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S0021967320304751
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Non ionic surfactants such as polysorbates known as Tween 20 and Tween 80 are routinely used within the healthcare and pharmaceutical industry to enhance solubility . This work focuses on analysing the two aforementioned polysorbates each considered at three purity levels with four model compounds across the critical micellar concentration range for each surfactant . Such data is of interest to investigate the influence of micelle formation upon compound polysorbate interaction . Two analytical techniques were utilised namely spectroscopic solubility determination and micellar liquid chromatography . In all cases it was apparent that the maximum solubility for all four compounds increased substantially at concentrations greater than the CMC and that in most cases a different retention profile was observed using MLC once the CMC had been exceeded . This paper is the first to have used such techniques to investigate the behaviour of these polysorbates over a series of concentrations and three levels of polysorbate purity . The findings indicate that the solubilisation potential of polysorbates differs once the CMC has been surpassed and is dependent upon the level of purity selected i.e . compound surfactant interactions are partially a consequence of the presence of micelles rather than monomer as well as polysorbate purity . Thus formulators should include such polysorbates at optimised concentrations and purity if they wish to maximise their solubilisation potential .
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Micellar liquid chromatography MLC was undertaken using polysorbates and four compounds. Each compound displayed a different retention profile above the CMC. The maximum solubility for the compounds increased substantially at concentrations greater than the CMC. Solubilisation by polysorbates is dependent upon the level of polysorbate purity selected.
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S0021967320304763
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In the present study separation of enantiomers of some chiral neutral basic and weakly acidic analytes was investigated on the chiral stationary phase made by covalent immobilization of amylose tris onto aminopropylsilanized silica in nano liquid chromatography in aqueous methanol or acetonitrile mixtures . It has been shown that similar to high performance liquid chromatography and supercritical fluid chromatography this chiral selector is useful for separation of enantiomers of neutral basic and acidic analytes also in nano LC . In comparison to our previous research in which the chiral selector was bonded on native silica in this study the CS was immobilized on APS silica in order to improve chromatographic performance towards basic analytes . In fact some improvement was observed and surprisingly not only for basic but also for neutral and acidic analytes . Again quite unexpectedly almost no electroosmotic flow was observed in capillaries packed with ca . 20 amylose tris immobilized onto APS silica although the same APS silica before attachment of chiral selector exhibited significant EOF . In order to generate EOF in the capillaries with the CSP and enable capillary electrochromatographic experiment on it the short segment of the capillary column was packed with APS silica without chiral selector . The EOF in such capillary enabled CEC experiment and some preliminary results are reported here .
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A novel polysaccharide derivative bonded to aminopropylsilica was studied in nano LC. Enantiomers separation of basic acidic and neutral compounds was obtained. Segmented capillary was used for generation of the electroosmotic flow
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S0021967320304775
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Plant hormones are a type of pesticide that can potentially affect human health . Therefore their quantitative detection is particularly important . In this study a green and economic method for the simultaneous extraction and determination of four PHs namely thidiazuron forchlorfenuron 1 naphthylacetic acid and 2 naphthoxyacetic acid in watermelon juice was developed by using m aminophenolureaglyoxal resin as the adsorbent for pipette tip solid phase extraction coupled with liquid chromatography . The resin was synthesized via a simple and green process . The synthesized resin possesses multiple functional groups high adsorption capacity larger specific surface area than the ureaglyoxal resin and m aminophenolglyoxal resin and can be regenerated easily . The PT SPE device is simple cheap and easy to obtain and the adsorbent dosage is only 5.0mg . The proposed method has a wide linear detection range high recovery good precision and high sensitivity and satisfies the measurement requirements for detecting trace levels of PHs in fruits and vegetables .
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Amino functionalized resin MAPUGR with rich functional group was synthesized. Low toxicity glyoxal instead of carcinogenic formaldehyde for green synthesis. MAPUGR has the advantages of large adsorption capacity and easy regeneration. Rubber suction ball assisted PT SPE save resources and improve reproducibility. MAPUGRPT SPEHPLC detects four PHs in watermelon juice simultaneously.
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S0021967320304787
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A method for the preparation of an on column ESI emitter used as the sheathless interface for coupling capillary electrophoresis with mass spectrometry was developed . The emitter was directly fabricated at the outlet end of the separation capillary which was etched with HF solution to a symmetrical tip . The tip was covered with a small piece of gold foil which was fixed by epoxy resin glue for electrical contact . Such a prepared ESI emitter can produce a stable ESI signal over the wide range of flow rate from 50nL min to 800nL min . The performance of the CE MS with the sheathless interface was evaluated by using the separation of four alkaloids . It was found that the strong electroosmotic flow produced by the multiple polyelectrolyte coating on the capillary is necessary for maintaining a stable MS signal . Effect of the running buffer composition concentration and the CE separation voltages on the ESI signal strength were investigated . The absolute detection limits for the alkaloids was determined as fmol level . Moreover the CE MS was applied for the analyses of trypsin digestion of cytochrome
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A simple but robust sheathless interface for coupling CE MS has been developed. The symmetrical tip obtained by HF etching was cover by a piece of gold foil. It can produce a stable MS signal over the flow rate range 50 to 800nL min. It can continuously work for at least 180h. The LOD for the alkaloids was determined as fmol level.
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S0021967320304799
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In this study amylose and cellulose phenylcarbamate based chiral columns with different chiral selector chemistries were compared to each other for the separation of enantiomers of basic chiral analytes in acetonitrile and aqueous acetonitrile mobile phases in HPLC . For two chemistries the amylose based columns with coated and immobilized CSs were also compared . The comparison of CSs containing only electron donating or electron withdrawing substituents with those containing both electron donating and electron withdrawing substituents showed opposite results for the studied set of chiral analytes in the case of amylose and cellulose derivatives . Along with the chemistry of CS the focus was on the behavior of polysaccharide phenylcarbamates in acetonitrile versus aqueous acetonitrile as eluents . In agreement with earlier results it was found that in contrast to the commonly accepted view polysaccharide phenylcarbamates do not behave as typical reversed phase materials for basic analytes either . In the range of water content in the mobile phase of up to 2030 v v the behavior of these CSs is similar to hydrophilic interaction liquid chromatography type adsorbents . This means that with increasing water content in the mobile phase up to 2030 v v the retention of analytes mostly decreases . The important finding of this study is that the separation efficiency improves for most analytes when switching from pure acetonitrile to aqueous acetonitrile . Therefore in spite of reduced retention the separation of enantiomers improves and thus the HILIC range of mobile phase composition offering shorter analysis time and better peak resolution is advantageous over pure polar organic solvent mode . Interesting examples of enantiomer elution order reversal were observed for some analytes based on the content of water in the mobile phase on Lux Cellulose 1 and Lux Amylose 2 columns .
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Ranking of amylose and cellulose phenylcarbamate based chiral columns. Unusual dependence of analyte retention and peak efficiency on the eluent composition. Enantiomer elution order reversal based on water content in the mobile phase.
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S0021967320305045
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In this work an easy and fast procedure for the selective multiresidue determination of 14 highly polar pesticides and metabolites in beverages is presented . After an initial sample dilution the extract is shaken and centrifuged further diluted and then injected directly into the LC MS MS system using hydrophilic interaction liquid chromatography and tandem mass spectrometry . No clean up procedure was needed . The method was validated according to the current European guidelines for pesticide residue analysis in food and feed and linearity limits of detection and quantification matrix effects trueness and precision were assessed . For plant based milk wine and beer samples 10 11 and 12 analytes respectively out of 14 were fully validated at 10 g kg
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Selective multiresidue method for direct determination of 14 highly polar pesticides. Sample treatment was performed in four steps dilution shaking centrifugation and extra dilution before injection. No clean up was applied for any matrix. Limits of quantification of 0.01 mg kg. were achieved for most of the pesticides.
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S0021967320305057
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Affinity chromatography is generally regarded as a powerful tool allowing the single step purification of recombinant proteins with high purity and yields . However for most protein products affinity purification methods for industrial applications are not readily available mainly due to the lack of specific and robust natural counterparts that could function as affinity ligands . In this study we explored the applicability of nanobody based peptide tag immunorecognition systems as a platform for affinity chromatography . Two typical nanobodies that are capable of recognizing specifically a particular peptide tag were prepared through prokaryotic expression and proved to be able to bind with nanomolar affinity to their cognate tag fused to enhanced green fluorescent protein . Through an epoxy based immobilization reaction the two nanobodies were coupled on a Sepharose CL 6B matrix under the same conditions . The remaining antigen binding activity of the immobilized BC2 nb and Syn2 nb was determined to be 83.1 and 42.9 yielding the resins with the dynamic binding capacity of 21.4mg mL and 5.9mg mL respectively . The immobilized affinity ligands exhibited high binding specificity towards their respective target peptides yielding a product purity above 90 directly from crude bacterial lysates in one single chromatographic step . However for the both affinity complexes desorption has been found difficult and effective recovery of the bound products could be only achieved with competitive elution or after employing harsh conditions such as 10mM NaOH solution which will compromise the reuse cycles of the affinity resins . This study shows the potential of nanobody based affinity chromatography for efficient purification of recombinant proteins especially from complex feedstocks and reveals the primary issues to be addressed to develop a successful application .
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Nanobody based affinity purification of proteins through fused peptide tag. Nanobodies that recognize specific peptide tags can be well expressed in. Target proteins can be harvested with high purity directly from crude bacterial lysates. This strategy can serve as a potential affinity purification platform.
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S0021967320305069
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Processing of traditional Chinese medicine can enhance the efficacy and or reduce the toxicity . Currently available approaches regarding TCM processing generally focus on a few markers rendering a one sided strategy that fail to unveil the involved global chemical transformation . We herein present a strategy by integrating enhanced multicomponent characterization untargeted metabolomics and mass spectrometry imaging to visualize the chemical transformation and identify the markers associated with the wine steaming of Ligustri Lucidi Fructus as a case . An ultra high performance liquid chromatography quadrupole Orbitrap mass spectrometry based polarity switching precursor ions list including data dependent acquisition approach was developed which enabled the simultaneous targeted untargeted characterization of 158 components from LLF via one injection analysis . Holistic continuous and time dependent chemical variation trajectory among different processing time for LLF was depicted by principle component analysis . Pattern recognition chemometrics could unveil 20 markers among which the peak area ratios of eight components to oleuropein aglycone used as an internal standard were diagnostic to identify the processed from the raw LLF . Four markers showed an increasing trend while another four decreased in LLF after processing . MSI visualized the spatial distribution in the fruit and indicated consistent variation trends for four major markers deduced by the untargeted metabolomics approach . This integral strategy in contrast to the conventional approaches gives more convincing data supporting the processing mechanism investigations of TCM from a macroscopic perspective .
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We report an integral strategy to study chemical variation of TCM by processing. Totally 158 components were characterized from Ligustri Lucidi Fructus LLF . Eight markers were discovered to differentiate between the raw and processed LLF. Mass spectrometry imaging visualized the distribution of the discovered markers.
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S0021967320305070
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This work describes a sensitive and rapid analytical method for trace determination of polycyclic aromatic hydrocarbons in cosmetic samples . The proposed method is based on stir bar sorptive dispersive microextraction . A magnetic composite made of CoFe
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A sensitive analytical method to determine PAHs in cosmetic samples is presented. Trace levels of analytes can be determined by this method. Analytes are extracted by using SBSDME and analyzed by GC MS. Small volumes of organic solvents and short analysis time are needed. This work expands the potential of SBSDME to other analytes and sorbent phases.
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S0021967320305082
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Two isomeric biphenyl neolignans magnolol and honokiol are considered as constituents responsible for the healing effect of magnolia bark a traditional Oriental medicine . To survey the increasing number of dietary supplements that contain magnolia bark or its extract an affordable quantitative thin layer chromatography densitometry method was developed . The methanol extracts were analyzed on the silica gel plates after manual sample application using
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Quantification of magnolol and honokiol in dietary supplements by affordable TLC UV. Bioactivity profiling of dietary supplements by HPTLC effect directed analysis. HPTLC EDA combined with HPTLC ESI MS. Magnolol honokiol piperine and daidzein as bioactive constituents. Stability assessment of the analytes by 2D HPTLC MS.
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S0021967320305094
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Detection of endogenous anabolic androgenic steroids misuse is a major challenge in doping control analysis . Currently a number of endogenous steroids which constitute the steroid profile are quantified using gas chromatography . With this methodology only the sum of the free and glucuronidated steroids is measured together . A dilute and shoot LC MS method which is compliant with the quality requirements for measuring EAAS established by the World Anti Doping Agency was developed and validated containing glucuronidated and sulfated steroids in order to gain some extra information and to expand the existing steroid profile . The developed method is to the best of our knowledge the first method to combine both steroid glucuronides and sulfates which is compliant with the quality standards of the technical document on EAAS established by WADA . The first advantage of this new steroid profile is the reduced sample preparation time as it is a direct injection method of diluted urine . A second advantage is the ability of the used gradient to separate 5 androstane 3 17 diol 3 glucuronide 5 androstane 3 17 diol 17 glucuronide 5 androstane 3 17 diol 3 glucuronide and 5 androstane 3 17 diol 17 glucuronide allowing to gain specific information on these isomers which can not be accomplished in GC MS screening due to hydrolysis . This steroid profile also contains free testosterone 5 androstane 3 17 dione and 5 androstane 3 17 dione as markers of degradation . In total 17 compounds and 10 isotopically labelled internal standards are included in this method .
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A dilute and shoot steroid profiling method is validated. The developed steroid profile contains intact steroid conjugates. Information about phase II metabolism expands the existing steroid profile. WADA s quality criteria for measuring endogenous anabolic steroids are met
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S0021967320305100
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The separation of the enantiomers of mepromazine promethazine thioridazine and alimemazine was studied by nonaqueous capillary electrophoresis in the presence of cyclodextrins using 1 M acetic acid and 50 mM ammonium acetate in methanol as background electrolyte . Heptakis cyclodextrin heptakis cyclodextrin and octakis cyclodextrin were the most effective chiral selectors for mepromazine promethazine and alimemazine . Subsequently a method for the determination of dextromepromazine as chiral impurity of levomepromazine was developed employing quality by design principles . Using HDMS CD as selector a fractional factorial resolution V design was employed for evaluating the knowledge space while a central composite face centered design provided further method optimization and the basis for the computation of the design space by Monte Carlo simulations . The final experimental conditions included a 30 40.2 cm fused silica capillary with 75 m inner diameter and a background electrolyte composed of 0.75 M acetic acid and 55 mM ammonium acetate in methanol containing 27.5 mg mL HDMS CD . The applied voltage was 22 kV and the capillary temperature was 15C . Following method robustness testing via a Plackett Burman design the method was validated for dextromepromazine in the range of 0.01 to 3.0 relative to a concentration of 0.74 mg mL levomepromazine and applied to the analysis of reference standards of the European Pharmacopoeia and commercial tablets . The assay also allowed the detection of levomepromazine sulfoxide although the quantitation of the compound was hampered by the poor peak shape of the late migrating diastereomer .
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Enantioseparation of phenothiazines by negatively charged cyclodextrins in methanolic background electrolytes. Application of analytical quality by design QbD in method development. Quantitation of dextromepromazine at the 0.01 level. Application to the analysis of drug substance and formulations
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S0021967320305112
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Untargeted metabolomics can be a great tool for exploring new scientific areas however wrong metabolite annotation questions the credibility and puts the success of the entire research at risk . Therefore an effort should be made to improve the quality and robustness of the annotation despite of the challenges especially when final identification with standards is not possible .
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Oxidized lipids in the untargeted metabolic profiling of neuroendocrine tumors NETs. RP LC ESI QTOF MS MS analysis in positive and negative ESI ion mode. An increase of the concentration of the HETEs and oxLPCs in NET s plasma. HETEs annotation through spectral matching. oxLPCs annotation via reference native forms and mechanistic fragmentation pathways
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S0021967320305124
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Atmospheric amines contribute to the nucleation and initial growth of new particles as well as secondary organic aerosol formation influencing the radiative balance of the Earth s atmosphere . In this study we develop an ion chromatography method for separating and quantifying the nine most abundant amines methylaminium MMAH
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Nine amines are separated and quantified from common inorganic species in atmospheric aerosols. Dimethylamine and trimethylamine are successfully separated using acetonitrile as eluent additive. The IC method is robust for quantifying amines and inorganic cations in both urban and marine aerosols.
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S0021967320305136
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In this study 31 racemates of N FMOC amino acids with different chemico physical characteristics have been successfully resolved in fast enantioselective chromatography on recently developed zwitterionic teicoplanin chiral stationary phases . The CSPs were prepared by covalently bonding the teicoplanin selector on fully porous particles of narrow dispersion particle size distribution and superficially porous particles . Both the zwitterionic teicoplanin CSPs have proved to be ideal media for the separation of this important class of compounds . In particular the zwitterionic CSP prepared on superficially porous particles exhibited superior enantioselectivity and resolution compared to that made of fully porous particles in virtue of more favorable thermodynamics . The zwitterionic nature of these CSPs allowed avoiding the annoying effect of Donnan s exclusion of enantiomers from the stationary phase . This effect on the opposite was frequently observed on a commercial teicoplanin CSP employed for comparative purposes . Noticeably on the zwitterionic teicoplanin CSPs by using either acetonitrile or methanol rich mobile phases it was possible to favor speed over enantioresolution and vice versa . This work gives further replies to the request for rapid determination of enantiomeric excess of N FMOC proteinogenic AAs typically used as preferred chiral synthons in the solid phase synthesis of therapeutic peptides .
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31 racemates of N. FMOC proteinogenic amino acids were successfully resolved. Comparison between zwitterionic teicoplanin based CSPs and commercial ureido based CSP. fast enantioseparations
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S0021967320305148
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On line coupled high performance liquid chromatography gas chromatography flame ionization detection used for determining mineral oil aromatic hydrocarbons in foods particularly in certain oils and fats may be disturbed by interfering olefins present as natural food components or resulting from raffination of the oils and fats . While some interference can be coped with by disregarding their peaks others overload GC to the extent of obscuring the MOAH or form humps which need to be distinguished from the hump formed by the MOAH . In the latter cases it is necessary to remove these interferences prior to HPLC GC analysis . So far epoxidation of the olefins to increase their retention time beyond that of the MOAH in HPLC is the best method available though imperfect by causing some loss of MOAH and sometimes incomplete removal of the interference . Two methods are re evaluated preference is given to a slightly modified version of that proposed by Nestola and Schmidt . The performances are comparable the losses of MOAH are similar and with both methods not all interfering olefins may be removed from refined edible oils . However the Nestola Schmidt method has practical advantages the main ones being that no cooling is necessary and no solvent needs to be evaporated which facilitates automation . Potential residual interferences must be recognized and subtracted which can be by the characteristics of the hump they form in HPLC GC FID by GCxGC FID or by GCxGC MS using characteristic mass fragments .
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Epoxidation for MOAH analysis only if required owing to losses of MOAH. For refined edible oils removal of interferences may be incomplete. Residual interferences can be recognized the characteristics of the hump. GCxGC supports recognition of residual interferences. The Nestola Schmidt method is technically preferable.
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S002196732030515X
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The quest for ligands alternative to Protein A for the purification of monoclonal antibodies has been pursued for almost three decades . Yet the IgG binding peptides known to date still fall short of the host cell protein logarithmic removal value set by Protein A media . In this study we present an integrated computational experimental approach leading to the discovery of peptide ligands that provide HCP LRVs on par with Protein A . First the screening of 60 000 peptide variants was performed using a high throughput search algorithm to identify sequences that ensure IgG affinity binding . Select sequences WQRHGI MWRGWQ RHLGWF and GWLHQR were then negatively screened
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positive and negative selection of IgG binding peptides. Static binding capacity 50 mg IgG per mL of resin. Dynamic binding capacity of up to 36 mg mL under fast flow. Peptide WQRHGI provides a HCP LRV 2.7. High stability of the peptide ligands over 100 cycles of reuse.
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S0021967320305161
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In the present study a novel strategy based on unidirectional freezing and atom transfer radical polymerization combined with activator regenerated by electron transfer was applied to synthesizing orderly macroporous monolithic column with restricted access property in a 1000L pipette tip . The RA column was composed of hydrophobic inner column poly styrene
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Monolithic column with long and aligned channels prepared in pipette tip. ARGET ATRP method under unidirectional freezing was applied. Poly hydroxyethyl methacrylate chains grafted on the surface of monolithic column. Monolithic tip fixed to syringe for directly extracting drugs from rat plasma. Restricted access SPE HPLC UV for monitoring Magnolia bark phenols in rat plasma.
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S0021967320305173
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Effect directed analysis is increasingly used in environmental monitoring to detect and identify key toxicants . High performance thin layer chromatography has proven to be a very suitable fractionation technique for this purpose . However HPTLC is limited in its separation efficiency . Thus separated fractions could still contain many different components and identification of the effective substances remains difficult . Therefore in this study a workflow for selective EDA with two dimensional HPTLC in combination with high performance liquid chromatography high resolution mass spectrometry was developed . The aim of the workflow was the stepwise reduction of the sample complexity in order to reduce the number of signals that could be responsible for the measured effects . As a consequence the identification of effective substances should be facilitated . The acetylcholinesterase inhibition assay for the detection of potential neurotoxic compounds was applied for biotesting . The transfer of effective zones from the first to the second dimension and also to the mass spectrometric measurement was enabled by extraction .
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Effect directed analysis with two dimensional thin layer chromatography. Acetylcholinesterase inhibition assay to detect potential neurotoxic effects. Combination with mass spectrometry for identification of effective compounds. Prioritization of effective compounds through stepwise reduction of sample complexity. Identification of potential neurotoxic compounds in surface and waste water.
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S0021967320305185
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In this work the use of different solvents and temperatures was explored aiming to evaluate their influence on the enantioseparation of pesticides by HPLC in polar organic conditions employing a column containing immobilized amylose
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Evaluation of enantioseparation on Chiralpak IG column in polar organic conditions. Additives on chiral separations Effect of chemical nature and concentration studies. Study of temperature and mobile phase effects on 17 pesticides enantioseparation. Thermodynamic functions associated to the enantiorecognition process were estimated. Enantioseparation process was discussed from a thermodynamic point of view.
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S0021967320305197
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Synthetic opioids are responsible for numerous overdoses and fatalities worldwide . Currently fentanyl and its analogs are also mixed with heroin cocaine and methamphetamine or sold as oxycodone hydrocodone and alprazolam in counterfeit medications . Microextraction techniques became more frequent in analytical toxicology over the last decade . A method to simultaneously quantify nine synthetic opioids fentanyl sufentanil alfentanil acrylfentanyl thiofentanyl valerylfentanyl furanylfentanyl acetyl fentanyl and carfentanil and two metabolites norfentanyl and acetyl norfentanyl in urine samples by microextraction with packed sorbent and liquid chromatographytandem mass spectrometry was developed and validated . A multivariate optimization was performed to establish the number and speed of draw eject sample cycles and the extraction solvent . The best extraction condition was eight draw eject sample cycles with a velocity of 3.6 L sec and acetonitrile as elution solvent . Linearity was achieved between 1 to 100 ng mL with a limit of detection of 0.1 ng mL and limit of quantification of 1 ng mL . Imprecision and bias were less than 12.8 and 5.7 respectively . The method had good specificity and selectivity when challenged with 10 different matrix sources and 36 pharmaceuticals and drugs of abuse at concentrations of 100 or 500 ng mL . The method was successfully applied to authentic urine samples . MEPS was an efficient semi automatic extraction technique requiring small volumes of organic solvents and sample . The cartridges can be cleaned and reused .
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Synthetic opioids in urine by MEPS extraction. Multivariate optimization. Semi automatic sample preparation technique
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S0021967320305203
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Natural estrogens and the synthetic estrogen are endocrine disruptors harmful to aquatic wildlife . The European Commission included these molecules in the surface water Watch Lists issued in 2015 and 2018 under the Water Framework Directive regarding emerging aquatic pollutants proposing maximum detection limits of 0.035 ng L for EE2 and 0.4 ng L for E1 and E2 . Attaining these limits represents a challenge even with the most up to date analytical tools in particular in surface water . A two step sample preparation involving a preliminary extraction of a whole water sample on a solid phase extraction disk and further purification on a Florisil SPE cartridge was optimized . The purified extract was derivatized subsequently and quantified by LC MS MS . The main goal was to maximize the recoveries to achieve the very low LODs required by the European Watch Lists . The method was fully validated in seven surface water . The LODs calculated were below the maximum acceptable limits required by the European Commission .
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Estrogenic compounds determination on surface water samples. Comparison of disk and cartridge SPE sorbents. Method optimization to maximize sensitivity in agreement with EU requirements. LODs below the recommended by the EC Decision 2018 840. Validation performed on 7 surface water samples
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S0021967320305227
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Analysis and control of stereoisomers is a major task in pharmaceutical analysis and is a greater challenge when compounds with multiple chiral centers are concerned . HPLC and SFC are commonly used for stereoisomer analysis in drug development typically starting with chiral method screening . Although method screening for compounds with a single chiral center has been well studied for 5 m polysaccharide stationary phase particles there are fewer reports on method screening for compounds with MCC and smaller particle sizes . In this study we systematically evaluated the impact of key parameters in chiral method screening including column particle size nature of the chiral selector binding mobile phase elution mode and separation approach . A diverse set of pharmaceutical compounds with MCC and a SCC were studied . We found that the screening strategies differ between MCC and SCC compounds due to the difference in the recognition mechanism involved . Furthermore we have developed an effective screening strategy with OD 3 AD 3 and IG 3 columns for SCC compounds which achieves larger than 90 success rate and a combination of OD 3 AD 3 IG 3 IC 3 and AS 3 for MCC compounds which offers the best coverage .
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Evaluation of method screening of compounds with multiple and single chiral center s . Evaluation of a total of 66 individual single chiral center stereoisomers and 65 multiple chiral center stereoisomers. Evaluation of particle size coated vs. immobilized isocratic vs. gradient and SFC vs. HPLC for final selection of screening conditions. Difference in chiral screening strategies for compounds with multiple chiral centers and single chiral center was identified. Development of a fast HPLC screening strategy for multiple chiral center and single chiral center compounds with high success rates.
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S0021967320305331
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A three dimensional HPLC system in combination with fluorescence derivatization has been developed for the highly sensitive and selective analysis of chiral amino acids in extraterrestrial samples . As the targets alanine 2 aminobutyric acid valine norvaline and isovaline frequently found chiral amino acids in the carbonaceous chondrites were selected . These amino acids were pre column derivatized with 4 fluoro 7 nitro 2 1 3 benzoxadiazole and the target analytes were separated from other amino acids and organic compounds by a reversed phase column in the first dimension . The targets were further separated from interferences by an anion exchange column in the second dimension and their enantiomers were separated and determined in the third dimension by a Pirkle type enantioselective column . The present 3D HPLC system was validated and applied to the Murchison meteorite and the Antarctic meteorites and all of the target amino acid enantiomers were clearly observed without severe interferences . The L values of the non proteinogenic amino acids were almost 50 in both meteorites and even the proteinogenic amino acids were almost racemic in the Antarctic meteorites .
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A 3D HPLC system was developed for the determination of chiral amino acids. Enantiomers of Ala 2AB Val nVal and iVal were determined. All 5 target amino acids were clearly determined in carbonaceous chondrites. Non proteinogenic amino acids are almost racemic in Murchison Antarctic meteorites.
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S0021967320305355
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Fixed dose combination of tenofovir disoproxil fumarate and lamivudine is one of the most preferred FDC for the treatment of acquired immunodeficiency syndrome human immunodeficiency virus infection . To the best of authors knowledge there are no reported methods for chiral purity estimation of both drugs simultaneously from a FDC . The current study was focused on the development of a single chiral method uisng supercritical fluid chromatography for separation of stereoisomers of TDF and 3TC combination employing design of experiment approach . Method development was planned in three steps by using different experimental designs for each step . I optimal Taguchi orthogonal array and face centred central composite designs were employed for primary parameter selection secondary parameter screening and final method optimization respectively . All six stereoisomers were separated in a 10 minute run on Chiralpak IA column with carbon di oxide methanol as mobile phase at 1.5 mL min in gradient mode . The optimized method was verified for performance through establishing specificity precision linearity accuracy limit of quantification and solution stability . Resolution between each isomeric pair was more than 1.5 . The method was found to be linear from 1.5 g mL to 7.5 g mL for 3TC and 7.5 g mL to 37.5 g mL for TDF stereoisomers . The R
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chiral method for separation of. of TDF and 3TCin FDC. Use of UHPSFC with sub 2 micron particle size column for time efficient separation. 3 Step DoE strategy selection screening and optimization for method development. Use of I optimal Taguchi OA and CCD experimental designs to evaluate CMPs. Final optimized method well aligned with regulatory requirements for quantification.
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S0021967320305379
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An analytical procedure for the rapid and selective derivatization of free fatty acids into methyl esters directly in plasma without transmethylation of lipid bound fatty acids was developed for their analysis by gas chromatography mass spectrometry . The methyl esters of free fatty acids were obtained by reaction with methyl iodide in the solution of dipolar aprotic solvents and in the presence of solid bases . The mechanism of the methylation reaction with these reagents was investigated . Optimal conditions for the selective methylation of free fatty acids were established using different dipolar aprotic solvents and different solid bases . The possible transmethylation of covalently bonded fatty acids from plasma lipids has been investigated under different experimental conditions in order to be avoided . Total methylation of free fatty acids was achieved in 1 min at room temperature using methyl iodide and anhydrous potassium carbonate or sodium carbonate in dimethyl sulfoxide . Under these conditions transmethylation of lipid bound fatty acids was avoided . The methyl esters can be injected directly from the reaction solvents . A plasma volume of 50 L was used without special purification . The detection limits were around 0.1 ng L. The proposed method avoids the drawbacks of the previous methods used for the one step analysis of individual free fatty acids in human plasma .
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Direct and selective methylation of plasma free fatty acids for GC. Complete methyl esterification in 1 min at room temperature. Avoid transmethylation of lipid bound fatty acids. Direct injection from derivatization solvents. No supplementary sample preparation.
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S0021967320305380
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Complexation between poly and borax in aqueous solution yields a dynamic polyelectrolyte . Study of chain conformation of such a polyelectrolyte is challenging due to the difficulty in separating different macromolecular species . In this study we investigated conformation of dilute PVA chains complexed with borax in a wide concentration range between 0.02 and 78.6 mM using asymmetrical flow field flow fractionation . We find that elution of the complexes is strongly influenced by the borax concentration owing to the charged complex is repelled electrostatically by the charged bottom membrane of the AF4 channel and the Debye screening length reduces with increasing a charge density . The chain conformation of PVA borax complexes depends on both polymer molar mass and borax concentration . At low borax concentrations of 0.02 0.5 mM a transition from random coil to rod like conformation is observed with increasing the chain size . At borax concentrations of 1 mM and higher all chains become random coil owing to a reduced screening length of the electrostatic repulsion .
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AF4 separation of PVA borax complex is influenced by borax concentration in eluent. Retention of the complex is altered by electrostatic repulsion with the membrane. A coil to rod transition is observed for the complexes at low borax concentrations. All complexes become solely random coil at sufficiently high borax concentrations
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S0021967320305392
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The high cost of protein A resins drives the biopharmaceutical industry to maximize its lifetime which is limited by several processes usually referred to as resin aging . In this work two model based strategies are presented aiming to control and improve the resin lifetime . The first approach purely statistical enables qualitative monitoring of the column state and prediction of column performance indicators from chromatographic on line data . The second one referred to as hybrid modeling is based on a lumped kinetic model which includes two aging parameters fitted on several resin cycling experimental campaigns with varying cleaning procedures . The first aging parameter accounts for binding capacity deterioration while the second accounts for a decreased mass transfer rate . The hybrid model provides important insights into the prevailing aging mechanism as a function of the different CPs . In addition it can be applied to model based CP optimization and yield forecasting with the capability of state estimation corrections based on on line process information . Both approaches show promising results which could help to significantly extend the resin lifetime . This comes along with increased understanding reduced experimental effort decreased cost of goods and improved process robustness .
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Five different column lifetime experimental data sets with altered cleaning harshness. Two model approaches to describe resin aging understand aging mechanisms and optimize cleaning. Statistical approach enables estimation of column quality yield DBC and impurities. Elaboration of a hybrid approach based on a lumped kinetic model extended with two aging parameters. Hybrid approach exhibits increased extrapolation forecast and on line update capability.
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S0021967320305409
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In this paper a semi analytical investigation was performed to study the effect of the geometrical parameters of insulator based dielectrophoresis systems for cell free DNA trapping . For this purpose first electrical potential and fluid flow fields were calculated by solving the governing equations including Poisson and Navier stokes equations with appropriate boundary conditions and then a Lagrangian approach was utilized to analyze the motion of cfDNA under the most important forces affected on it including Brownian Drag electrophoresis and dielectrophoresis forces . The effect of the different parameters such as the electrical conductivity of the medium shape and geometrical parameters of the insulators on the dielectrophoretic behavior of cfDNA was studied and the optimal value of these parameters was presented . Finally in order to predict the minimum voltage required for cfDNA trapping artificial neural network was utilized and a relation between input and output parameters was introduced .
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DEP can be used to rapidly detect and separate cfDNA. Effect of the geometrical parameters of the insulators on cfDNA trapping is studied. High solution conductivity increases the applied voltage for cfDNA trapping. ANN is used for the prediction of the minimum voltage required for cfDNA trapping.
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S0021967320305434
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Column miniaturization of liquid chromatography is a major trend in separation sciences with the advent of single cell proteomics and metabolomics . Nanochannel chromatography is one of the promising tools for single cell analyses because it provides ultra small sample volume and high separation efficiency . However non fluorescent molecular detection in such small channels is still quite difficult due to fLaL sample volume which hinders further miniaturization of nanochannels . In this study we overcame the size limitation of nanochannel chromatography by our label free molecular detection method photothermal optical diffraction which utilizes the photothermal effect of analytes and optical diffraction by nanochannel . The combination of the nanochannel chromatography and the POD enables 1.8 fL sample separation and label free molecule detection in nanochannels with 800 nm width and 300 nm depth at the optimized experimental conditions . The limit of detection is 5.4 zmol approximately 50 times lower than the conventional label free detection method . Furthermore the theoretical plate number is calculated to be 10
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Photothermal optical diffraction is a label free molecule detection method for nanochannels. Femtoliter normal phase chromatographic separation was realized in10. nm channel. Separated samples were detected by photothermal optical diffraction with LOD of 5.4 zeptomol. Nanochannel chromatography showed high theoretical plate number 10. plates m .
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S0021967320305446
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The search for biomarkers allowing the assessment of disease by early diagnosis is facilitated by liquid chromatography . However it is not clear how many components are lost due to being present in concentrations below the detection limit and or being obscured by chromatographic peak overlap .
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Chromatographic signal simulations investigate peaks near the limit of detection. Low level peaks are obscured by peak overlap not the limit of detection. Alternatives to the Enke Nagels log normal distribution of signals are investigated
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S0021967320305458
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We describe the design and performance evaluation of a portable gas chromatograph suitable for the analysis of volatile organic and odorous compounds at trace levels . The system comprises a carbon nanotube sponge preconcentrator an electronic pressure control unit a temperature programmable column module and a fast response photoionization detector . A built in tablet computer controls instrumental parameters and chromatogram display functions . The compact GC with dimensions of 35 cm 26 cm 15 cm is self contained weighing less than 5 kg without a battery pack and uses no auxiliary compressed gases . Our design has three main advantages over conventional portable GCs recharging configuration of ambient air as the carrier gas using a miniature diaphragm pump precise control of column flow by the built in canister and EPC system and rapid thermal desorption of the preconcentrator facilitated by intrinsic resistivity of the carbon nanotube sponge . A 30 m 0.28 mm I.D . capillary column operated at a head pressure of 14 psi provided a peak capacity of 55 for a 10 min isothermal analysis . The temperature programmability feature could decrease the analysis time of less than 5 min for vapor mixture of benzene toluene ethylbenzene and
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GC analysis 10 min of volatile organics at sub ppb levels was done. Electronic pressure control facilitated use of compressed ambient air as carrier gas. Temperature programming was achieved by the at column heater and insulation module. Photoionization detector exhibited a fast response 90 ms. Sensitivity was increased 100 fold using a carbon nanotube sponge preconcentrator
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S0021967320305471
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Fluorous affinity means remarkably specific interaction between highly organic fluorides . This work aims to explore the potential of fluoro functionalized stationary phase for the separation of organic fluorides by means of fluorous fluorous interaction . Here by using the Michael addition strategy between 1H 1H 2H 2H perfluorodecanethiol and polydopamine a novel fluoro functionalized stationary phase was synthesized for open tubular capillary electrochromatography . The
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Fluoro functionalized stationary phases for capillary electrochromatography. Michael addition and polydopamine functionalization for stationary phase preparation. The F column has excellent separation performance for neutral and fluorinated compounds. The column has good reproducibility and stability
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S0021967320305483
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In sample pre treatment millifluidic electromembrane platforms have been developed to extract and pre concentrate target molecules with good clean up that minimize matrix effects . Optimal operation conditions are normally determined experimentally repeating the extractions at different conditions and determining the efficiencies by an analytical technique . To shorten and simplify the optimization protocol millifluidic platforms have been electrically characterized by impedance spectroscopy . The magnitude of the resistance of the electromembrane has been found very predictive of the migration capacity and extraction efficiency of three different parabens on real time . The optimal conditions have been successfully applied in the extraction of parabens from urine samples that not only improves the extraction efficiency but also provides a very low current intensity which is very important in electromembrane to minimize electrolysis phenomena . The possibility to optimize one of the most critical and important parameters such as the voltage with a simple electrical model may accelerate the production of application specific millifluidic electromembrane platforms in a short development time . The results showed that millifluidic electromembrane extraction based low voltage has a future potential as a simple selective and time efficient sample preparation technique allowing a simple battery as power supply .
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An impedance model allows to optimize electrical conditions in electromembrane. Parabens are extracted via electromembrane into a chip with efficiencies of 100 . The procedure is succesfully applied in urine samples with high recoveries. The electrical characterization of the circuit in millifluidic systems is proposed.
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S0021967320305495
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Per and polyfluoroalkyl substances are ubiquitous in the environment . However only a limited number of predominantly persistent perfluoroalkyl acids have been analyzed in edible plants so far . We present a generic trace analytical method that allows for quantification of 16 intermediate fluorotelomer alcohol or perfluoroalkane sulfonamidoethanol based transformation products as well as 18 PFAAs in plants . Additionally 36 suspected intermediate PFAS transformation products were qualitatively analyzed . The ultrasound assisted solid liquid extraction of wheat and maize grain maize leaves Jerusalem artichoke and ryegrass was followed by a clean up with dispersive solid phase extraction using graphitized carbon adsorbent and chemical analysis by reversed phase liquid chromatography tandem mass spectrometry . The method was based on matrix matched and extracted calibration and displayed good precision with relative standard deviations in triplicate analyses typically below 15 for all quantified analytes and matrices . An average deviation of 12 between quantified concentrations obtained by matrix matched and extracted calibration and a method based on isotopically labelled internal standards underlines the good trueness of the method . The method quantification limits for the majority of analytes in all plant samples were in the low ng kg concentration range on a dry weight basis . Plant matrices were analyzed from crops grown on agricultural fields that have been contaminated with PFASs . FTOH and or FASE based intermediate transformation products were detected in all samples with
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A trace analytical method for PFAS transformation products in plants was developed. A total of 70 PFASs were analyzed quantitatively 34 or qualitatively 36 . Method validation displayed good accuracy of quantification. Plant samples from contaminated fields contained intermediate transformation products. Leafy parts of the plants showed the highest contamination.
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S0021967320305501
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Trapping multiple dual mode is a preparative liquid liquid chromatography technique well suited to difficult separations of intermediately eluting components from similarly structured impurities . In this demonstrative study a design approach for high process throughput is applied for the trapping MDM separation of a target component nootkatone initially comprising 16.7 of an industrial side stream mixture with over 90 impurities . This design approach previously developed and validated using ternary mixtures of model solutes is applied to a complex real mixture for the first time . The approach consists of five steps determination of the maximum starting mixture concentration for feed preparation determination of the maximum flow rate for maintenance of the pre set stationary phase fraction determination of the partition coefficients of the target and main impurities selection of step durations and number of cycles using an established short cut method execution of the trapping MDM separation . The target NK was obtained along with a co eluting component at 78.7 purity and 84.6 yield demonstrating the effectiveness of trapping MDM for the separation of intermediately eluting natural product target components from complex starting mixtures .
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Liquid liquid chromatography separation of an intermediately eluting component. 5 step design approach applied to a complex natural product starting mixture. Use of short cut method for selection of trapping MDM step durations. Target separation from 90 impurities at 79 purity and 85 yield.
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S0021967320305513
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The description of the profiles of chromatographic peaks has been studied extensively with a large number of proposed mathematical functions . Among them the accuracy achieved with modified Gaussian models that describe the deviation of an ideal Gaussian peak as a change in the peak variance or standard deviation over time has been highlighted . These models are in fact a family of functions of different complexity with great flexibility to adjust chromatographic peaks over a wide range of asymmetries and shapes . However an uncontrolled behaviour of the signal may occur outside the region being fitted forcing the use of different strategies to overcome this problem . In this work the performance of the LMG PVMG and PLMG models is compared with variants obtained by combination of the modified Gaussian models with an equation that adds an exponential tail and with other functions that limit the growth of the independent variable . The behaviour of the approaches is checked through the simultaneous fitting of enantiomeric peaks showing a wide range of characteristics obtained in the separation of drugs with chiral activity by liquid chromatography using enantioselective columns . The study is also carried out with the purpose of performing the deconvolution of the peaks of the enantiomers when these are not completely resolved in order to evaluate the enantiomeric fraction .
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Modified Gaussian models were applied to fit peaks of enantiomeric compounds. Restrictions were applied to control the baseline out of the peak region. Peak models allowed excellent fitting of isolated symmetric and asymmetric peaks. Deconvolution of peaks with moderate overlapping was also satisfactory. Approaches were applied to eight drugs analysed with several chiral columns
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S0021967320305525
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An ultra high performance liquid chromatography quadrupole time of flight mass spectrometry method was employed for chemical identification in a commercial polyvinyl chloride polyethylene multilayer film . Over 30 chemicals from different layers of the film were identified and were classified into 6 groups including antioxidants plasticizers slip agents antistatic agents adhesive components etc . Special attention was placed on the analysis of some non intentionally added substances and oligomers in adhesive . Based on the identification results six additives were selected and their migration behaviors were investigated via one sided contact migration test . The migration test was performed by exposing the PE side of the film to different simulating solutions at 40C as well as recording the migration level as a function of time . No obvious migration was found into water for all additives while the migration into 40 and 95 ethanol followed Fickian diffusion behavior and could be described by Fick s diffusion equation . Diffusion coefficients derived from the equation were in a range of 10
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Identification of chemicals in a commercial PVC PE film was performed by UPLC QTOF MS. Special attention was placed on the analysis of non intentionally added substances NIAS. Six chemicals additives were selected and investigated on migration behaviors. Parameters associated with the migration process were derived from Fick s diffusion equation
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S0021967320305537
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Efficient extraction of polar sulfonamides antibiotics from aqueous samples and food is very challenging because they are hydrophilic their concentration is very low and the matrix is complex . Covalent organic frameworks a novel porous organic material have attracted great attention . In this work the spherical triphenylbenzene dimethoxyterephthaldehyde COFs were synthesized by a simple room temperature method and due to their attractive properties such as high outstanding acid base stability large specific surface area low skeletal density inherent porosity and high crystallinity so TPB DMTP COFs as ideal solid phase extraction adsorbents showed excellent adsorption performance for trace polar sulfonamides in food and water . TPB DMTP COFs were characterized by scanning electron microscopy Fourier transform infrared spectroscopy powder X ray diffraction and so on . The important parameters were optimized to improve the extraction efficiency of TPB DMTP COFs toward sulfonamides . Analysis of sulfonamides was performed by liquid chromatographytandem mass spectrometry . The developed method based on TPB DMTP COFs material achieved low limits of detection 0.51.0 ng L
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Spherical TPB DMTP COFs was used as a SPE material for the first time. The material achieved low LODs and good repeatability for sulfonamides. It was used for the enrichment and analysis of sulfonamides in real samples.
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S0021967320305549
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The monodisperse pillararene based polymeric sub microsphere was prepared by polycondensation of hydroxylated pillararene and cyanuric chloride through a one pot reaction in mild condition . The preparation was realized by a simple two step temperature programmed process without heating operation . The obtained polymeric sub microsphere exhibited monodisperse and regular spherical structure with uniform particle size distribution of 220320nm accounting for 94 . The prominent adsorption capacity of the polymeric sub microsphere for antioxidants was demonstrated and attributed to the synergistic effect of the cladding interaction with the electron rich cavity and hydrophilic interaction with terminal hydroxyl on pillararene . Then the pillararene sub microsphere was packed into a micro column to realize effective on line enrichment of antioxidants coupling with high performance liquid chromatography . The flow rate of extraction and desorption solvent clean up and desorption volume were assessed to optimize the method . The method showed wide linear ranges with
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Novel pillar 5 arene based sub microsphere was fabricated in mild condition. The polymer shows regular spherical structure and good monodispersity. On line SPE coupled with HPLC for determination of antioxidants was established. Successful application to the migration of food contact materials.
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S0021967320305550
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The influence of impregnation the chromatographic plate adsorbent layer silica with hen s egg white albumin or bovine serum albumin on the retention of some popular medicines is investigated . The effect of composition and buffer pH of the mobile phase on solute separation selectivity is also studied . The chromatographic systems with and without above mentioned albumins and their influence on investigated drug retention are compared . In general it has been turned out that retention of tested medicines in systems with the sorbent impregnated with albumin significantly increase relative to those with non impregnated .
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A new method of impregnating the adsorbent layer of a chromatographic plate with hen s egg white albumin or bovine serum albumin. Influence of albumin modified adsorbent layer on the retention of different analytes in TLC systems. Solvent front position extraction SFPE .
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S0021967320305562
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A fast non invasive high performance liquid chromatographic screening method with electrospray ionization mass spectrometric detection was developed for the analysis of three major glycine conjugated bile acids in human saliva . Using a mobile phase composed of 80 methanol and 0.1 formic acid glycocholic glycodeoxycholic and glycochenodeoxycholic acids were separated in less than 4 minutes with sensitivity in the low nM range . Bile acids are thought to contribute to the pathology of various complications in gastroesophageal reflux disease for instance Barrett s esophagus which may eventually lead to esophageal carcinoma . In this pilot study samples of saliva obtained from 15 patients with Barrett s esophagus of various severities were compared to saliva samples from 10 healthy volunteers . Glycochenodeoxycholic acid was significantly elevated in the patients and principal component analysis of all bile acids could distinguish the most severe Barrett s esophagus patients . We also reported on the detection of glycochenodeoxycholic acid in exhaled breath condensate for the first time . The promising results of this pilot study warrant future investigation aiming at non invasive diagnostics of Barrett s esophagus susceptibility in patients with gastroesophageal reflux disease .
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Fast non invasive HPLC MS method for bile acids analysis in saliva was developed. Saliva from patients with Barret s esophagus and healthy controls was obtained. Glycochenodeoxycholic acid is a promising biomarker for Barret s esophagus diagnostics. PCA could distinguish the patients with most severe Barret s esophagus condition
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S0021967320305574
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We report on a comparative study of the basic separation kinetics of commercial packed bed columns and a micro pillar array column working in the 1 10L min flow rate range i.e . operating in the area of capillary flow LC . This is done using a basic test mixture of 8 alkylphenones under both isocratic and gradient separation conditions . Care was taken the PAC and the packed bed columns have similar volumes and hence also similar t
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A micro pillar array column operating in the capillary flow rate range is introduced. Performance is compared to three state of the art capillary LC packed bed columns. Isocratic efficiency and gradient peak capacity are compared in 1 10L min range. Fixed length kinetic plot emphasizes difference in dynamic efficiency range.
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S0021967320305586
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Polysaccharide based chiral stationary phases are outstandingly suitable to play a key role in chiral HPLC method selection strategies since they provide high success rates . One reason for this ability is that they adopt a diversity of higher order structures in various eluents resulting in versatile chiral environments .
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Polar organic mode chiral screening sequence was designed with a novel approach. Methods using alcohol ratios resulting in history dependent retentions were included. The multiple states of the selector can address needs of pharmaceutical analysis. The proposed strategy combines versatility with practical simplicity.
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S0021967320305598
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Polysaccharide based chiral stationary phases are the most used chiral selectors in HPLC . These CSPs can be used in normal polar organic and aqueous organic mobile phases . However normal and polar organic mobile phases are not adequate for chiral separation of polar compounds for the analysis of aqueous samples and for MS detection . In these situations reversed phase conditions without the usual non volatile additives incompatible with MS detection are preferable . Moreover in most of the reported chiral chromatographic methods retention is too large for routine work . In this paper the chiral separation of 53 structurally unrelated compounds is studied using three commercial amylose based CSPs coated amylose tris
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Compared enantioresolution Rs in 3 amylose based chiral stationary phases CSPs. Rs discriminant models of 2 Amylose CSPs in RPLC after feature selection. Rs topological molecular descriptor relationships for unrelated compounds. Chiral carbon topological parameters are key variables for enantioresolution. Aromatic and nitrogen related parameters connect with enantioresolution
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S0021967320305604
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In recent years coreshell silica particles have been increasingly used for highly efficient separation at fast flow rates and relatively low back pressures in high performance liquid chromatography . However material synthesis techniques for producing CSSPs economically in batch processes remain elusive . In this report a practical and straightforward method for the preparation of CSSPs is presented . By refluxing freshly prepared nonporous silica particles in ammoniawater solution in the presence of poly at 70100C CSSPs with shell thicknesses of up to 300 nm and pore sizes from 8 to 25 nm were easily prepared . The effects of the synthetic conditions on the shell thickness surface area and pore size were investigated in detail and the method reproducibility was evaluated in scale up experiments . A mechanism of CSSP formation is also proposed . The CSSPs were characterized via scanning electron microscopy transmission electron microscopy laser particle size analysis and nitrogen adsorption and desorption experiments . The synthesized 3.4 m CSSPs were functionalized with dimethyloctadecylchlorosilane and used as an HPLC packing material exhibiting excellent separation performance for both small molecules and large biomolecules . In summary we report the simplest method developed thus far for the preparation of monodisperse coreshell silica particles suitable for HPLC column packing .
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Monodisperse coreshell silica particles are formed by continuous self assembly. The in situ silica sol gel method can be easily scaled up for production. Excellent column performance for HPLC separation.
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S0021967320305616
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Two dimensional liquid chromatography is increasingly being used to address challenging separations in fields ranging from pharmaceutical analysis to the food industry . A significant impediment to development of more methods is the lack of a complete theoretical foundation upon which sound development decisions can be made . One parameter that is currently not fully understood is the extent of filling of sampling loops in the case where effluent from the first dimension separation is transferred to the second dimension separation through this type of open loop interface . This is a highly important parameter because it is connected to several other variables in a 2D LC system including the first dimension flow rate the sampling time and the loop volume . In this study we have used both numerical simulation methods and experimental measurements to understand the extent to which sampling loops can be filled before a significant fraction of the analyte is lost from the end of the loop . Variables included in the study are the analyte diffusion coefficient D
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Sample breakthrough from modulation loops used for 2D LC was simulated. Universal breakthrough curves were found that only depend on a dimensionless t factor. The maximum loop filling for a given level of analyte loss was determined as a function of t . Very good agreement was found between experimental and simulation results for straight loop capillaries. Coiling of the loop capillary enhances radial mixing suppresses analyte loss.
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S002196732030563X
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An experimental methodology for the determination of the obstruction factor in the expression for mesopore diffusion in Zorbax Eclipse Plus C
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Experimental protocol for determination of mesopore diffusion obstruction factor. Parallel column set up proposed for peak parking of unretained compounds. Deuterated solvent molecules used as tracer molecules in same solvent mobile phase. Experimental data suggest that pore geometry reflects monolithic like structure
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S0021967320305641
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In the past two decades supercritical fluid chromatography has evolved from a niche application to a comprehensive technology and a fully fledged alternative to conventional high performance liquid chromatography .
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Chiral separation of synthetic cathinones on zwitterionic column is achieved. Gradient elution of analytes is superior to isocratic elution conditions. Gradual reduction of a make up solvent added post column enhances signal intensity.
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S0021967320305720
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It is significant to precisely isolate potential active compounds from medicinal herbs containing multiple compounds . Herein a new strategy for precise separation of lysine specific demethylase 1 inhibitors from the rhizome of
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A new strategy for precise separation of lysine specific demethylase 1 inhibitors. Multi mode CCC separation guided by molecular docking and LC MS MS analysis. The PH zone refining and recycling CCC separation finished by only one instrument. Compound. showed the potential ability of prohibiting tumor invasion and metastasis
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S0021967320305732
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In addition to the diverse extraction techniques available capsule phase microextraction which uses a microextraction capsule has recently been introduced as a sorptive based sample preparation technique . In this study two different MECs MEC
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Development of novel sol gel mixed mode MECs. Evaluation of mixed mode ion exchange MECs by CPME. Highly selective extraction of acidic or basic analytes. Satisfactory recoveries from optimized CPME parameters. Successful application in the extraction of ionizable compounds from environmental samples.
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S0021967320305744
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Saponins constitute an important class of secondary metabolites of the plant kingdom . Here we present a mass spectrometry based database for rapid and easy identification of saponins henceforth referred to as saponin mass spectrometry database . With a total of 4196 saponins 214 of which were obtained from commercial sources . Through liquid chromatography tandem high resolution mass spectrometry analysis under negative ion mode the fragmentation behavior for all parent fragment ions almost conformed to successive losses of sugar moieties dissociation and McLafferty rearrangement of aglycones in high energy collision induced dissociation . The saccharide moieties produced sugar fragment ions from
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We established a mass spectrometry database SMSD with 4196 saponins data. SMSD is freely accessible at http 47.92.73.208 8082 or http cpu smsd.com. SMSD provides CLASSIFY SEARCH and METABOLITE functions. Mass defect and logistic regression model are applied for CLASSIFY and SEARCH.
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S0021967320305756
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In this study superficially porous silica particles with a nominal pore size of 450 and average particle size of 2.6 micrometers was compared to fully porous silica particles with nominal particle size 3 micrometers and nominal pore size 1000 A as carriers for a polysaccharide based chiral selector for the separation of enantiomers in high performance liquid chromatography . In addition the effects of chiral selector loading onto the silica support and of column internal dimeter in the case of both superficially porous and totally porous silica as well as of the pore size of superficially porous silica on column performance were studied . The dependence of plate height on mobile phase flow rate was also studied and attempts were made for shortening analysis time . The baseline separation of enantiomers of some chiral sulfoxides was obtained within 2.04.5s .
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Comparison of fully and superficially porous polysaccharide based chiral stationary phases. Effect of chiral selector loading and column internal diameter on performance. Baseline separation of enantiomers in few seconds.
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S0021967320305768
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This study has examined the batch binding behaviour of different thermo responsive co polymer grafted chromatographic materials under different temperature and protein loading conditions . The effect of molecular composition of poly
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16 Novel temperature responsive copolymers synthesised by free radical polymerisation. Impact of monomer composition on phase transition properties of these SRP documented. Composition specific lower critical solution temperature LCST attributes determined. 6 SRP co polymers of different compositions immobilised onto cross linked agarose. Unique protein adsorption properties measured with these new SRP chromatographic sorbents.
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S0021967320305781
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Multi column continuous chromatography has advantages of high resin capacity utilization and productivity low buffer consumption and small footprint . Experimental optimization is often time consuming and inefficient due to the complexity of continuous processes . In this study a model based approach was investigated to improve process development of twin column continuous capture with Protein A affinity resin MabSelect PrismA . Breakthrough curves under various conditions productivity and capacity utilization
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A model based approach was used for continuous capture process development. Twin column continuous capture with MabSelect PrismA affinity resin was focused. Interactive effects of parameters were studied with process performance profiles. Contour maps were used to optimize the working window for continuous capture. Model based predictive operating conditions were verified by experiments.
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S0021967320305793
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In this work we utilized basic and acidic analytes to investigate the ionic interaction participation in retention behavior of selected reversed phase and polar columns . The test analytes included nitrate benzenesulfonate and trimethylphenylammonium ions . The fully aqueous mobile phase comprising 10mM dichloroacetic acid buffered with ammonia solution to desirable pH was used for retention experiments . Developed method was utilized to study the ionic interactions of stationary phases in pH range between 2.5 and 9.0 . We demonstrate that selected sorbents used for reversed phase and hydrophilic interaction chromatography separations exhibit cation or anion exchange interactions . We compare the results to novel Atlantis PREMIER BEH C18 AX mixed mode column that combines reversed phase and anion exchange interaction modes . We evaluated the relative retention strength of selected columns for anionic and cationic analytes .
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We propose method for evaluation of ionic interactions of liquid chromatography. Permanently ionized organic and inorganic ions were utilized as test analytes. Aqueous ammonium dichloroacetate mobile phases are used in range pH 2.59.0. The method is applicable for characterization of mixed mode columns.
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S002196732030580X
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Additives are added to polymers in small concentration to achieve desired application properties widely used to tailor the properties . The rapid diversification of their molecular structures with often only minute differences necessitates the development of adequate chromatographic techniques . While modified silica so far is the workhorse as stationary phase we have probed the potential of porous graphitic carbon Hypercarb
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Porous graphitic carbon Hypercarb. enables LC separation of polymer stabilizers. Raman spectroscopy exhibits shifts of the graphite band caused by adsorption. Argon physisorption provides proof for adsorption of polymer additives. Adsorption reduces the specific surface area of Hypercarb
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S0021967320305811
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The chromatographic performances of four coated and immobilized amylose phenylcarbamate based chiral columns were evaluated and compared under normal phase elution conditions by using chiral 4 4 bipyridine derivatives as analytes .
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Enantioseparation of 3 3 5 5 tetrachloro 2 iodo 2 substituted 4 4 bipyridines. Comparative enantioseparations on coated and immobilized amylose based selectors. Effect of introducing methanol in the mobile phase is described. Temperature dependent enantiomer elution order reversal was observed.
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S0021967320305823
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A twin column Multicolumn Countercurrent Solvent Gradient Purification process has been developed for the purification of a therapeutic peptide glucagon from a crude synthetic mixture . This semi continuous process uses two identical columns operating either in interconnected or in batch mode thus enabling the internal recycle of the portions of the eluting stream which do not comply with purity specifications . Because of this feature which actually results in the simulated countercurrent movement of the stationary phase with respect to the mobile one the yield purity trade off typical of traditional batch preparative chromatography can be alleviated . Moreover the purification process can be completely automatized .
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A MCSGP process has been developed for the purification of glucagon from a crude synthetic mixture. The procedure on how to develop the MCSGP process from a single batch experiment is illustrated. MCSGP allowed a 23 increase in yield with respect of single column process at a constant purity.
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S0021967320305847
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A pentafluorobenzoylation liquid chromatography tandem mass spectrometry method was developed for qualitative and quantitative analysis of ethanolamines . With this method highly hydrophilic EAs can be sufficiently analyzed with a commonly used reversed phase column
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Proposal of a new analytical procedure for degradation products of nitrogen mustards. LC MS MS analysis after derivatization with pentafluorobenzoyl chloride. Sufficient chromatographic behavior with reversed phase column. Evaluation of applicability based on recovery tests from biological samples.
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S0021967320305860
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The Wayne State University experimental descriptor database is utilized to bench mark the current capability of the solvation parameter model for use as a quantitative structure retention relationship tool for estimating retention in gas and reversed phase liquid chromatography . The prediction error for the retention factors of varied compounds on six open tubular columns for gas chromatography and three packed columns for reversed phase liquid chromatography SunFire C
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Retention prediction error bench marked for the solvation parameter model in GC and RPLC. Average absolute error for retention factor predictions in GC 0.1 to 0.4. Average absolute error for retention factor predictions in RPLC 0.3 to 0.5. Descriptor quality for WSU compound descriptor database verified. Retention mechanism heterogeneity is the main source of prediction errors
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S0021967320305872
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The adsorption behavior of the model proteins alpha Lactalbumin Bovine Serum Albumin Lysozyme and a monoclonal antibody in single component and in binary mixtures was investigated on two different hydrophobic interaction chromatography resins using both static and dynamic methods . A kinetic model of the adsorption process was developed which accounted for protein unfolding and intermolecular interactions in the adsorbed phase . The latter incorporated positive cooperative interactions resulting from preferred and multilayer adsorption on the adsorbent surface as well as negative cooperative interactions attributed to exclusion effects due to size exclusion and repulsion . Cooperative adsorption resulted in negative or positive deviations from the Langmuir model for both single and multicomponent isotherms . The model was used to assess possible contributions of different adsorption mechanisms of proteins and their structurally different forms to the overall adsorption pattern as well as to simulate chromatographic band profiles under different loading conditions .
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Single and competitive adsorption isotherms of proteins were measured on HIC media. A kinetic model of protein adsorption was developed to describe protein adsorption behavior. The model accounted for protein unfolding positive and negative cooperative adsorption. The approach for correlation of static and dynamic binding of proteins in HIC was developed.
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S0021967320305896
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Comprehensive two dimensional gas chromatography is a powerful tool for complex separations . The selectivity and sensitivity benefits from thermally modulated GCGC were applied to the analysis of polychlorinated dibenzo
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Rxi 17SilMS crossed with Rtx Dioxin2 can be used for dioxin analysis in GCGC. All 17 toxic dioxins are separated from each other in a single separation. 11 toxic dioxins are fully resolved from interfering dioxin congeners. Successful GCGC modeling of 40 dioxin congeners.
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S0021967320305975
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The aim of this study is to model describe and predict the mass transfer of IgG as a function of the agarose concentration in the protein A stationary phase taking into account the influence of adsorption on the pore size . Therefore particle size distribution bed and bead porosities were examined by light microscopy pressure flow behavior and iSEC . Three agarose protein A stationary phases were investigated . The pore size decreased from 116nm for 2wt to 54nm for 6wt and the porosity for the target molecule IgG was reduced by 25 . A shrinking core model approach was used to assess the influence of IgG adsorption on the pore size of the stationary phase and the diffusivity of IgG . Due to IgG adsorption the pore diameter reduced by 24nm which is approximately two times its hydrodynamic diameter . Effective pore diffusivities of IgG were obtained by fitting the general rate model to breakthrough curves . They were in the range between 3.96
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Adsorption in affinity chromatography stationary phases reduces the pore diameter. Accessibility and effective pore diffusion are depending on the pore diameter. Diffusivity is obtained by fitting the general rate model to breakthrough curves. A modified Ogston model describes pore diameter dependent diffusion coefficient.
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S0021967320305987
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BMS 986142 is a Bruton s tyrosine kinase inhibitor under development to treat several disease types . The compound contains three chiral elements one chiral center and two chiral axes resulting in three potential atropisomeric impurities in its drug substance and drug products . Separation of BMS 986142 atropisomers has been successfully achieved on an achiral polar embedded C18 column in reversed phase liquid chromatography and on polysaccharide based chiral columns in RPLC and supercritical fluid chromatography . Compared to the RPLC chiral separation the SFC atropisomeric separation on a sub 2 m immobilized cellulose based column is much more efficient and environmentally friendly . The analysis time in SFC was reduced by 8 fold compared to that in RPLC and the method sensitivity in SFC on the sub 2 m chiral column in 3.0mm I.D . was 2 to 4 fold better than that on 3 m chiral columns in 4.6mm I.D .. Furthermore our study suggests that the contribution to band broadening from the extra column volume of modern commercial SFC instrument was not negligible for a 3.0mm I.D.100mm column packed with 1.6 m particles . This result reaffirms that there is a great need for further improvement of SFC instrument design in order to realize the full theoretical efficiency of both sub 2 m achiral and chiral columns .
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Successful separation of four atropisomers of Bruton s tyrosine kinase inhibitor BMS 986142 achieved on achiral and chiral columns in HPLC and on chiral column packed with sub 2 m in SFC. Excellent diastereomeric selectivity towards BMS 986142 atropisomers afforded by cellulose based chiral stationary phases in general. Better efficiency productivity and sensitivity demonstrated by the separation on sub 2 m IB U column in 3.0mm I.D. when compared to the same type columns in 4.6mm I.D. in SFC. Inadequacy of modern SFC instrument for column packed with 1.6 m particles in 3.0mm I.D.100mm dimension revealed by kinetic performance analysis with compound BMS 986142.
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S0021967320306014
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An overarching theory of chromatography capable of modeling all analyte stationary phase interactions would enable predictive design of pharmaceutically relevant separations . The stochastic theory of chromatography has been postulated as a suitable basis to achieve this goal . Here we implement Dondi and Cavazzini s Monte Carlo framework that utilizes experimentally accessible single molecule kinetics and use it to correlate heterogenous adsorption statistics at the stationary phase to shifts in asymmetry . The contributions can not be captured or modeled through ensemble chemometrics . Simulations reveal that peak asymmetry scales non linearly with longer analyte stationary phase interactions and migrates towards symmetry across the column length even without column overloading .
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The asymmetry factor fails to correlate with mixed mode adsorption and analyte loss. Monte Carlo simulations illustrate when chemometrics correlate to surface chemistry. Stochastic theory simulations provide new ways to design stationary phases. Kinetic tailing reduces analyte recovery when the ratio of desorption times is 100.
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S0021967320306026
|
Sorption of PFASs onto surfaces of laboratory materials has been frequently reported . Due to the often complex and poorly understood nature of such sorption workarounds have often included use of whole samples only accompanied by sample vessel rinsing to desorb active surfaces . The resulting methods tend to require considerable sample preparation times and preclude typical activities such as aliquoting and dilution of water samples prior to extraction . This manuscript reports an approach for PFAS analysis which uses subsampling of water matrices from vessels including centrifuge tubes and autosampler vials through the optimized use of solvent to reduce PFAS retention on subsampling vessels . Online solid phase extraction using a weak anion exchange resin is then used to concentrate sample aliquots to improve sensitivity and allow for removal of matrix interferences . With the technique of ultra performance liquid chromatography coupled to isotope dilution tandem mass spectrometry statistically based quantitation limits ranged from sub ng L to single digit ng L for carboxylate sulfonate and sulfonamide PFASs analytes from C
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Analytical bias resulting from PFAS sorption to laboratory materials did not inhibit sample throughput. Solvent addition to samples with optimized analysis conditions minimized impacts of subsampling. Quantitation with isotope dilution mass spectrometry met acceptance criteria for matched standards. The results suggest analytical factors to consider for PFASs in future studies.
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S0021967320306038
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We derive a model of band broadening in multiple open tubular columns enabling transverse diffusion . In MOTTD columns the flow channels are straight parallel cylindrical tubes arranged in a hexagonal compact array . A mesoporous material or stationary phase silica support is filling the volume between the flow channels . The model is based on Giddings random walk theory of non equilibrium chromatography . It is calibrated for the unknown configuration factor
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Multiple open tubular columns enabling transverse diffusion MOTTD are studied. Model of band broadening in MOTTD is derived from a random walk approach. Model is calibrated and validated from random walk particle tracking simulations. Difference between modeled and simulated plate heights always smaller than 10 . MOTTD columns are intrinsically superior to current packed and monolithic columns.
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S002196732030604X
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Eicosapentaenoic acid and docosahexaenoic acid are essential fatty acids for human body which are widely used in the field of healthy food and medicine . Meanwhile there are some differences in their physiological functions such as scavenger for blood vessel of EPA and brain protector of DHA . In order to make full use of EPA and DHA it is necessary to prepare their high purity component . In this paper EPA and DHA were separated and purified by three zone simulated moving bed chromatography with C18 used as stationary phase and ethanol water as mobile phase . For the single column experiment a separation unit of SMB the effects of the ratio of ethanol to water pH value and temperature on the separation were investigated . The equilibrium dispersion model was used to obtain the adsorption parameters of EPA and DHA by inverse method and genetic algorithm and the accuracy of the adsorption parameters was verified by fitting the overloaded elution curves under different conditions . Based on the acquired nonlinear adsorption isotherms the complete separation region was found according to triangle theory . The effects of sample concentration flow ratios of adsorption zone and rectification zone and column distribution mode of SMB on the separation were investigated . Under the optimized SMB conditions the experimental result was that without regard to the other components the chromatographic purity and recovery values of EPA and DHA exceeded 99 with the productivity of 4.15g L h and the solvent consumption of 1.11L g .
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Three zone SMB was adopted to separate EPA and DHA. In SMB system C18 was used as stationary phase and ethanol water pH 8 as mobile phase. The adsorption parameters were deduced based on equilibrium dispersion model. The SMB operating conditions were optimized by means of nonlinear triangle theory. EPA and DHA were separated thoroughly with recovery over 99 .
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S0021967320306099
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In this work a novel imidazolium bonding method was proposed for the synthesis of hydrophilic interaction liquid chromatography stationary phases . One obtained stationary phase was derived from direct reaction between
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A novel imidazolium bonding method were proposed for synthesis of HILIC column. Introduction of imidazolium ILs improved separation efficiency. Paired anions in ILs are proved to affect chromatographic performance. The stationary phases displayed classic HILIC characteristics. Electrostatic and polarity interaction mechanism ensure the effective separation.
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S0021967320306105
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Two structural isomeric pentacyclic triterpenes oleanolic acid and ursolic acid were considered as the models for the quality control of many traditional Chinese herbal medicines and they have been proved to own important pharmacological activities . In the present work liquid chromatographic and liquid liquid chromatographic separation with high peak resolution of structural isomeric oleanolic acid and ursolic acid using hydroxypropyl cyclodextrin as mobile phase additive was successfully achieved respectively . A high peak resolution R
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Liquid chromatography and liquid liquid chromatography of oleanolic acid and ursolic acid were achieved. High peak resolution Rs 8.0 was achieved for separation of the two components. Formation constants of inclusion complex between two components and cyclodextrin were determined. We reported an alternative method for separation of oleanolic acid and ursolic acid.
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S0021967320306117
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The ultra trace determination of nicotine and its 4 major metabolites from rabbit plasma was achieved by a newly developed solid phase microextractionliquid chromatographytandem mass spectrometry method . Extraction of the target analytes was performed with hydrophilic lipophilic balance polyacrylonitrile SPME fibers . Dual fiber extraction was necessary to guarantee improved recovery at parts per trillion levels . Liquid chromatographic analysis was achieved in a 6 min run using a C18 column with a mobile phase flow rate of 0.4mL min . Tandem mass spectrometry was used for detection and quantification in positive electrospray ionization mode for all the targeted analytes . Two stable isotope labeled internal standards were used for signal correction and accurate quantification . The mass spectrometer with laminar flow ion flux transport guaranteed improved signal stability minimal contamination of the ion guide and reproducibility into the first quadrupole analyzer . The method was validated in line with the Food and Drug Administration guidelines for bioanalytical method validation . The results met the acceptance criteria as proposed by the FDA accuracy was tested at 0.35 10 and 75g
|
Nicotine and its metabolites were quantified in rabbit plasma by SPME LC MS MS. A dual fiber extraction approach enabled analytes extraction at ppt levels. HLB PAN biocompatible SPME fibers enhanced the recovery of polar analytes. The method performances complied to FDA criteria for bioclinical method validation. Nicotine release from nicotine loaded smoking cessation formulations was evaluated.
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S0021967320306129
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A comprehensive study on the chiral separation of bupivacaine mepivacaine prilocaine and propanocaine with eight commercial polysaccharide based chiral stationary phases in reversed phase conditions compatible with MS detection is performed . Methanol and acetonitrile are used as organic modifiers . Retention and resolution values obtained for each compound in the different CSPs and mobile phases are compared . The polysaccharide based CSPs tested present different enantioselectivity towards the analytes . From the results the experimental conditions for determining the enantiomers of bupivacaine mepivacaine prilocaine and propanocaine in saline aqueous samples using MS detection are used for the first time to perform an enantioselective biodegradability study .
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Chiral separation of local anaesthetics in reversed phase conditions by LC MS. 5 cellulose and 3 amylose based chiral stationary phases CSPs compared. Acetonitrile and methanol as organic modifiers affect retention and enantioresolution. First reported chiral separation of prilocaine and propanocaine in RPLC MS. First reported enantioselective biodegradability study of local anaesthetics.
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S0021967320306130
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On spot fixed charge derivatization has been suggested for the modification of amino acids for their analysis by thin layer chromatography matrix assisted laser desorption ionization mass spectrometry . The approach was based on post chromatographic treatment of separated analytes by trismethenium salt and triethylamine . The reaction proceeded smoothly in mild conditions and gave rise to pink red colored derivatives containing permanent positive charge . Their MALDI mass spectra recorded directly from TLC plates revealed intense peaks corresponding to decarboxylated cationic parts . All derivatives are characterized by high ionization efficiency which indicates the high sensitivity of the developed method for analyzing amino acids . Applicability of the method to analysis of amino acids was demonstrated on artificial mixtures and dietary supplement .
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Post chromatographic fixed charge derivatization was used to record MALDI mass spectra of amino acids from TLC plates. Chemical labeling is based on reaction of amino acids with tris 2 6 dimethoxyphenyl methenium salt. TLC MALDI mass spectra of derivatives contain intense peaks of their decarboxylated cationic parts.
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S0021967320306142
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Thermal desorption aerosol gas chromatography mass spectrometry is capable of online measuring speciated organics in atmospheric aerosols . Compared to the one dimensional gas chromatography comprehensive two dimensional gas chromatography increases the resolution and the sensitivity mitigates the unresolved complex mixture and co elution occurred in one dimensional gas chromatography . In this study we report a quartz filter based thermal desorption aerosol comprehensive two dimensional gas chromatography mass spectrometry . It combines a solid state thermal modulator with a quartz filter based thermal desorption aerosol gas chromatography mass spectrometry . The solid state thermal modulator conducts modulation independently from the chromatographic oven without using cryogens or compressed air which makes the system readily adaptive for field measurement . The 2D Q TAG was evaluated using C7 C40 n alkanes and 16 polycyclic aromatic hydrocarbons . It has low limits of detection from 0.001 to 0.104 ng . The instrument was then deployed to measure atmospheric PM
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An online TD GCGC MS was developed for measuring organic aerosols. Major aliphatic and aromatic organics were well separated in PM. in Beijing. Time resolved quantification showed dynamic variation of different n alkanes.
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S0021967320306154
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Monitoring the levels of perfluorinated compounds in the environment is of vital importance owing to their sustained environmental presence extensive distribution and associated health risks . The development of cost effective and efficient sorbents for the establishment of sensitive analytical methods is critical for achieving trace level detection . In this study a graphitic carbon nitride g C
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A g C. based sorbent exfoliated by ZIF 67 in situ is fabricated for dSPE of PFCs. The hybrid materials possess thinner layers of g C. and small crystal of ZIF 67. The method was applied in analysis of PFCs in water samples with low MDLs.
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S0021967320306166
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Until today ion pair reversed phase chromatography is still the dominating method for analytical characterization of synthetic oligonucleotides . Its hyphenation with mass spectrometry however has some drawbacks such as ion suppression in electrospray ionization . To overcome this problem we present in this work a multiple heart cutting two dimensional liquid chromatography method with ultra violet and electrospray ionization mass spectrometry detection . A reversed phase weak anion exchange stationary phase in the first dimension
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Multiple heart cutting 2D liquid chromatography method for oligonucleotide analysis. A mixed mode RP WAX column provided high selectivity between similar oligos in. D. The. D with RPLC using a C18 column was used for desalting. The MS compatible eluent in. D devoid of ion pair allowed sensitive MS detection. Structurally closely related synthetic oligonucleotides were characterized by TOF MS.
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S0021967320306178
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We report on a systematic and comprehensive experimental study of the effect of the zone retention factor k on eddy dispersion h
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Extensive measurement set reveals a systematic k dependency of eddy dispersion. Eddy dispersion was determined using novel CFD validated Sherwood expression. Eddy dispersion data h. fit well with knox s empirical eddy dispersion model. The k dependency of the exponent and pre factor of knox s model is mapped. A simple mathematical expression to predict h. for different k is established.
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S002196732030618X
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In this study a magnetized polyethylene composite has been prepared using ball milling procedure and employed as an efficient sorbent in magnetic dispersive solid phase extraction combined with dispersive liquidliquid microextraction . This method has been utilized for the extraction and preconcentration of some pesticides from fruit juices prior to their quantification by gas chromatographyflame ionization detection . The prepared sorbent consisted of the natural iron oxide coated with polyethylene . In the present work first a few mg of the magnetic composite is added into an aqueous solution containing the analytes and vortexed . After that the analytes are eluted with
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A new analytical method based on MDSPEDLLMEGCFID was developed. For the first time a composite prepared from sand and polyethylene was used as a magnetic sorbent. The sorbent did not need synthesis and easily prepared through ball milling procedure. The method was used for analysis of multiclass pesticide residues in fruit juice. LODs and LOQs were achievable at g L. level using GC. FID.
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S0021967320306191
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The recognition and separation of polar chiral compounds are important technological challenges in separation science . Taking full advantage of the intrinsically chiral environment and multiple interactions featured by macrocycles we designed the first example of porous methylated cyclodextrins containing polymers with three dimensional chiral channels . The enantioselective recognition of
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A flexible cyclodextrin porous polymer material was synthesized. The porous materials were utilized as adsorbent for polar chiral compounds absorption. The porous materials were applied to chiral stationary phase for polar chiral compounds separation. The chiral recognition mechanism was studied in detail.
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S0021967320306208
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GCGC is an advanced separation technique allowing to achieve quantitative and qualitative characterization of complex samples . In order to perform two dimensional separation the system must provide suitable peak modulation which will direct short impulses of first column flow towards the second column . Forward fill flush differential flow modulation is a cost effective and no cryogen requiring approach which allows modulation over a wide range of analytes with very different boiling points . However optimization of the flow modulation process can be difficult to understand and quantification performance might be compromised if the parameters of the modulation process are not properly set . Modulated peak shape can be a good indication of the efficiency of the modulation process however it is not sufficient to guarantee good quantification . Different average velocities in the beginning and the end of the thermally programmed GC run may cause different efficiency of the modulation process in various parts of the chromatogram . The purpose of this work is to investigate quantitative performance of the forward fill flush modulation and delineate parameters that determine the effectiveness of the modulation process and its ability to properly reflect the quantitative composition of the investigated sample .
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Quantitative performance of forward fill flush modulation is investigated in detail. Parameters influencing efficiency of the modulation are delineated. Relation between modulated peak shape and analyte quantitation is explored. Role of the modulation fill and flush distances is explored through appropriate calculations.
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S0021967320306221
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The applicability of capillary zone electrophoresis for the separation of the deamidated forms of insulin has been studied . 50 mM NH
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CE method was developed for determination of the deamidation isoforms of insulin. 10 deamidated forms were separated and identified with CE MS. MS detection made the determination of the exact mass of the isoforms possible. The method was applied for monitoring the degradation of the insulin. In the acidified insulin solution more than 30 components could be separated.
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S0021967320306233
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Modern liquid liquid chromatography mainly refers to the following two kinds of chromatographic apparatuses countercurrent chromatography based on hydrodynamic equilibrium systems and centrifugal partition chromatography based on hydrostatic equilibrium systems . In this paper the recent advancements in enantioseparations by liquid liquid chromatography including the separation mechanism chiral selector two phase solvent system methods to improve the peak resolution and recent applications are reviewed . The future outlook for liquid liquid chromatography in enantioseparations is also proposed .
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Principles for selection of biphasic solvent systems and chiral selectors are summarized. Enantioselective liquid liquid extraction is highlighted for optimization. The ways to improve peak resolution for enantioseparation are proposed. Recent applications in enantioseparation of compounds with two chiral centers are included.
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S0021967320306245
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A molecularly imprinted polymer was synthesized and characterized to be used as solid phase extraction sorbent for simultaneous chlorpyrifos and diazinon and their oxon derivatives . Several imprinted polymers were prepared and evaluated in a retention study of these analytes compared with a non printed polymer . Several parameters affecting the extraction of imprinted polymer such as washing solvent composition and volume of the eluting solvent and sample volume were also investigated . Under the optimum conditions the developed method provided satisfactory limits of detection ranging between 0.07 g L
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Molecularly imprinted polymers for OPPs and their oxon forms were prepared. Diazinon was selected as the best template for synthesizing MIPs. MIP SPE with HPLC UV was developed for the simultaneous analysis of these pesticides. The prepared MIP sorbent showed large capacity excellent selectivity and reusability. The proposed method was successfully applied to several aqueous environmental samples.
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S0021967320306257
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Phthalate diesters are a group of plasticizers extensively used in the manufacturing and processing of plastics . Phthalate monoesters are the primary degradation products of the diesters . Accumulation of endocrine disruptive diesters and monoesters in soil is of great concern because of the extensive use of plastic mulching and misdisposal of plastics . Accurate determination of their levels in soil is critical to assess the occurrence exposure and risks of phthalate diesters and monoesters . In this study we aimed to develop a robust and environmentally friendly method for the simultaneous determination of phthalate diesters and monoesters in soil . Ultra performance liquid chromatography coupled with electrospray tandem mass spectrometry was used for quantification combined with accelerated solvent extraction and in line cleanup for sample preparation . The method detection limits for the 14 diesters and 11 monoesters were in the range of 0.59 to 10.08ng
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A method was developed to simultaneously analyze phthalate diesters and monoesters in soil. The method detection limits are in the range of 0.59 to 10.08 ng g. d.w. Previously neglected phthalate monoesters were ubiquitous in studied Chinese soil.
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S0021967320306269
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Solid phase extraction is a widely used and very well established sample preparation technique for liquid samples . An area of on going focus for innovation in this field concerns the development of new and improved SPE sorbents that can enhance the sensitivity and or the selectivity of SPE processes . In this context mixed mode ion exchange sorbents have been developed and commercialised thereby allowing enhanced capacity and selectivity to be offered by one single material . The ion selectivity of these materials is such that either anion exchange or cation exchange is possible however one limitation to their use is that more than one sorbent type is required to capture both anions and cations . In this paper we disclose the design synthesis and exploitation of a novel SPE sorbent based on microporous polymer microspheres with amphoteric character . We show that it is possible to switch the ion exchange retention mechanism of the sorbent simply by changing the pH of the loading solution anion exchange dominates at low pH cation exchange dominates at high pH and both mechanisms can contribute to retention when the polymer bound amphoteric species which are based on the amino acid sarcosine
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Preparation of microporous polymer microspheres bearing amphoteric moieties. Evaluation of the amphoteric microspheres as mixed mode ion exchange sorbent for SPE. Depending on pH its retention mechanism switched to WAX WCX or zwitterionic. Washing included to exploit the selectivity in SPE and clean the matrix. Successful ability to extract acidic and basic compounds from environmental waters.
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S0021967320306270
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In the present work a very sensitive and fully automated direct immersion PAL SPME Arrow procedure coupled with GCMS has been developed and validated for determination of nine phosphorus flame retardants in different types of water samples . PDMS DVB was selected among three commercially available SPME Arrows since it resulted in the best sensitivity . The important experimental parameters were optimized via a central composite design response surface methodology and as result extraction time of 65min extraction temperature of 80 C and added salt concentration of 19 were selected as the optimum values . The optimized method showed linear response over the calibration range 2 500ng
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SPME Arrow GCMS showed to be a powerful method for analysis of PFRs in water. Central composite design was successful in optimizing the squared and interaction factors. PFRs were detected in rain and river water samples.
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S0021967320306282
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In ionexchange chromatography the pH gradient mode becomes more and more popular today for the analysis of therapeutic proteins as this mode can provide higher or alternative selectivity to the commonly used salt gradient mode . Ideally a linear pH response is expected when performing linear gradients . However up to now only a very few buffer systems have been developed and are commercially available which can perform nearly linear pH responses when flowing through a given column . It is also known that a selected buffer system can work well on one column but can fail on other column . The goal of this study was to practically evaluate the effects that ionexchange columns might have on effluent pH when performing linear pH gradient separations of therapeutic monoclonal antibodies . To attain this objective the pH was monitored on line at the column outlet using a specific setup . To make comprehensive observations of the phenomenon four different mobile phase conditions and five cation exchange columns were employed . The obtained pH responses were systematically compared to responses measured in the absence of the columns .
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The effect of ion exchange columns on effluent pH was studied. Various buffer systems and state of the art columns were evaluated. Deviations from linear pH response might strongly depend on the column. Gradient steepness and column volume need to be considered to develop linear pH gradients.
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S0021967320306294
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Traditional polymer separation methods such as size exclusion chromatography and liquid adsorption chromatography can not provide separations exclusively based on the number of deprotonated carboxylic acid groups along the backbone chain of polymers . A novel separation method based on non aqueous ion exchange chromatography was developed which allows such a separation of acid functional polymers that are soluble in organic solvents . The polar aprotic N methyl 2 pyrrolidone was found to be a suitable solvent . It features a high relative permittivity and it is a good solvent for polymers and organic salts such as triethyl ammonium formate . A negative charge is established on these polymers by deprotonation of the carboxylic acid groups in the presence of an organic superbase . Traditional potent organic bases such as triethylamine do not possess the base strength to compensate for the increase in p
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Selective separation of carboxylic acid containing polymers according to charge. Non Aqueous Ion Exchange separation orthogonal to reversed normal phase approaches. Charge induced by organic superbase 1 1 3 3 tetramethylguanidine. Elution of adsorbed polymers by triethylammoniumformate.
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S0021967320306300
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In the present study we characterize a famous Pirkle type enantioselective stationary phase Whelk O1 from Regis Technologies and an equivalent enantiomeric phase in supercritical fluid chromatography with carbon dioxide methanol mobile phase . First the interactions contributing to retention are evaluated with a modified version of the solvation parameter model comprising five Abraham descriptors two additional descriptors to take account of molecular shape and two additional descriptors to take account of interactions with ionizable species D
|
Two Pirkle type stationary phases characterized for retention and enantioseparation. Modified LSER including ionic interactions and analyte shape features. Small spherical analytes are well included in chiral cleft and well resolved. Analytes not fitting well to the chiral cleft may still be resolved through dipole dipole and H bond interactions.
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S0021967320306324
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The Al doped mesoporous crystalline material 41 composite was prepared and applied as fiber coating material of headspace solid phase microextraction for extraction of polycyclic aromatic hydrocarbons from human urine . Five PAHs including acenaphthene fluorene phenanthrene anthracene and pyrene are chosen as target analytes to evaluate the performance of the material by GC FID analysis . The mesoporous Al MCM 41 composite was characterized by scanning electron microscopy transmission electron microscopy X ray diffraction Fourier transform infrared spectroscopy nitrogen adsorption desorption measurement and thermogravimetric analysis . The parameters affecting the extraction efficiency of HS SPME were investigated . Under the optimal conditions the method exhibits ideal linearity for target analytes in the range of 0.3600 ngmL
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The Al doped mesoporous crystalline material 41 Al MCM 41 mesoporous material was prepared. Al MCM 41 as the new fiber coating material of solid phase microextraction SPME . Headspace SPME was developed to extract polycyclic aromatic hydrocarbons PAHs . Five PAHs in human urine were extracted and preconcentrated by headspace SPME. Sensitive detection of PAHs with GC FID using Al MCM 41 as coating material of SPME.
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S0021967320306336
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Quantification of the gas streams from chemical systems such as catalytic reactors are routinely performed by on line gas chromatography . Gas chromatographs used for this purpose are typically provided with a combination of thermal conductivity and flame ionization detectors to be able to detect and quantify both permanent gases CO
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A method for characterizing gas streams with on line gas chromatography was designed. The on line GC was provided with a TCD methanizer FID system of detection. Quantification methods were developed considering mass balances in the system. The internal and external standard methods for quantification were compared. The internal standard method produced highly accurate mass balances.
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S0021967320306348
|
The presence of organophosphate esters in everyday commodities such as furniture household appliances and baby toys have rendered these contaminants ubiquitous in environmental fates such as air water soils and biota . Their presence in food related species suggests that an additional route of exposure to these esters for the general population is fish intake through diet . Their incipient toxicity and carcinogenetic behaviour make it essential to develop methods for determining OPEs in fish samples . In this paper we have developed a new method for determining 9 OPEs based on the QuEChERS extraction method followed by a simple clean up using a novel device for selective lipid removal and GCMS MS to extract these compounds from fish samples regardless of lipid content . QuEChERS salt packet optimisation and clean up strategies such as liquid liquid extraction dispersive solid phase extraction and LipiFiltr were tested . Our results showed that EN 15662 method salts and Lipifiltr were the best combination to produce efficient analyte apparent recovery and negligible matrix effects . Limits of detection ranged from 0.05ng g
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A new QuEChERS GC MS MS method for OPEs in fish has been successfully developed. Clean up using the novel LipiFiltr greatly reduced lipidic fish matrix. Median concentration of OPEs found at the fish species was 5.31ng g. w.w. . Estimates of exposure and risk via dietary intake showed low levels of concern.
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S002196732030635X
|
In this study the in situ conversion of the synthesized Co Al layered double hydroxide nanosheets to three dimensional hierarchical zeolitic imidazolate framework 67 was presented as a cost effective highly efficient flexible and robust sorbent to carry out the microextraction process . In the first stage the anodized aluminum foil was prepared electrochemically . Then the Co Al LDH precursor was constructed on the surface of the previously prepared anodized Al foil applying in situ formation approach . The procedure is followed by the conversion of the prepared Co Al LDH film to 3D HZIF 67 film via a facile solvothermal method without adding cobalt salt . The in situ prepared 3D HZIF 67 anodized Al was used for the thin film microextraction of caffeine . The effective factors in TFME procedure were investigated and optimized through applying Central Composite Design . In the obtained optimal condition the calibration curves for TFME HPLC UV of caffeine were linear in the range of 1200g
|
3D HZIF 67 as a cost effective flexible and robust sorbent for TFME was presented. LDH precursor was constructed on the surface of a very cheap anodized Al foil. Conversion of the LDH to HZIF 67 film was performed via a facile solvothermal method. The sorbent was used for analysis of caffeine in urine followed by HPLC UV. The method shows low LOD LOQ and proper LDR with acceptable precision.
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S0021967320306361
|
The enantiomeric determination of chiral drugs in the environment is of emerging concern since their enantiomers often exhibit stereoselectivity in environmental occurrence fate and toxicity . In this study a method based on solid phase extraction followed by chiral liquid chromatography and high resolution mass spectrometry has been developed for the enantiomeric determination of a group of cathinones in river water and effluent wastewater . The enantioseparation was carried out using a Chiralpak CBH column in reversed phase mode and optimised by evaluating the effects of flow rate buffer concentration and organic modifier . Under optimal conditions good enantioseparations R
|
First study on enantiomeric determination of a group of cathinones in environment. An SPE LC. HRMS method was developed for the enantiomeric determination of cathinones. Good recoveries were achieved with an oasis MCX cartridge. Clear influence of sample matrix on the t. and r. when oasis WCX cartridge was used.
|
S0021967320306373
|
Conjugated microporous polymers with uniform morphology have shown fascinating application in the separation science . In this study metal free Knoevenagel condensation was adopted to prepare spherical
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Spherical. carbon conjugated microporous polymers. c CMPs were prepared. Surface areas of. c CMPs can be regulated by inorganic salt. c CMPs were used as solid phase microextraction SPME coating. SPME method was established for detecting carbamate pesticides in water.
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S0021967320306385
|
The alkaloid enantiomers are well known to have different physiological and pharmacological effects and to play an important role in enantioselectivity metabolism with enzymes catalysis in tobacco plants . Here we developed an improved method for simultaneous and high precision determination of the individual enantiomers of nornicotine anatabine and anabasine in four tobacco matrices based on an achiral gas chromatography nitrogen phosphorus detector GC
|
Chiral derivatization combining achiral GC was applied to analyze alkaloid enantiomer. camphanic chloride derivatization was optimized by Box Benhnken design. This method is validated for the identification of unknown alkaloids. Cultivar has significant impact on enantiomer fraction of. nornicotine. Enantiomer fraction of. anabasine shows a significant increase in curing processes.
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S0021967320306397
|
Exploring new material as adsorbent for the efficient enrichment of pollutants is always of great significance in analytical chemistry . In this work a magnetic azobenzene framework was constructed as a magnetic solid phase extraction adsorbent by a simple and environmentally benign strategy . The MAzo exhibited the attractive features of strong magnetism outstanding adsorption performance as well as good reusability . Combining MAzo based MSPE with high performance liquid phase chromatography a simple and effective method was developed for simultaneous determination of four phenylurea herbicides in pear juice and apple juice samples . Under optimized experimental conditions the method offered low limits of detection of 0.05 0.15 ng mL
|
A magnetic azobenzene framework was synthesized by an environmentally benign method. The adsorbent displayed good adsorption performance for phenylurea herbicides PUHs . A sensitive method was applied for detection of PUHs in pear and apple juice samples.
|
S0021967320306403
|
Analytical techniques to determine volatile compounds such as flavor aroma and fragrances are in high demand due to their wide range of applications in industry the chemical properties of them are very diverse . Supercritical fluid chromatography is capable of high speed high peak capacity separation and has a high separation coverage . It is also an advantageous for preparative purifications due to its unique mobile phase conditions . However there is no column commercially available for SFC that is suitable to comprehensively separate volatile compounds . SFC is limited to the use of silica based columns due to weak retentions and polymer based column issues such as pressure swelling and shrinkage tolerances . This study demonstrated comprehensive analytical method for volatile in SFC using a highly cross linked styrene divinylbenzene polymer based column newly developed for SFC . In this study 23 typical volatile compounds with a wide variety of chemical properties were selected as model compounds . The newly developed SDVB column showed compared to conventional silica based columns an excellent overall and substantial improved retentions under SFC mobile phase conditions . It was also able to retain esters and non polar terpenes that did not show sufficient retention in any other commercially available silica based columns . Aldehydes reacting on NH
|
Highly cross linked styrene divinylbenzene SDVB polymer based column brought excellent retention and separation of volatile compounds especially the esters and non polar terpenes in SFC. Although retention mechanism based on interactions of SDVB and Phenyl column is similar higher specific area of novel SDVB column than that of Phenyl column contributed to the better retention. The results provided reasons to not only further develop the profiling of volatile compounds on analytical scale but also the purification and production on prep scale.
|
S0021967320306415
|
A new type of restricted access media imprinted nanomaterials were successfully prepared on the surface of metal organic framework by reversible addition fragmentation chain transfer polymerization technology . Then it was applied as a dispersed solid phase extraction material in analysis of fluoroquinolones in untreated milk and river water by HPLC UV detection . The resulted material has a good binding amounts 60.81mg g
|
RAM MIPs based on MOF were prepared as DSPE material. The method extracted FQs directly from untreated milk and river water successfully. RAM MIPs possessed satisfactory protein exclusion properties.
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