tris was successfully coated onto the polymer microspheres achieving a stable and successful CSP . The porous structure and the surface moieties of the CSPs were studied in detail . The chromatographic separation was optimized . Hexaconazole methyl DL mandelate benzoin and tebuconazole have been successfully separated on the CSP column with column efficiency as high as 10 200 plates m which is comparable with some silica based CSPs . The research has indicated that the poly is a promising candidate for constructing CSPs for chiral separation .
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Mono dispersed porous glycidyl methacrylate divinylbenzene particles were prepared. The particles were aminated for coating with cellulose tris 3 5 dimethylphenylcarbamate . They were used as the chiral stationary phase with high column efficiency. The polymer particles were alternative stationary matrix for chiral separation.
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S0021967320303952
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The topic in the present paper is to prepare molecularly imprinted polymer using the template molecule with low purity . For the first time a surrounding of macromolecular crowding was established to promote the formation of the complex of the template with functional monomer efficiently thus highly pure template molecule was unnecessary . In this study the MIP monolith was synthesized using low purity lactucopicrin as template in place of highly pure one and polystyrene was used as macromolecular crowding agent . 4 Vinylpyridine and ethyleneglycol dimethacrylate were used as functional monomer and crosslinker respectively . Polymerization parameters including the ratio of functional monomer template various template concentrations and PS concentration on the affinity of the resulting MIP were systematically investigated . For the lactucopicrin MIP made with the purity of lactucopicrin of 92 the imprinting factor can be up to 2.2 . The resulting MIP was filled in solid phase extraction cartridge to purify lactucopicrin from the crude extract of
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Crowding surrounding was suggested for preparation of MIP using template molecule with low purity. Crowding surrounding was made up of high molecular PS. The necessity of simultaneous use of PS was proved to prepare MIP with impure template. The MIP made can be used in SPE to purify lactucopicrin from the crude extract.
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S002196732030399X
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In the last decade 3D printing has emerged as a promising enabling technology in the field of analytical chemistry . Fused deposition modelling is a popular low cost and widely accessible technique . In this study RPLC separations are achieved by in situ fabrication of porous polymer monoliths directly within the 3D printed channels . Thermal polymerization was employed for the fabrication of monolithic columns in optically non transparent column housings 3D printed using two different polypropylene materials . Both acrylate based and polystyrene based monoliths were created . Two approaches were used for monolith fabrication
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3D printed channels were successfully developed in house. Monoliths were fabricated in polypropylene 3D printed channels. SEM results showed homogenous monolithic structures. Glass reinforced polypropylene has shown more potential for chromatography. Separation of small molecules were performed in the channels.
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S0021967320304003
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The glutathione trapping assay is commonly utilized for the screening and characterization of reactive metabolites produced by drug metabolism . This study describes a fluorous derivatization method for a more sensitive and selective analysis of reactive metabolites trapped by GSH using liquid chromatography tandem mass spectrometry . In this study the GSH trapped reactive metabolites which were obtained after incubation of the test compounds with human liver microsome in the presence of GSH and NADPH were derivatized using the perfluoroalkylamine reagent through oxazolone chemistry . Since this reaction enabled the selective modification of the
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A fluorous derivatization method was developed for GSH trapped metabolite analysis. The GSH. carboxyl group was selectively perfluoroalkylated by oxazolone chemistry. The fluorous derivatives could be adequately retained on the fluorous LC column. Desirable ESI properties allowed sensitive detection in MS MS scanning mode.
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S0021967320304222
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In this study a multiresidue analytical method was developed validated and applied for quantifying 85 persistent organic pollutants including 38 polychlorinated biphenyls 23 polybrominated diphenyl ethers and 24 organochlorine pesticides from 200 L of human serum . A modified QuEChERS method was applied to minimize the required sample amount and optimize various conditions including the extraction solvent and the number of extractions . The extraction efficiency was optimized using double extraction with an ethyl acetate hexane acetone mixture . Gas chromatography coupled with triple quadrupole mass spectrometry was used for analysis and two different ionization sources electron impact ionization and atmospheric pressure chemical ionization were used to compare their sensitivity . The APCI source employed soft ionization at atmospheric pressure producing abundant molecular ion formation with minimal fragmentation in contrast to extensive fragmentation caused by EI . Of the 85 POPs analyzed 59 target compounds showed lower limits of detection that were two to fifty fold lower in APCI than those determined using EI . The developed method was validated for its detection limit precision recovery matrix effect and accuracy . Its linearity was R
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A multiresidue quantification method was developed for 85 persistent organic pollutants. A modified QuEChERS method was applied to extract POPs in 200 L of human serum. Electron impact ionization and atmospheric pressure chemical ionization were compared. Real samples were analyzed and 32 compounds were detected at significant levels.
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S0021967320304234
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A novel disposable styrene based solid phase microextraction fiber was synthesized for the detection of lipid lowering and antihypertensive drugs in real aquatic environment . Styrene and poly diacrylate were co polymerized on quartz fibers by thermal polymerization in capillary molds . The polymeric fiber possessed a homogeneous dense as well as porous surface showing excellent chemical and mechanical stability . The performance of the fiber was evaluated through the extraction of seven pharmaceuticals by coupling SPME with high performance liquid chromatography tandem mass spectrometry under the optimized extraction conditions . The extraction efficiency of the fiber was up to 278 times of PDMS fiber and the enrichment factors ranged from 55 to 1183 . The limits of detection were in the range from 1.7ngL
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A low cost polymeric solid phase microextraction fiber was prepared. An SPME HPLC MS MS method was developed to detect drugs based on the fiber. Low detection limits high precision and wide linear ranges were obtained. This method was used to detect the target drugs in water samples.
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S0021967320304246
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The enantiomers of a chiral building block to be used in pre clinical manufacturing were separated using supercritical fluid chromatography . Despite an extensive evaluation of different columns and solvent combinations followed by a careful optimization of the chromatographic method the preparative separation suffered from low throughput and high solvent consumption . Consequently additional improvements were necessary . By utilizing stacked injections the chromatographic run time was almost halved and the high solvent consumption was reduced by recycling of the two mobile phase components carbon dioxide and methanol . The carbon dioxide was reprocessed by the SFC instrument whereas methanol was evaporated and recycled from the fractions collected . Hence the originally inefficient separation method was turned into a more sustainable one and the desired enantiopure intermediate was delivered to be used in the following synthesis of the selected candidate drug . Unfortunately when the intermediate was used in the subsequent amide coupling a surprisingly poor yield was obtained . This was caused by an unexpected formation of a stable carbonate salt of the intermediate under the chromatographic conditions used . By removal of the carbonate prior to the amide coupling reaction the manufacturing campaign could be saved and the candidate drug was successfully delivered in time .
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Resolution of enantiomers by supercritical fluid chromatography. Turning an inefficient chromatographic method to a sustainable one. Recycling of mobile phase components. Awareness of equilibria in a CO. based mobile phase. Formation of carbonate salt due to increased apparent pH in the mobile phase.
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S002196732030426X
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A new class of chitosan derivatives with an isopropylthiourea at the 2 position and various carbamates at the 3 6 positions of the glucosamine skeleton was synthesized by the selective thiocarbamoylation of the 2 amino group . The chiral stationary phases were then prepared by coating the obtained chitosan 2 isopropylthiourea 3 6 dicarbamate derivatives onto silica gel . The enantioseparation property of the chitosan based CSPs was assessed with twelve racemates by high performance liquid chromatography . The CSPs displayed a characteristic enantioseparation power which seemed to be significantly affected by the 3 6 substituents of the glucosamine unit . The chitosan derivatives with the 3 6 diphenylcarbamate except for 2 methylphenylcarbamate possessed higher enantioseparation abilities than those with the 3 6 dicyclohexylcarbamate . Compared to other chitosan derivatives with 2 various substituents and commercialized Chiralcel OD the chitosan 2 isopropylthiourea derivatives revealed a relatively higher enantioselectivity for some racemic compounds .
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Synthesis and chiral separation of novel chitosan derivatives. Novel chitosan derivatives with 2 isopropylthiourea and 3 6 dicarbamates. Selective thiocarbamoylation at 2 positions using an isothiocyanate. Racemic compound better resolved on the obtained CSPs than Chiralpak OD. Enantioseparation greatly depends on the substituents.
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S0021967320304271
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An ionic liquid hybrid zwitterionic polymer capillary microextraction column was prepared for the biomimetic enrichment of glycopeptides by one step copolymerization of 2 methacryloyloxyethyl phosphorylcholine and 1 butyl 3 vinylimidazolium bromide in the presence of crosslinker trimethylolpropane trimethacrylate . The resultant monolith was characterized by scanning electron microscopy fourier transform infrared spectroscopy and pore size distribution measurement . Due to the incorporation of zwitterionic MPC owning a unique biomimic structure the monolithic column has large pore size and good biocompatibility exhibiting high extraction efficiency permeability and fast mass transfer to targets . Besides the use of ionic liquids as co monomer in the polymerization endows the monolith with enhanced mechanical stability uniformity and multiple interactions . The prepared column was successfully applied in CME coupled to capillary electrochromatography for the efficient enrichment and separation of glycopeptide antibiotics in foodstuff . The method demonstrated a wide linear range 50.018000.0 g L
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Hybrid capillary microextraction CME column was prepared with biomimic MPC and ionic liquids. CME column exhibits high extraction performance biocompatibility and fast mass transfer to GAs. The extraction mechanism of the hybrid CME column toward GAs was proposed. Hybrid monolith was utilized for the efficient enrichment of GAs in foods by CME coupled to CEC.
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S0021967320304283
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A detailed computer simulation study of the isotachophoretic migration and separation of norpseudoephedrine stereoisomers for cases with the neutral selector added to the leader immobilized to the capillary wall or support or partially present in the separation column is presented . The electrophoretic transport of the analytes from the sampling compartment into the separation medium with the selector the formation of a transient mixed zone the separation dynamics of the stereoisomers with a free or immobilized selector the dependence of the leader pH the ionic mobility of norpseudoephedrine the complexation constant and selector immobilization on steady state plateau zone properties and zone changes occurring during the transition from the chiral environment into a selector free leader are thereby visualized in a hitherto unexplored way . For the case with the selector dissolved in the leading electrolyte simulation data are compared to those observed in experimental setups with coated fused silica capillaries that feature minimized electroosmosis and zone detection with conductivity and absorbance detectors .
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Simulation provides insight into migration dynamics with analyte complexation. Isotachophoretic separation of norpseudoephedrine stereoisomers is simulated. Simulation results are verified experimentally with detectors placed along a capillary. Isotachophoresis in presence of an immobilized selector is depicted. Transition of isotachophoretic zones into a selector free leading electrolyte is described
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S0021967320304295
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Continuous stationary phase gradients for liquid chromatography have been recently shown to be a promising method of altering selectivity . In this work we present the first multicomponent continuous stationary phase gradient for separations involving both reversed phase and strong cation exchange mechanisms . These columns are fabricated using a two step methodology based on controlled rate infusion . First destructive CRI creates a gradient of excess silanol groups along a uniform C
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First fabrication of a continuous multicomponent stationary phase gradient. Destructive and constructive CRI used to fabricate the multicomponent gradients. Gradient stationary phase columns are stable and reproducible. Gradient stationary phase columns separate based on RP and SCX mechanisms.
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S0021967320304301
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Estimation of injection volume during a preparative chiral separation can be challenging . Commonly one attempts to maximize the injection volume to reduce total separation time . The factors that limit increasing injection volume are purity constraint and criterion of product recovery . Standard industrial practice is to successively inject increasing volume of sample mixture until two adjoining peaks touch respective baselines . Separation scientists may spend considerable time and material to detect this injection volume before starting the stack injection run . This increased method development time increases time spent on the instrument resulting in decreased efficiency .
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For maximizing throughput it is important to optimize preparative injection volume. In industry optimum volume is detected iteratively through multiple experiments. This report provides a formula to estimate optimum injection volume. Formula applicable to both HPLC and SFC peak following Langmuir isotherm. Example provided with this report is of a preparative SFC separation.
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S0021967320304325
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The basis of interpretive optimisation in liquid chromatography is the prediction of resolution from appropriate solute retention models . The reliability of the process depends critically on the quality of the experimental design . This work develops validates and applies a general methodology aimed to evaluate the quality of any training experimental design which will be applied in Part II to design optimisation . The methodology is based on the systematic evaluation of the uncertainties associated to the prediction of retention times in comprehensive scans of both isocratic and gradient experimental conditions . It is able to evaluate comprehensively experimental designs of arbitrary complexity . Five common training experimental designs were used to model the retention according to the Linear Solvent Strength and the Neue Kuss equations using a set of 14 sulphonamides of different polarity . The results are presented in terms of relative uncertainties in predictions which provide significant and interpretable results . The magnitude of such uncertainties together with the systematic coherent and logical changes observed at increasing solute hydrophobicity give support to the results . The NK model gave smaller errors and unbiased predictions whereas the LSS model gave rise to lack of fit . Isocratic training designs which are widely accepted as the most informative are confirmed as the best . As a general conclusion gradients are predicted with intrinsically smaller uncertainties independently of the training experimental design . In addition gradients are more insensitive than isocratic predictions with regard to the type of training design used . Isocratic predictions deteriorate quickly with mobile phase composition . This explains the better performance of gradient predictions even with biased models .
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A methodology to evaluate experimental designs is developed validated and applied. Five designs are analysed with two retention models and solutes of varying polarity. Comprehensive meaningful interpretable and coherent results are obtained. Isocratic and multi level gradient training designs are confirmed as the best. Gradient predictions yield smaller and more insensitive uncertainties
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S0021967320304544
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Basic principles are introduced for implementing discovery based analysis with automated quantification of data obtained using comprehensive three dimensional gas chromatography with flame ionization detection GC
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Fisher ratio software is applied to comprehensive three dimensional gas chromatography data. The third separation dimension replaces the mass spectrometric dimension in the data analysis. A new signal ratio algorithm is introduced enabling automated relative analyte quantification. The signal ratio output provides robust quantification with qualitative peak purity information.
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S0021967320304556
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Trapping volatiles is a convenient way to study aroma compounds but it is important to determine which volatile trapping method is most comprehensive in extracting the most relevant aroma components when investigating complex food products . Awareness of their limitations is also crucial . targeted metabolomic approaches were used to determine the volatile profiles of two commercial flavourings . Four trapping techniques were tested as was the addition of salt to the mixture . Comprehensiveness and repeatability were compared and SBSE proved particularly suitable for extracting components such as polysulfides pyrazines and terpene alcohols and provided an overall broader chemical spectrum . SPME proved to be more suitable in extracting sesquiterpenes and DHS in extracting monoterpenes . Adding salt to the sample had only quantitative effects on volatiles as detected by SPME . These results help clarify the advantages and limitations of different trapping techniques and hence deliver a valuable decision tool for food matrix analysis .
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Untargeted metabolomics approaches help understand flavour and chemical composition. Process flavours comprise diverse complex mixtures of volatile compounds. The highest number of volatiles detected was achieved by SBSE. Sorptive extraction is environmentally friendlier than organic solvent extraction
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S0021967320304568
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An imidazolium ionic liquid modified phenolic resin was synthesized using 3 aminophenol as a functional monomer glyoxylic acid as a green cross linker and polyethylene glycol 6000 as a porogen . The obtained ILPR showed better extraction of benzoylurea plant hormones thidiazuron and forchlorfenuron than the unmodified phenolic resin because the imidazolium IL provides more interaction modes with the analytes . ILPR as a tailored adsorbent for solid phase extraction was coupled with high performance liquid chromatography for the simultaneous determination of thidiazuron and forchlorfenuron in cucumbers . Good linearity of the ILPRSPEHPLC method was obtained ranging from 0.0100 to 5.00gg
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A new imidazolium ionic liquid modified resin was prepared via green protocol. The ILPR sorbent exhibited excellent extraction to plant hormones. The ILPR show superior adsorption property than phenolic resin. A new method for detecting of plant hormones in cucumbers was developed.
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S002196732030457X
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Polyimide microspheres assembled by nanosheets were used for bar adsorptive microextraction for the first time . The PI microsphere possessed self organized hierarchical nanostructure large specific surface area 170 m
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Polyimide PI microsphere assembled by nanosheets coated BAE was proposed. PI microsphere had large specific surface area 170 m. g and good thermostability. Nitroaromatic explosives in water samples were quantified by BAE TD GCMS. High enrichment factors 5281410 and low LODs 0.0050.013g L were obtained. The reproducibility of the BAE devices was less than 13.0 RSD for peak area.
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S0021967320304581
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Quantitative analysis of glycans released from glycoproteins using high performance liquid chromatography requires fluorescent tag labeling to enhance sensitivity and selectivity . However the methods required to remove large amounts of excess labeling reagents from the reaction mixture are time consuming . Furthermore these methods including solvent extraction and solid phase extraction often impair quantitative analysis . Here we developed an online sample cleanup procedure for HPLC analysis of 2 aminopyridine labeled glycans using a six port two way valve and two small columns one packed with a strong cation exchange resin and the other comprising ODS silica gel . AP labeled glycans delivered from an injection port were separated from excess AP by passing through an SCX column regulated to 40C . The AP labeled glycans were trapped on an ODS column to further separate them from inorganic contaminants . By changing the valve position after 2 min to connect the ODS column to an analysis column AP labeled glycans trapped in the ODS column were eluted with an acetonitrile containing eluent followed by hydrophilic interaction liquid chromatography separation on an amide column or reversed phase mode separation on a C30 column . This method was successfully used to analyze
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A simple procedure was developed to remove extra 2 aminopyridine using on line SPE. A cation exchange column was used to separate labeled glycans from excess reagents. An ODS mini column with a 6 port valve was used to trap labeled glycans. The method was applicable to HILIC and RP separation of glycan derivatives.
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S0021967320304593
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The additivity assumption underlying Giddings coupling model for the eddy dispersion in laminar flows through heterogeneous media is critically analyzed and a potential solution for its non additivity in the high velocity limit is presented . Whereas the unit cell in Giddings model only consists of a single velocity bias step the unit dispersion cell of the newly proposed model comprises two consecutive velocity bias steps . Consequently the unit cell of this new model allows to account for the occurrence of an internal velocity bias rectification at high reduced velocities and is therefore additive in both the low and high velocity limit .
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The additivity assumption made in current eddy dispersion models fails at high Pe. A checkerboard model is proposed to repair this failure. This model uses a double velocity bias step as its unit dispersion cell. In ordered systems the new model predicts a local dispersion maximum. The model predicts a lower large velocity asymptote than Giddings model.
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S002196732030460X
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We report on a series of high accuracy computational fluid dynamics band broadening simulations in three different 2 D flow systems a 2 D pillar array and 2 D lumped packed bed geometries with different checkerboard velocity bias patterns . These media display a local maximum in the relationship between the eddy dispersion plate height and the mobile phase velocity . The occurrence of such a dispersion maximum has not been reported before but appears to be a characteristic of regular chromatographic media with alternating velocity bias at least in 2 D geometries . This newly observed behavior can be fully understood and modelled using the checkerboard model established in part I of the present study .
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Ordered 2 D chromatographic media also display some degree of eddy dispersion. This eddy dispersion runs through a maximum at an intermediate velocity. The occurrence of this maximum can be modeled with the checkerboard dispersion model. This model can represent the eddy dispersion in both ordered and disordered media.
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S0021967320304623
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Microcystins and nodularin are tumor promoters produced by cyanobacteria and present in surface water . In this work a novel mesoporous metal organic
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material was synthesized via a one step hydrothermal method. This method approach showed advantages of short adsorption time. The sensitivity of the method for nodularin was improved nearly 30 times. The method was applied to analyze microcystins and nodularin in water samples.
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S0021967320304635
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This is the first of a two part study in which we explore the concept of batch chromatography with recycle lag concluding with the design construction and experimental validation of a prototype that embodies the physical realization of this concept . Moreover the apparatus is simple to set up in particular in view of large scale applications . Here the theory behind batch chromatography with recycle lag is revisited and extended with emphasis on the mathematical formulation and procedure for deriving the single column batch analogue of any variant of multicolumn simulated countercurrent chromatography . By resorting to selected examples namely GE Healthcare Bio sciences three column periodic countercurrent chromatography Novaseps sequential multicolumn chromatography and a few hypothetical multicolumn processes we discuss how the theory can be operationalized . Finally we conclude by describing the design of a device or apparatusan eluate recycling device to physically realize the proposed concept . The ERD implements an approximate first in first out method for organizing and manipulating the to be recycled fractions of eluate collected from the chromatography column where the oldest amount fluid or head of the fraction is the first to exit and be recycled to the column .
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The theory behind batch chromatography with recycle lag is revisited and extended. Using a few examples of multicolumn processes we discuss how the theory can be operationalized. The design of an eluate recycling device ERD to physically realize the proposed concept is described. The ERD implements an approximate first in first out method of organizing the eluate fractions. The oldest 1st amount of fluid or head of the fraction is the first to exit the ERD and be recycled to the column.
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S0021967320304647
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Selectivity and high throughput are important for determination of trace level of various organophosphate flame retardants in environmental matrices . In this work three selective monolithic fibers for solid phase microextraction were prepared and evaluated . They are graphene oxide based surface trimethyl phosphate imprinted polymeric fiber GO based surface tri phosphate imprinted polymeric fiber and GO based surface triphenyl phosphate imprinted polymeric fiber . The imprinting factors of GO TMP IPF for TMP GO TECP IPF for TCEP and GO TPhP IPF for TPhP were tested as high as 4.3 4.5 10.3 respectively . The three fibers were bound to a stainless steel wire to assemble a GO based surface molecularly imprinted polymeric fiber array . GO MIP FA SPME device was coupled to gas chromatography flame photometric detector and carried out simultaneous determination of TMP TCEP and TPhP in environmental water . Under the optimal conditions ultralow limits of quantification 1.7 ng L
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Three GO MIPFs for SPME were successfully prepared and characterized. Three GO MIPFs were made to form a fiber array for SPME. GO MIP FA SPME GC FPD method was developed to monitor TMP TCEP and TPhP in water. GO MIP FA SPME GC FPD method was accurate sensitive and high throughput.
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S0021967320304659
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Nowadays sensitive chiral methods are required for the determination of chiral impurities and for assays in biological samples . Supercritical fluid chromatography one of the main techniques to separate chiral molecules can be coupled to MS to provide such sensitive methods . Moreover chiral separation strategies are very useful to reduce the development time and cost of such methods . This study investigates the transfer of an existing non MS compatible screening step into an MS compatible one . The initial step had a cumulative success rate of 100 for 57 tested compounds using methanol or 2 propanol as mobile phase modifier on one of four chiral stationary phases . The additives applied in the original mobile phases i.e . isopropylamine and trifluoroacetic acid negatively affect the ionization in SFC MS and thus need to be replaced . Formic acid acetic acid water ammonia ammonium acetate and ammonium formate were investigated as MS compatible additives in different combinations and concentrations . Only methanol based mobile phases were considered in this study because high system pressures were obtained with isopropanol . The other experimental parameters remained the same as in the initial screening step . The effects of the alternative additives on the obtained resolutions as well as on the global success rate were investigated . The best alternative MS compatible mobile phase contained 0.5 CH
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Transfer from non MS compatible to MS compatible screening step. 18 MS compatible mobile phases are screened. Initial success rate is maintained. More baseline separations are obtained
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S0021967320304660
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Designed more than thirty years ago in order to improve and maximize the discrimination capability of native polysaccharides cellulose and amylose based selectors have shown excellent and unequalled performances for the enantioseparation of chiral compounds . The successful story of these chiral selectors relies on a multi site high ordered chiral platform which is held up by intramolecular hydrogen bonds and makes the polymer able to host and discriminate enantiomers . In this environment both achiral and stereoselective intermolecular noncovalent interactions play a pivotal role and HBs halogen bonds dipole dipole stacking steric repulsive and van der Waals interactions underlie adsorption process and formation of transient diastereomeric assemblies between the polymer and the enantiomer pair . In the last decades advances in computational chemistry and spectroscopic techniques have improved knowledge of noncovalent interactions contributing to decode their functions in chemical systems . Significantly over time the growing interplay between experimental and theoretical approaches has contributed to unravel intermolecular forces underlying selector selectand association and to understand recognition patterns . On this basis this review summarizes seminal and representative studies dealing with noncovalent interactions that function in HPLC enantioseparations promoted by cellulose benzoates and phenylcarbamates of amylose and cellulose . The importance of integrating theoretical and experimental approaches to profile mechanisms and interaction patterns is highlighted by discussing focused case studies . In particular the advantageous utilization of electrostatic potential
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Structural features of polysaccharide derivatives are briefly summarized. Functions of noncovalent interactions in polysaccharide derivatives. Role of intra and intermolecular noncovalent interactions. Computer aided approaches for studying chiral recognition mechanisms
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S0021967320304684
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Deep eutectic solvents were used as an extractant for the determination of pyrethroidsin environmental water and tea beverage samples . Three different acids were chosen as hydrogen bond donors for preparation of DESs and decanoic acid was optimal because of its high recovery . Factors affecting relative recovery were optimized individually including salt addition surfactant addition extraction temperature DES amount and sample volume etc . Under the optimized experimental conditions the relative recovery of pyrethroids was from 89.3 to 97.7 with relative standard deviation values ranging from 1.75 to 2.73 . The linearcorrelationcoefficient ranged from 0.9981 to 0.9992 and the linear range was between 1.9 and 500 g L. Based on a signal to noise ratio of 3 1 the limit of detection values were 0.56 to 1.24 g L. The enrichment factor ranged from 92 to 105 . In conclusion good extraction efficiency was achieved in tea beverage samples under the optimized conditions .
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Uniform and mechanically free dispersion method. Green and economic extractant. Short extraction time.
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S0021967320304696
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Oxylipins the oxidation products of polyunsaturated fatty acids are important signaling molecules in living organisms . Some of them have pro inflammatory properties while others act as pro resolving agents . Oxylipins also play a major role in platelet biology and the progression of thrombo inflammation . Depending on their structure they may be pro thrombotic or anti thrombotic . For an unbiased biological interpretation a detailed analysis of a broad spectrum of oxylipins including their stereoisomers is necessary . In our work we developed for the first time an enantioselective UHPLC ESI MS MS assay which allows quantifying individual oxylipin enantiomers . The assay made use of a sub 2m particle based amylose chiral stationary phase under MS compatible reversed phase conditions . It covered 19 enantiomeric pairs of oxylipins and one diasteromeric pair of a lipid mediator 2 pairs of hydroxyoctadecadienoic acids 6 pairs of hydroxyeicosatetraenoic acids 5 pairs of hydroxyeicosapentaenoic acids 3 pairs of hydroxydocosahexaenoic acids and one pair of each resolvins D1 hydroxyeicosatrienoic acid hydroxyoctadecatrienoic acid and dihydroxyeicosatetraenoic acid . The new method is fast and showed outstanding peak resolution for most of the isomeric pairs . Excellent method sensitivity was obtained by using a triple quadrupole instrument as a detector in a targeted selected reaction monitoring mode . The applicability of the method was verified by preliminary validation . It was then applied to analyze oxylipins produced by autoxidation of polyunsaturated fatty acids in air . Multiple oxylipins were found in each of the samples as racemic mixtures and served as reference substances for identification . Finally the new enantioselective UHPLC method was applied to analyze releasates from platelets in resting state and following activation with thrombin . The highest abundant oxylipin in the platelet releasate was 12
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Enantioselective UHPLC MS MS method for chiral oxylipins developed. Chiral separation of HODEs HETEs HEPEs HDoHEs HETrEs HOTrEs DiHETEs Resolvins D1. Screening of different methods with sub 2m Chiralpak IA U and IC U columns. Quantification of racemic mixtures from PUFA autoxidation. Analysis of platelet releasates from resting and thrombin activated platelets.
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S0021967320304726
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In most cases determination of binding constant for analyte cyclodextrin complexes in capillary electrophoresis is investigated by affinity capillary electrophoresis using a UV detector . The limitations induced by the UV detector include the difficulty of dealing with poor chromogenic analytes and more generally with any analyte presenting strong affinity towards the cyclodextrin i.e . for which the prerequisite to work with analyte concentration much smaller than those of the CD is difficult to fulfill the impossibility of studying non chromogenic analyte . In this paper two simple methodologies were developed to overcome these limitations . Regarding the analytes which present poor UV absorbance and or very high CD affinity a methodology using an algorithmic data treatment and taking into account the real analyte concentration in the capillary at the determined migration times allows to correctly estimate the binding constants even if the experimental prerequisite is not complied . Moreover it is proved that classical linearization treatment by picking the migration time of the infinite diluted analytes also provide satisfactory results . Regarding UV transparent analyte a competitive methodology combined with algorithmic data treatment allows the determination of their affinity towards cyclodextrins . Last the applicability of the described competitive method is extended to the study of interaction between two neutral partners which is another well known limitation of ACE .
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Algorithmic treatment and competitive experiments extend the applicability of the ACE UV. Binding of strong transparent and or neutral substrates with CD can be determined. Determining the migration times at peak start was relevant for classical linearization. Global algorithmic treatment estimates the dilution of the sample molecules in capillary.
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S0021967320304738
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Illegal dietary supplements adulterated with phosphodiesterase type 5 inhibitors are increasingly widely distributed through internet markets and underground routes . For this reason it demands development of reliable screening methods to determine a wide range of PDE 5i drugs in various types of dietary supplements . Herein we developed a screening method using gas chromatography mass spectrometry for simultaneous detection of 53 PDE 5i drugs in supplements . Common formulations of supplements with complicated matrices were treated by simple liquidliquid extraction and trimethylsilyl derivatization . With the aid of TMS derivatization 53 PDE 5i drugs could be successfully separated and detected within 15min using a short microbore GC column . Moreover owing to enhanced detection sensitivity and selectivity of PDE 5i TMS derivatives 0.5mg of sample was sufficient to screen and confirm targeted PDE 5i drugs . In this study specific common ions according to structural characteristics of PDE 5i drugs were found under the electron ionization of their TMS derivatives . These specific common fragments could reflect the common pharmacophores for 4 classes of PDE 5i drugs . Based on characteristic EI fragment ions extracted common ion chromatograms and discriminant analysis were effectively used for reliable screening and classification of various types of PDE 5i drugs . Specific ECICs and DA using characteristic EI fragments here will aid in identification of newly emerging PDE 5i counterfeits in supplements . This study will be helpful to supervise illegal adulteration of PDE 5i drugs in dietary supplements to protect public health and consumer safety .
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Development of a GCMS method to screen 53 PDE 5i drugs in dietary supplements. Microscale sample preparation combined with simple LLE and trimethylsilylation. First description of characteristic common EI fragment ions of PDE 5i TMS derivatives. Construction of ECICs and discriminant analysis DA based on specific common ions. Reliable screening and classification of PDE 5i in supplements using ECICs and DA.
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S002196732030474X
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This is the second of a two part study in which we explore the concept of batch chromatography with recycle lag concluding with the design construction and experimental validation of a prototypean eluate recycling device that embodies the physical realization of this concept . The ERD implements an approximate first in first out method of organizing and manipulating the to be recycled fractions of eluate collected from the chromatography column where the oldest amount fluid or head of the fraction is the first to exit and be recycled back to the column . Moreover the apparatus is simple to set up in particular in view of large scale applications . Here we detail the construction of the ERD and assembly of a setup to interconnect the ERD and a chromatography column . Through the coordinated operation of two way valves and two position six port switching valves it is possible to implement a diverse set of configurations or operating modes interconnecting the chromatography column and the ERD . The setup is validated experimentally with success using the separation of a nucleoside mixture by reversed phase chromatography as a model problem . It is also shown that by redesigning the fluid distributor using 3D printing technology the ERD performance can be improved .
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The theory behind batch chromatography with recycle lag is revisited and extended. The design of an eluate recycling device ERD to physically realize the proposed concept is described. The construction of the ERD and assembly of a setup to interconnect the ERD and a chromatography column is detailed. The setup is validated experimentally with success using the separation of a nucleoside mixture by reversed phase chromatography. By redesigning the fluid distributor using 3D printing technology the ERD performance can be improved.
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