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Selected papers from the latest issue:
Capillary electrophoresis methods for the analysis of antimalarials. Part I. Chiral separation methods
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
N’Cho Christophe Amin, Marie-Dominique Blanchin, Michèle Aké, Huguette Fabre
This paper presents an overview on the current status of enantiomeric and diastereomeric separations of chiral antimalarials and derivatives by capillary electrophoresis (CE). The wide variety of chiral selectors which have been employed to resolve successfully antimalarial enantiomers: oligosaccharides (cyclodextrins, oligomaltodextrins), neutral (amylose, dextrin and dextran) and charged (chondroitin sulfate, heparin, dextran sulfate) polysaccharides and proteins are reviewed. Cyclodextrins were the most employed. Chiral additives added to the background electrolyte often facilitated separations of quinine/quinidine and cinchonine/cinchonidine diastereomers. However, in a few cases, using micellar electrokinetic capillary chromatography or non aqueous CE, resolution of diastereomers could be achieved without additives. Quantitative applications of CE to the quality control of antimalarial drugs and their analysis in biological and food matrices are presented.
Source:Journal of Chromatography A, Volume 1264
N’Cho Christophe Amin, Marie-Dominique Blanchin, Michèle Aké, Huguette Fabre
This paper presents an overview on the current status of enantiomeric and diastereomeric separations of chiral antimalarials and derivatives by capillary electrophoresis (CE). The wide variety of chiral selectors which have been employed to resolve successfully antimalarial enantiomers: oligosaccharides (cyclodextrins, oligomaltodextrins), neutral (amylose, dextrin and dextran) and charged (chondroitin sulfate, heparin, dextran sulfate) polysaccharides and proteins are reviewed. Cyclodextrins were the most employed. Chiral additives added to the background electrolyte often facilitated separations of quinine/quinidine and cinchonine/cinchonidine diastereomers. However, in a few cases, using micellar electrokinetic capillary chromatography or non aqueous CE, resolution of diastereomers could be achieved without additives. Quantitative applications of CE to the quality control of antimalarial drugs and their analysis in biological and food matrices are presented.
Highlights
► Exhaustive review of chiral capillary electrophoresis (CE) methods for antimalarials. ► Chiral selectors for enantiomeric and diastereomeric separations in CE. ► Quantitative applications.Novel software-based method to classify structurally similar compounds combined with high performance liquid chromatography–quadrupole time of flight mass spectrometry to identify complex components of herbal medicines
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Qi-Yuan Shan, Gang Cao, Hao Cai, Xiao-Dong Cong, Bao-Chang Cai
The components of herbal medicines (HMs) are usually extremely complex, belonging to hundreds of compound classes with diverse chemical and physical properties. Full characterization of HMs is hugely important in order to identify the individual chemical constituents and provide a first step toward determining which components are responsible for the therapeutic effects of a particular medical plant. In this study, a novel software-based approach was developed to classify structurally similar compounds, and this was combined with high performance liquid chromatography/quadrupole time-of-flight mass spectrometry (HPLC–QTOF-MS) to identify the individual components in an extract of Mentha haplocalyx. A total of 33 compounds were tentatively identified in samples of M. haplocalyx extract, including 9 new minor constituents reported for the first time. Semi-quantitative analysis of the extract sample was also carried out. Software validation and robustness tests were performed. The results of this study demonstrate the enormous potential of this strategy, using classification based on structural similarity together with HPLC–QTOF-MS, for the identification and quantification of complex components in HMs and related products.
Source:Journal of Chromatography A, Volume 1264
Qi-Yuan Shan, Gang Cao, Hao Cai, Xiao-Dong Cong, Bao-Chang Cai
The components of herbal medicines (HMs) are usually extremely complex, belonging to hundreds of compound classes with diverse chemical and physical properties. Full characterization of HMs is hugely important in order to identify the individual chemical constituents and provide a first step toward determining which components are responsible for the therapeutic effects of a particular medical plant. In this study, a novel software-based approach was developed to classify structurally similar compounds, and this was combined with high performance liquid chromatography/quadrupole time-of-flight mass spectrometry (HPLC–QTOF-MS) to identify the individual components in an extract of Mentha haplocalyx. A total of 33 compounds were tentatively identified in samples of M. haplocalyx extract, including 9 new minor constituents reported for the first time. Semi-quantitative analysis of the extract sample was also carried out. Software validation and robustness tests were performed. The results of this study demonstrate the enormous potential of this strategy, using classification based on structural similarity together with HPLC–QTOF-MS, for the identification and quantification of complex components in HMs and related products.
Highlights
► A novel software-based method is developed to analyze herbal medicines. ► The method is based on structurally similar classification of compounds. ► 33 compounds were tentatively identified in samples of Mentha haplocalyx extract. ► Including 9 new minor constituents were reported for the first time.Superficially porous silica particles with wide pores for biomacromolecular separations
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Brian M. Wagner, Stephanie A. Schuster, Barry E. Boyes, Joseph J. Kirkland
Since 2006, columns of superficially porous particles (SPPs), often called Fused-core®, porous–shell or core–shell particles, have had serious impact on HPLC separations. These particles have pore diameters of about 100Å designed for separating small molecules. More recently, SPPs with 160–200Å pore diameter have been made available for separating peptides and small proteins. This report describes the effects of fused-core particle size, pore size, shell thickness and ligand type for the rapid, efficient separation of larger molecules such as intact proteins and other biomacromolecules up to at least 400kDa. Optimization of these parameters resulted in particles that show no restricted diffusion that would compromise separating efficiency for large biomolecules. The thin porous shell provides excellent mass transfer (kinetics) for these large molecules, resulting in superior separations compared to conventional totally porous particles. Sample loading capacity can be adjusted to allow good detection sensitivity for minor components in a complex mixture. Strong particle strength ensures the loading of stable, high-efficiency columns. Stationary phases with different alkyl ligands were tested to provide data on retention, column efficiency and peak shapes for proteins. The development of these new wide-pore fused-core particles now allows the HPLC separation of a wide range of molecules of different sizes with advantages of the SPP configuration.
Source:Journal of Chromatography A, Volume 1264
Brian M. Wagner, Stephanie A. Schuster, Barry E. Boyes, Joseph J. Kirkland
Since 2006, columns of superficially porous particles (SPPs), often called Fused-core®, porous–shell or core–shell particles, have had serious impact on HPLC separations. These particles have pore diameters of about 100Å designed for separating small molecules. More recently, SPPs with 160–200Å pore diameter have been made available for separating peptides and small proteins. This report describes the effects of fused-core particle size, pore size, shell thickness and ligand type for the rapid, efficient separation of larger molecules such as intact proteins and other biomacromolecules up to at least 400kDa. Optimization of these parameters resulted in particles that show no restricted diffusion that would compromise separating efficiency for large biomolecules. The thin porous shell provides excellent mass transfer (kinetics) for these large molecules, resulting in superior separations compared to conventional totally porous particles. Sample loading capacity can be adjusted to allow good detection sensitivity for minor components in a complex mixture. Strong particle strength ensures the loading of stable, high-efficiency columns. Stationary phases with different alkyl ligands were tested to provide data on retention, column efficiency and peak shapes for proteins. The development of these new wide-pore fused-core particles now allows the HPLC separation of a wide range of molecules of different sizes with advantages of the SPP configuration.
Highlights
► New 400Å pore size particles separate large proteins without restricted diffusion. ► Particles with larger surface areas allow greater sample mass loading. ► Particles with thinner shells show higher efficiency for proteins. ► New wide-pore superficially porous particles demonstrate excellent stability. ► Particles with C4 and C8 stationary phases appear superior for some protein separations.Evaluation of hydrophilic interaction chromatography (HILIC) versus C18 reversed-phase chromatography for targeted quantification of peptides by mass spectrometry
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Romain Simon, Quentin Enjalbert, Jordane Biarc, Jérôme Lemoine, Arnaud Salvador
Hydrophilic-interaction liquid chromatography (HILIC) is a widely used technique for small polar molecule analysis and offers the advantage of improved sensitivity in mass spectrometry. Although HILIC is today frequently employed as an orthogonal fractionation method for peptides during the proteomic discovery phase, it is still seldom considered for quantification. In this study, the performances in terms of peak capacity and sensitivity of 3 HILIC columns were compared to traditional reversed phase liquid C18 column in the context of targeted quantification of proteotypic peptides using selected reaction monitoring mode (SRM). The results showed that the maximum sensitivity in HILIC chromatography was achieved by using an amide column without salt buffer and that the signal increased compared to classic reversed phase chromatography. However, the intensity improvement is quite low compared to the one obtained for small molecules. This is due on one hand to a higher matrix effect in HILIC and on the other hand to a change of charge states of peptides in organic solvent (doubly charged to monocharged). The doubly charged ions can be more readily dissociated than singly charged ions, making them ideal for SRM peptide quantification. As a result “supercharging” reagents are added to the mobile phase to shift from predominant singly charged ions to the more favorable doubly charged species. Using such optimized conditions, peptide signal is improved by a factor of between two and ten for 88% of the peptides of the 81 peptides investigated.
Source:Journal of Chromatography A, Volume 1264
Romain Simon, Quentin Enjalbert, Jordane Biarc, Jérôme Lemoine, Arnaud Salvador
Hydrophilic-interaction liquid chromatography (HILIC) is a widely used technique for small polar molecule analysis and offers the advantage of improved sensitivity in mass spectrometry. Although HILIC is today frequently employed as an orthogonal fractionation method for peptides during the proteomic discovery phase, it is still seldom considered for quantification. In this study, the performances in terms of peak capacity and sensitivity of 3 HILIC columns were compared to traditional reversed phase liquid C18 column in the context of targeted quantification of proteotypic peptides using selected reaction monitoring mode (SRM). The results showed that the maximum sensitivity in HILIC chromatography was achieved by using an amide column without salt buffer and that the signal increased compared to classic reversed phase chromatography. However, the intensity improvement is quite low compared to the one obtained for small molecules. This is due on one hand to a higher matrix effect in HILIC and on the other hand to a change of charge states of peptides in organic solvent (doubly charged to monocharged). The doubly charged ions can be more readily dissociated than singly charged ions, making them ideal for SRM peptide quantification. As a result “supercharging” reagents are added to the mobile phase to shift from predominant singly charged ions to the more favorable doubly charged species. Using such optimized conditions, peptide signal is improved by a factor of between two and ten for 88% of the peptides of the 81 peptides investigated.
Highlights
► Gain in sensitivity for peptide quantitation in HILIC by LC–MS was evaluated for the first time. ► HILIC mobile phases promote monocharged peptides. ► With supercharging reagents sensitivity was enhanced by a factor 2–10.An improved high performance liquid chromatography-fluorescence detection method for the analysis of major phenolic compounds in cigarette smoke and smokeless tobacco products
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Jingcun Wu, William S. Rickert, Andrew Masters
An improved HPLC method has been developed for the determination of major phenolic compounds in cigarette smoke. A novel reversed phase column with a pentafluorophenylpropyl (PFP) ligand in the stationary phase was chosen to separate the positional isomers (p-, m-, and o-cresols). Methanol instead of acetonitrile was used as the organic mobile phase component to improve the separation of the isomers and cope with the crisis of global acetonitrile shortage in 2009. A shorter analytical column with smaller particle size was used to further increase separation efficiency and reduces solvent consumption. These improvements have led to a new HPLC method that is simpler and faster than the GC–MS method and more sensitive, selective and efficient than the widely used traditional HPLC method. The limit of detection (LOD) and limit of quantification (LOQ) of this method are at the ng/mL level for most of the phenols with good linearity (R 2 ≥0.999) and precision (RSD<15%). The method has been validated using reference tobacco products. The mainstream and sidestream cigarette smoke yields of phenolic compounds obtained by this method are comparable to those obtained by traditional HPLC method with the advantage that p-, m-, and o-cresols can be determined and reported separately by the new method. The method can also be applied for analysis of phenols in smokeless tobacco product.
Source:Journal of Chromatography A, Volume 1264
Jingcun Wu, William S. Rickert, Andrew Masters
An improved HPLC method has been developed for the determination of major phenolic compounds in cigarette smoke. A novel reversed phase column with a pentafluorophenylpropyl (PFP) ligand in the stationary phase was chosen to separate the positional isomers (p-, m-, and o-cresols). Methanol instead of acetonitrile was used as the organic mobile phase component to improve the separation of the isomers and cope with the crisis of global acetonitrile shortage in 2009. A shorter analytical column with smaller particle size was used to further increase separation efficiency and reduces solvent consumption. These improvements have led to a new HPLC method that is simpler and faster than the GC–MS method and more sensitive, selective and efficient than the widely used traditional HPLC method. The limit of detection (LOD) and limit of quantification (LOQ) of this method are at the ng/mL level for most of the phenols with good linearity (R 2 ≥0.999) and precision (RSD<15%). The method has been validated using reference tobacco products. The mainstream and sidestream cigarette smoke yields of phenolic compounds obtained by this method are comparable to those obtained by traditional HPLC method with the advantage that p-, m-, and o-cresols can be determined and reported separately by the new method. The method can also be applied for analysis of phenols in smokeless tobacco product.
Highlights
► The HPLC method for phenols analysis in tobacco smoke was improved significantly. ► Cresol isomers were separated for the first time by a HPLC method. ► Using methanol in mobile phases, this method cut solvent cost for phenols analyses. ► A shorter column was used to enhance separation and reduce analytical cost. ► The method was also used for phenols analysis in smokeless tobacco products.Multicomponent adsorption of monoclonal antibodies on macroporous and polymer grafted cation exchangers
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Ernie X. Perez-Almodovar, Yige Wu, Giorgio Carta
We compare the rates of adsorption of two monoclonal antibodies (mAbs) with different adsorption properties on the cation exchangers UNOsphere™ S and Nuvia™ S. The former contains large open pores while the latter is based on a backbone matrix similar to UNOsphere™ S but also contains grafted charged polymers. Both single component and two-component adsorption are considered. Adsorption capacity and rates are much higher for Nuvia™ S indicating that protein interactions with the charged grafted polymers facilitate both binding and diffusional transport. Intraparticle concentration profiles obtained by confocal microscopy show sharp fronts for UNOsphere™ S but diffuse profiles for Nuvia™ S. Transport is thus controlled by pore diffusion for UNOsphere™ S but is described by a single file diffusion (SFD) mechanism for Nuvia™ S. As a result, single and two-component adsorption occur at similar rates for UNOsphere™ S independent of the direction for transport. For Nuvia™ S, however, transport is very fast for single or two-component co-adsorption but very slow when counter diffusion of the two mAbs takes place within the particles. The transport models developed in this work allow a prediction of separation performance for overloaded conditions typical of process scale applications.
Source:Journal of Chromatography A, Volume 1264
Ernie X. Perez-Almodovar, Yige Wu, Giorgio Carta
We compare the rates of adsorption of two monoclonal antibodies (mAbs) with different adsorption properties on the cation exchangers UNOsphere™ S and Nuvia™ S. The former contains large open pores while the latter is based on a backbone matrix similar to UNOsphere™ S but also contains grafted charged polymers. Both single component and two-component adsorption are considered. Adsorption capacity and rates are much higher for Nuvia™ S indicating that protein interactions with the charged grafted polymers facilitate both binding and diffusional transport. Intraparticle concentration profiles obtained by confocal microscopy show sharp fronts for UNOsphere™ S but diffuse profiles for Nuvia™ S. Transport is thus controlled by pore diffusion for UNOsphere™ S but is described by a single file diffusion (SFD) mechanism for Nuvia™ S. As a result, single and two-component adsorption occur at similar rates for UNOsphere™ S independent of the direction for transport. For Nuvia™ S, however, transport is very fast for single or two-component co-adsorption but very slow when counter diffusion of the two mAbs takes place within the particles. The transport models developed in this work allow a prediction of separation performance for overloaded conditions typical of process scale applications.
Highlights
► Single and multiple mAbs adsorption in macroporous resins is pore diffusion controlled. ► Single and multiple mAbs adsorption in grafted resins is solid diffusion controlled. ► Adsorption rates depend on composition for polymer-grafted resins. ► Single file diffusion model predicts adsorption kinetics in grafted resins.High-resolution separations of tryptic digest mixtures using core–shell particulate columns operated at 1200bar
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Jelle De Vos, Catherine Stassen, Axel Vaast, Gert Desmet, Sebastiaan Eeltink
Combining two recent advances in instrumentation and column technology (ultra-high-pressure LC instruments and core–shell particles), the current peak-capacity generation limits in one-dimensional LC have been explored for the case of tryptic digest separations. To operate as close as possible to the Knox and Saleem limit of the particles, and hence to operate the 2.6μm core–shell particles at their kinetic optimum, the separations were conducted in a coupled column systems at 1200bar. Using coupled columns with a total length of 450mm at 1200bar and applying 40 and 120min gradients (t G /t 0 =17 and 52, respectively), peak capacities of n c =480 and 760 were measured. The kinetic performance was further improved by coupling six 150mm long columns and applying 1200bar, yielding a flow rate close to the optimum of the van Deemter curve while scaling the gradient volume. At t G /t 0 =52 a peptide separation yielding a peak capacity of 1360 was achieved, applying a 480min gradient. The observed increase of peak capacity with column length agrees well with the theoretical expectations based on the linear solvent strength (LSS) model.
Source:Journal of Chromatography A, Volume 1264
Jelle De Vos, Catherine Stassen, Axel Vaast, Gert Desmet, Sebastiaan Eeltink
Combining two recent advances in instrumentation and column technology (ultra-high-pressure LC instruments and core–shell particles), the current peak-capacity generation limits in one-dimensional LC have been explored for the case of tryptic digest separations. To operate as close as possible to the Knox and Saleem limit of the particles, and hence to operate the 2.6μm core–shell particles at their kinetic optimum, the separations were conducted in a coupled column systems at 1200bar. Using coupled columns with a total length of 450mm at 1200bar and applying 40 and 120min gradients (t G /t 0 =17 and 52, respectively), peak capacities of n c =480 and 760 were measured. The kinetic performance was further improved by coupling six 150mm long columns and applying 1200bar, yielding a flow rate close to the optimum of the van Deemter curve while scaling the gradient volume. At t G /t 0 =52 a peptide separation yielding a peak capacity of 1360 was achieved, applying a 480min gradient. The observed increase of peak capacity with column length agrees well with the theoretical expectations based on the linear solvent strength (LSS) model.
Highlights
► High-resolution peptide separations were obtained with 2.6μm core–shell particles. ► A peak capacity of 760 was obtained in 2h on a 450mm coupled column system. ► Operating a 900mm coupled system at 1200bar yielded a peak capacity of 1360.Fast analysis of synthetic antioxidants in edible vegetable oil using trilinear component modeling of liquid chromatography–diode array detection data
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Jian-Yao Wang, Hai-Long Wu, Yao Chen, Yan-Mei Sun, Yong-Jie Yu, Xiao-Hua Zhang, Ru-Qin Yu
A new chromatographic methodology is presented for fast quantitative analysis of ten synthetic phenolic antioxidants in five kinds of oil samples: propyl gallate (PG), 2,4,5-trihydroxybutyrophenone (THBP), tert-butylhydroquinone (TBHQ), nordihydroguaiaretic acid (NDGA), ethoxyquin (EQ), 3-tert-butyl-4- hydroxyanisole (BHA), octyl gallate (OG), 2,6-di-tert-butyl-4-hydroxymethyphenol (Ionox-100), dodecyl gallate (DG), 3,5-di-tert-butyl-4-hydroxytoluene (BHT). The second-order calibration, with second-order advantage, based on the alternating penalty trilinear decomposition (APTLD) algorithm has shown to be an excellent tool for modeling the three-way data, where overlapping peaks, uncalibrated inteferences, and baseline drift existed, making the fast determination and resolution of the phenolic antioxidants in oils possible. Such extraction procedure in which the antioxidants of interest would be seperated is unnecessary and the ten antioxidants can be eluted within 6mins. For the validation of the method, linearity, root-mean-square error of prediction (RMSEP) and limit of detection (LOD) have been performed. The average recovery of antioxidants ranges from 94.9 to 106.1% and the ten analytes can be adequately determined with limits of detection of 0.18–5.72μgml−1.
Source:Journal of Chromatography A, Volume 1264
Jian-Yao Wang, Hai-Long Wu, Yao Chen, Yan-Mei Sun, Yong-Jie Yu, Xiao-Hua Zhang, Ru-Qin Yu
A new chromatographic methodology is presented for fast quantitative analysis of ten synthetic phenolic antioxidants in five kinds of oil samples: propyl gallate (PG), 2,4,5-trihydroxybutyrophenone (THBP), tert-butylhydroquinone (TBHQ), nordihydroguaiaretic acid (NDGA), ethoxyquin (EQ), 3-tert-butyl-4- hydroxyanisole (BHA), octyl gallate (OG), 2,6-di-tert-butyl-4-hydroxymethyphenol (Ionox-100), dodecyl gallate (DG), 3,5-di-tert-butyl-4-hydroxytoluene (BHT). The second-order calibration, with second-order advantage, based on the alternating penalty trilinear decomposition (APTLD) algorithm has shown to be an excellent tool for modeling the three-way data, where overlapping peaks, uncalibrated inteferences, and baseline drift existed, making the fast determination and resolution of the phenolic antioxidants in oils possible. Such extraction procedure in which the antioxidants of interest would be seperated is unnecessary and the ten antioxidants can be eluted within 6mins. For the validation of the method, linearity, root-mean-square error of prediction (RMSEP) and limit of detection (LOD) have been performed. The average recovery of antioxidants ranges from 94.9 to 106.1% and the ten analytes can be adequately determined with limits of detection of 0.18–5.72μgml−1.
Highlights
► Ten Synthetic phenolic antioxidants (SPAs) can be eluted within 6min. ► The extraction of the SPAs in oils is unnecessary. ► Baseline drift and peak overlapping were successfully resolved by our method.Impact of carrier fluid composition on recovery of nanoparticles and proteins in flow field flow fractionation
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Samantha Schachermeyer, Jonathan Ashby, MinJung Kwon, Wenwan Zhong
Flow field flow fractionation (F4) is an invaluable separation tool for large analytes, including nanoparticles and biomolecule complexes. However, sample loss due to analyte-channel membrane interaction limits extensive usage of F4 at present, which could be strongly affected by the carrier fluid composition. This work studied the impacts of carrier fluid (CF) composition on nanoparticle (NP) recovery in F4, with focus on high ionic strength conditions. Successful analysis of NPs in a biomolecules-friendly environment could expand the applicability of F4 to the developing field of nanobiotechnology. Recovery of the unfunctionalized polystyrene NPs of 199, 102, and 45nm in CFs with various pH (6.2, 7.4 and 8.2), increasing ionic strength (0–0.1M), and different types of co- and counter-ions, were investigated. Additionally, elution of the 85nm carboxylate NPs and two proteins, human serum albumin (HSA) and immunoglobulin (IgG), at high ionic strengths (0–0.15M) was investigated. Our results suggested that (1) electrostatic repulsion between the negatively charged NPs and the regenerated cellulose membrane was the main force to avoid particle adsorption on the membrane; (2) larger particles experienced higher attractive force and thus were influenced more by variation in CF composition; and (3) buffers containing weak anions or NPs with weak anion as the surface functional groups provided higher tolerance to the increase in ionic strength, owing to more anions being trapped inside the NP porous structure. Protein adsorption onto the membrane was also briefly investigated in salted CFs, using HSA and IgG. We believe our findings could help to identify the basic carrier fluid composition for higher sample recovery in F4 analysis of nanoparticles in a protein-friendly environment, which will be useful for applying F4 in bioassays and in nanotoxicology studies.
Source:Journal of Chromatography A, Volume 1264
Samantha Schachermeyer, Jonathan Ashby, MinJung Kwon, Wenwan Zhong
Flow field flow fractionation (F4) is an invaluable separation tool for large analytes, including nanoparticles and biomolecule complexes. However, sample loss due to analyte-channel membrane interaction limits extensive usage of F4 at present, which could be strongly affected by the carrier fluid composition. This work studied the impacts of carrier fluid (CF) composition on nanoparticle (NP) recovery in F4, with focus on high ionic strength conditions. Successful analysis of NPs in a biomolecules-friendly environment could expand the applicability of F4 to the developing field of nanobiotechnology. Recovery of the unfunctionalized polystyrene NPs of 199, 102, and 45nm in CFs with various pH (6.2, 7.4 and 8.2), increasing ionic strength (0–0.1M), and different types of co- and counter-ions, were investigated. Additionally, elution of the 85nm carboxylate NPs and two proteins, human serum albumin (HSA) and immunoglobulin (IgG), at high ionic strengths (0–0.15M) was investigated. Our results suggested that (1) electrostatic repulsion between the negatively charged NPs and the regenerated cellulose membrane was the main force to avoid particle adsorption on the membrane; (2) larger particles experienced higher attractive force and thus were influenced more by variation in CF composition; and (3) buffers containing weak anions or NPs with weak anion as the surface functional groups provided higher tolerance to the increase in ionic strength, owing to more anions being trapped inside the NP porous structure. Protein adsorption onto the membrane was also briefly investigated in salted CFs, using HSA and IgG. We believe our findings could help to identify the basic carrier fluid composition for higher sample recovery in F4 analysis of nanoparticles in a protein-friendly environment, which will be useful for applying F4 in bioassays and in nanotoxicology studies.
Highlights
► High repulsive force between NPs and membrane can minimize particle adsorption. ► Weaker anion in solution or on NP surface causes lower NP adsorption at high conc. ► Highly charged counter ions increases NP adsorption on membrane significantly. ► Protein conformation plays an important role in protein–membrane interaction.Development of heart-cutting multidimensional gas chromatography coupled to time of flight mass spectrometry for silicon speciation at trace levels in gasoline samples
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Fabien Chainet, Charles-Philippe Lienemann, Jérémie Ponthus, Marion Courtiade, Olivier François Xavier Donard
To improve the understanding of hydrotreatment (HDT) catalyst poisoning by silicon species, these molecules must be characterized in petroleum products using powerful analytical systems. Heart-cutting gas chromatography coupled to time of flight mass spectrometry (GC–GC/TOFMS) method equipped with a Deans switch (DS) system was developed for the direct characterization of target silicon compounds at trace level (μgkg−1) in gasoline samples. This method was performed to identify silicon compounds never characterized before. After the selection of the second dimension column using GC–GC–FID, GC–GC/TOFMS was performed. The calibration curves obtained by the GC–GC/TOFMS method were linear up to 1000μgkg−1. Limits of detection (LOD) were ranging from 5 to 33μgkg−1 in spiked gasoline. The method provided sufficient selectivity and sensitivity to characterize known silicon compounds thanks to their specific ions and their retention times. The analysis of a naphtha sample by GC–GC/TOFMS has shown the presence of cyclic siloxanes (D n ) as major compounds of PDMS thermal degradation with the occurrence of linear siloxanes, especially hexamethyldisiloxane (L2), which was never characterized in petroleum products but already known as severe poison for catalyst.
Source:Journal of Chromatography A, Volume 1264
Fabien Chainet, Charles-Philippe Lienemann, Jérémie Ponthus, Marion Courtiade, Olivier François Xavier Donard
To improve the understanding of hydrotreatment (HDT) catalyst poisoning by silicon species, these molecules must be characterized in petroleum products using powerful analytical systems. Heart-cutting gas chromatography coupled to time of flight mass spectrometry (GC–GC/TOFMS) method equipped with a Deans switch (DS) system was developed for the direct characterization of target silicon compounds at trace level (μgkg−1) in gasoline samples. This method was performed to identify silicon compounds never characterized before. After the selection of the second dimension column using GC–GC–FID, GC–GC/TOFMS was performed. The calibration curves obtained by the GC–GC/TOFMS method were linear up to 1000μgkg−1. Limits of detection (LOD) were ranging from 5 to 33μgkg−1 in spiked gasoline. The method provided sufficient selectivity and sensitivity to characterize known silicon compounds thanks to their specific ions and their retention times. The analysis of a naphtha sample by GC–GC/TOFMS has shown the presence of cyclic siloxanes (D n ) as major compounds of PDMS thermal degradation with the occurrence of linear siloxanes, especially hexamethyldisiloxane (L2), which was never characterized in petroleum products but already known as severe poison for catalyst.
Highlights
► A GC–GC/TOFMS was developed for the characterization of silicon compounds. ► Silicon species, potentially poisons, were identified at trace levels. ► A real advance for silicon speciation to understand catalyst poisoning.Fully automated determination of macrocyclic musk fragrances in wastewater by microextraction by packed sorbents and large volume injection gas chromatography–mass spectrometry
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Laura Vallecillos, Eva Pocurull, Francesc Borrull
A fully automated method has been developed for the determination of eight macrocyclic musk fragrances in urban wastewater. The procedure includes the enrichment of the analytes by microextraction by packed sorbent (MEPS) followed by large volume injection–gas chromatography–mass spectrometry (LVI–GC–MS). The main factors in the MEPS technique were optimized. For all of the analytes, the highest enrichment factors were achieved when 4mL samples were extracted by using C18 MEPS-sorbent and 50μL of ethyl acetate were used for desorption. The eluate was directly analysed by GC–MS. Detection limits were found to be between 5ngL−1 and 10ngL−1, depending on the target analytes. In addition, under optimized conditions, the method gave good levels of intra-day and inter-day repeatability in wastewater samples with relative standard deviation (RSD) (n =3, 1000ngL−1) less than 5% and 9%, respectively. The applicability of the method was tested with wastewater samples from two influent and effluent urban wastewater treatment plants (WWTPs). The analysis of influent urban wastewater revealed the presence of most of the macrocylic musks at concentrations higher than the method quantification limits (MQLs), being the most abundant analyte ambrettolide at 9.29μgL−1. In addition, the analyses of effluent urban wastewater showed a decrease in the concentrations with macrocyclic musk concentrations of between not detected (n.d.) and 2.26μgL−1 being detected.
Source:Journal of Chromatography A, Volume 1264
Laura Vallecillos, Eva Pocurull, Francesc Borrull
A fully automated method has been developed for the determination of eight macrocyclic musk fragrances in urban wastewater. The procedure includes the enrichment of the analytes by microextraction by packed sorbent (MEPS) followed by large volume injection–gas chromatography–mass spectrometry (LVI–GC–MS). The main factors in the MEPS technique were optimized. For all of the analytes, the highest enrichment factors were achieved when 4mL samples were extracted by using C18 MEPS-sorbent and 50μL of ethyl acetate were used for desorption. The eluate was directly analysed by GC–MS. Detection limits were found to be between 5ngL−1 and 10ngL−1, depending on the target analytes. In addition, under optimized conditions, the method gave good levels of intra-day and inter-day repeatability in wastewater samples with relative standard deviation (RSD) (n =3, 1000ngL−1) less than 5% and 9%, respectively. The applicability of the method was tested with wastewater samples from two influent and effluent urban wastewater treatment plants (WWTPs). The analysis of influent urban wastewater revealed the presence of most of the macrocylic musks at concentrations higher than the method quantification limits (MQLs), being the most abundant analyte ambrettolide at 9.29μgL−1. In addition, the analyses of effluent urban wastewater showed a decrease in the concentrations with macrocyclic musk concentrations of between not detected (n.d.) and 2.26μgL−1 being detected.
Highlights
► The work was focused on the determination of 8 macrocyclic musk in urban wastewater. ► MEPS instead of SPE have been used to preconcentrate the target analytes. ► Large volume injection permitted the automation of the whole analytical method. ► Method detection and quantification limits were found in the low ngL−1. ► Good values of intra-day and inter-day repeatabilities have been obtained.Linear solvation energy relationships as classifiers in non-target analysis – A gas chromatographic approach
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Nadin Ulrich, Jana Mühlenberg, Heiko Retzbach, Gerrit Schüürmann, Werner Brack
Linear solvation energy relationships (LSERs) are applied as classifiers to predict the logarithmic retention factors log k from the structures of candidate compounds in non-target analysis. By comparison of the predicted value with the experimentally determined log k, progressive exclusion of candidates is done. The approach is based on the determination of stationary phase parameters to describe ten different gas chromatographic columns under four isothermal conditions. To demonstrate retention prediction and the application of the classifier model, twelve compounds with the molecular formula C12H10O2 were selected, while experimental log k values were compared to the predicted values and exclusion of potential candidate compounds was performed. The analytical power of the approach was demonstrated on the basis of experimentally determined compound descriptors achieved from gas chromatographic measurements. The prediction got less accurate when calculated compound descriptors were employed. For the time being insufficient precision in estimating the descriptors limits the possibility to exclude candidate compounds in non-target analysis. It is expected that new approaches to estimate compound descriptors, will improve this situation. At present, the insufficient accuracy of descriptor estimates can be dealt with larger prognosis intervals. Furthermore, the combination of two stationary phases with corresponding retention prediction further advanced the exclusion of potential candidates. The most appropriate pair of stationary phases was selected by the application of four different orthogonal strategies. In addition, the classifier was applied for a validation set with different molecular composition, where column selection was considered on the basis of the differences in the compound descriptors of the corresponding candidate compounds.
Source:Journal of Chromatography A, Volume 1264
Nadin Ulrich, Jana Mühlenberg, Heiko Retzbach, Gerrit Schüürmann, Werner Brack
Linear solvation energy relationships (LSERs) are applied as classifiers to predict the logarithmic retention factors log k from the structures of candidate compounds in non-target analysis. By comparison of the predicted value with the experimentally determined log k, progressive exclusion of candidates is done. The approach is based on the determination of stationary phase parameters to describe ten different gas chromatographic columns under four isothermal conditions. To demonstrate retention prediction and the application of the classifier model, twelve compounds with the molecular formula C12H10O2 were selected, while experimental log k values were compared to the predicted values and exclusion of potential candidate compounds was performed. The analytical power of the approach was demonstrated on the basis of experimentally determined compound descriptors achieved from gas chromatographic measurements. The prediction got less accurate when calculated compound descriptors were employed. For the time being insufficient precision in estimating the descriptors limits the possibility to exclude candidate compounds in non-target analysis. It is expected that new approaches to estimate compound descriptors, will improve this situation. At present, the insufficient accuracy of descriptor estimates can be dealt with larger prognosis intervals. Furthermore, the combination of two stationary phases with corresponding retention prediction further advanced the exclusion of potential candidates. The most appropriate pair of stationary phases was selected by the application of four different orthogonal strategies. In addition, the classifier was applied for a validation set with different molecular composition, where column selection was considered on the basis of the differences in the compound descriptors of the corresponding candidate compounds.
Highlights
► Retention prediction by LSER models on 10 GC columns and 4 temperatures. ► Comparison of prediction performance with calculated and experimental descriptors. ► Demonstration of application as classifier in non-target analysis with set of isomers. ► Validation for candidate compounds with different molecular composition. ► Column selection for compound classes to optimize candidate exclusions.A novel derivatization approach for determination of ketamine in urine and plasma by gas chromatography–mass spectrometry
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Kaoqi Lian, Pingping Zhang, Lingmei Niu, Siyuan Bi, Shipeng Liu, Lingling Jiang, Weijun Kang
A new method was developed for determination of ketamine (KT) in urine and plasma samples by derivatization and gas chromatography–mass spectrometry. In this article, KT was first derivatized with sodium nitrite to volatile N-nitrosamines under acidic condition. Then the derivative had been identified by the mass spectra. The derivatization conditions including the amount of hydrochloric acid, the amount of sodium nitrite, reaction temperature, reaction time and the extraction reagents were optimized. Calibration curves were linear in the range of 0.04–20μgmL−1 for KT, and the limit of detection (LOD) and limit of quantitation (LOQ) were 0.01μgmL−1 and 0.04μgmL−1, respectively. The results of recovery indicated that the method had good precision and reproducibility. Compared with existing derivatization methods, this method provided a rapid, convenient, effective and low-cost way for gas chromatography method of KT quantification.
Source:Journal of Chromatography A, Volume 1264
Kaoqi Lian, Pingping Zhang, Lingmei Niu, Siyuan Bi, Shipeng Liu, Lingling Jiang, Weijun Kang
A new method was developed for determination of ketamine (KT) in urine and plasma samples by derivatization and gas chromatography–mass spectrometry. In this article, KT was first derivatized with sodium nitrite to volatile N-nitrosamines under acidic condition. Then the derivative had been identified by the mass spectra. The derivatization conditions including the amount of hydrochloric acid, the amount of sodium nitrite, reaction temperature, reaction time and the extraction reagents were optimized. Calibration curves were linear in the range of 0.04–20μgmL−1 for KT, and the limit of detection (LOD) and limit of quantitation (LOQ) were 0.01μgmL−1 and 0.04μgmL−1, respectively. The results of recovery indicated that the method had good precision and reproducibility. Compared with existing derivatization methods, this method provided a rapid, convenient, effective and low-cost way for gas chromatography method of KT quantification.
Highlights
► A new derivatization method for determination of KT by GC–MS has been developed. ► Comparison with other methods, the method is simple, rapid, effective, and low-cost. ► The recovery and precision of the method are highly satisfactory. ► The method will provide a new strategy for the detection of secondary amine drugs.A sensitive and selective method for the determination of selected pesticides in fruit by gas chromatography/mass spectrometry with negative chemical ionization
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
N. Belmonte Valles, M. Retamal, M. Mezcua, A.R. Fernández-Alba
Multiresidue methods (MRMs) for pesticides residues determination in fruit and vegetables, based on GC–MS, are mainly performed in electron impact ionization mode. However an important group of them provide much better response working in negative chemical ionization mode due to the elimination of a high percentage of background signal. Considering that a selective and sensitive method has been developed for the determination of multiclass pesticide residues in different commodities by GC–MS with a triple stage quadrupole analyzer (GC–TSQ–MS); the pesticide signal has been optimized in MS–MS whilst working in negative chemical ionization mode using methane as the reagent gas. The proposed method was fully validated for 53 compounds in tomato, apple and orange matrices. The obtained limits of determination were lower than 0.1μg/kg for more than 50% of the pesticides studied, and lower than 1μg/kg for all pesticides studied, except for cypermethrin, boscalid, bifenthrin and deltamethrin. Linearity was studied in the 0.5–50μg/kg range and a linear response was obtained for all pesticides in all matrices. Recoveries were evaluated at two different levels (1 and 50μg/kg) and recoveries were ranged between 70 and 120% in tomato, apple and orange, except in the cases of chlorfenapyr, ofurace, chlozolinate, chlorothalonil, tolylfluanid and dichlofluanid with recovery values close to 60% at 1μg/kg fortification levels. Repetitivity was evaluated and the relative standard deviation (RSD%) was lower than 10% in all cases. The developed method was employed in the analysis of real samples intended for baby food and the obtained results showed that 50% of the samples were positive for different pesticide residues. The concentration range detected was between 5 and 100μg/kg. The positive detection of OCs was particularly noticeable; these included chlorothalonil, fenhexamide, clorpyrifos and lambda cyhalothrin, which are very persistent and toxic with low acute reference dose. Endosulfan sulfate, which is not approved, was detected at a low concentration.
Source:Journal of Chromatography A, Volume 1264
N. Belmonte Valles, M. Retamal, M. Mezcua, A.R. Fernández-Alba
Multiresidue methods (MRMs) for pesticides residues determination in fruit and vegetables, based on GC–MS, are mainly performed in electron impact ionization mode. However an important group of them provide much better response working in negative chemical ionization mode due to the elimination of a high percentage of background signal. Considering that a selective and sensitive method has been developed for the determination of multiclass pesticide residues in different commodities by GC–MS with a triple stage quadrupole analyzer (GC–TSQ–MS); the pesticide signal has been optimized in MS–MS whilst working in negative chemical ionization mode using methane as the reagent gas. The proposed method was fully validated for 53 compounds in tomato, apple and orange matrices. The obtained limits of determination were lower than 0.1μg/kg for more than 50% of the pesticides studied, and lower than 1μg/kg for all pesticides studied, except for cypermethrin, boscalid, bifenthrin and deltamethrin. Linearity was studied in the 0.5–50μg/kg range and a linear response was obtained for all pesticides in all matrices. Recoveries were evaluated at two different levels (1 and 50μg/kg) and recoveries were ranged between 70 and 120% in tomato, apple and orange, except in the cases of chlorfenapyr, ofurace, chlozolinate, chlorothalonil, tolylfluanid and dichlofluanid with recovery values close to 60% at 1μg/kg fortification levels. Repetitivity was evaluated and the relative standard deviation (RSD%) was lower than 10% in all cases. The developed method was employed in the analysis of real samples intended for baby food and the obtained results showed that 50% of the samples were positive for different pesticide residues. The concentration range detected was between 5 and 100μg/kg. The positive detection of OCs was particularly noticeable; these included chlorothalonil, fenhexamide, clorpyrifos and lambda cyhalothrin, which are very persistent and toxic with low acute reference dose. Endosulfan sulfate, which is not approved, was detected at a low concentration.
Highlights
► Selective and sensitive method for determination of multi-class pesticides. ► GC–MS with a triple stage quadrupole analyzer (GC–TSQ–MS). ► Working in negative chemical ionization mode using methane as reactive gas. ► Analysis of real samples intended for baby food. ► Extraction method: liquid extraction using ethyl acetate as extraction solvent.Imprinted polymers for chiral resolution of (±)-ephedrine, 4: Packed column supercritical fluid chromatography using molecularly imprinted chiral stationary phases
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Richard J. Ansell, Janice K.L. Kuah, Dongyao Wang, Clare E. Jackson, Keith D. Bartle, Anthony A. Clifford
(−)-Ephedrine-molecularly imprinted polymers (MIPs) have been successfully used as stationary phases in supercritical fluid chromatography for the separation of (±)-ephedrine enantiomers. This approach combines the simple preparation and predictable elution order of MIP stationary phases with the superior mobile phase diffusivity and low viscosity of supercritical fluid mobile phases. The optimised mobile phase comprised supercritical carbon dioxide with a modifier consisting of MeOH/isopropylamine/H2O 93:5:2 (v/v/v). In many cases, better resolution separations were observed compared to when liquid mobile phases were used, and better separations achieved at high sample loads, although interestingly the MIPs which work best in SFC are different from the MIPs that work best in HPLC with an amine modifier. The MIP stationary phases were stable under the conditions employed and the chromatography was reproducible. This work opens the door to exploiting MIP stationary phases in preparative SFC.
Source:Journal of Chromatography A, Volume 1264
Richard J. Ansell, Janice K.L. Kuah, Dongyao Wang, Clare E. Jackson, Keith D. Bartle, Anthony A. Clifford
(−)-Ephedrine-molecularly imprinted polymers (MIPs) have been successfully used as stationary phases in supercritical fluid chromatography for the separation of (±)-ephedrine enantiomers. This approach combines the simple preparation and predictable elution order of MIP stationary phases with the superior mobile phase diffusivity and low viscosity of supercritical fluid mobile phases. The optimised mobile phase comprised supercritical carbon dioxide with a modifier consisting of MeOH/isopropylamine/H2O 93:5:2 (v/v/v). In many cases, better resolution separations were observed compared to when liquid mobile phases were used, and better separations achieved at high sample loads, although interestingly the MIPs which work best in SFC are different from the MIPs that work best in HPLC with an amine modifier. The MIP stationary phases were stable under the conditions employed and the chromatography was reproducible. This work opens the door to exploiting MIP stationary phases in preparative SFC.
Highlights
► MIPs successfully used as stationary phases in separation of (±)-ephedrine by SFC. ► MIPs are stable under the conditions used and the chromatography is reproducible. ► Better separations achieved with the best MIP in SFC than with any of them in HPLC. ► The mobile phase is carbon dioxide with a modifier of methanol/isopropylamine/water.Processes involved in sweeping under inhomogeneous electric field conditions as sample enrichment procedure in micellar electrokinetic chromatography
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Mohamed El-Awady, Carolin Huhn, Ute Pyell
Sweeping under inhomogeneous electric field conditions has been described as a process that includes stacking or destacking of the micelles when entering the sample zone, sweeping of analytes by the stacked or destacked micelles, and destacking or stacking of the swept analyte zone. However, there is ongoing debate that not only the retention factor of the analyte but also the electric conductivity of the sample solution or the concentration of an added salt can have an impact on the enrichment efficiency. Revisiting the equations describing sweeping, a factor θ (phase ratio shift factor) is defined to quantitatively describe the change of the retention factor between the sample and separation zones. The influence of the sample matrix composition on the experimentally obtained sweeping efficiency is studied with SDS as pseudostationary phase taking parabens, benzamide and anilines as model analytes. To this end, a robust and reliable method for the assessment of the sweeping efficiency is developed. The values obtained via this method are very precise and agree well with theoretically predicted ones. The results obtained for varied buffer concentration and varied concentration of NaCl in the sample solution show that under the conditions of our experimental study, the approximation of assuming θ to be equal to the reciprocal value of the field strength enhancement factor γ is valid. Accordingly, the sweeping efficiency for neutral analytes is independent of the electric conductivity of the sample matrix. It is also shown that under specific conditions unexpectedly high enrichment factors are obtained which are ascribed to the focusing of neutral analytes by micellar transient isotachophoresis (mtITP). The results obtained in this study can be used as a guide for better understanding of the sweeping process and the factors affecting the sweeping efficiency in micellar electrokinetic chromatography (MEKC).
Source:Journal of Chromatography A, Volume 1264
Mohamed El-Awady, Carolin Huhn, Ute Pyell
Sweeping under inhomogeneous electric field conditions has been described as a process that includes stacking or destacking of the micelles when entering the sample zone, sweeping of analytes by the stacked or destacked micelles, and destacking or stacking of the swept analyte zone. However, there is ongoing debate that not only the retention factor of the analyte but also the electric conductivity of the sample solution or the concentration of an added salt can have an impact on the enrichment efficiency. Revisiting the equations describing sweeping, a factor θ (phase ratio shift factor) is defined to quantitatively describe the change of the retention factor between the sample and separation zones. The influence of the sample matrix composition on the experimentally obtained sweeping efficiency is studied with SDS as pseudostationary phase taking parabens, benzamide and anilines as model analytes. To this end, a robust and reliable method for the assessment of the sweeping efficiency is developed. The values obtained via this method are very precise and agree well with theoretically predicted ones. The results obtained for varied buffer concentration and varied concentration of NaCl in the sample solution show that under the conditions of our experimental study, the approximation of assuming θ to be equal to the reciprocal value of the field strength enhancement factor γ is valid. Accordingly, the sweeping efficiency for neutral analytes is independent of the electric conductivity of the sample matrix. It is also shown that under specific conditions unexpectedly high enrichment factors are obtained which are ascribed to the focusing of neutral analytes by micellar transient isotachophoresis (mtITP). The results obtained in this study can be used as a guide for better understanding of the sweeping process and the factors affecting the sweeping efficiency in micellar electrokinetic chromatography (MEKC).
Highlights
► A new reliable method for the determination of sweeping efficiency is developed. ► Sweeping under inhomogeneous electric field condition is a complex multistep process. ► Sweeping efficiency is independent of the electric conductivity of the sample matrix. ► Focusing by micellar transient isotachophoresis is suggested under specific cases. ► Better understanding of the sweeping process and related phenomena is achieved.Molecularly imprinted nanoparticles with nontailing peaks in capillary electrochromatography
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
Xiao Liu, Ze-Hui Wei, Yan-Ping Huang, Jin-Rong Yang, Zhao-Sheng Liu
The combination of microparticles of molecularly imprinted polymers (MIPs) with partial filling capillary electrochromatography (CEC) has previously been demonstrated for the enantiomer separation. In this paper, precipitation polymerization was used to prepare d-zopiclone imprinted nanoparticles (50–80nm) by a strategy of the dilution of pre-polymerization mixtures. The influence of some important parameters on the preparation of MIPs nanoparticles, including template to monomer ratio, type and amount of cross-linking monomer, and functional monomer composition ratio were investigated. In addition, the effect of separation condition, e.g., organic modifier content, pH value and salt concentration of buffer, on the electrochromatographic behavior of the MIP nanoparticles were studied. In spite of lower selectivity factor (1.11), high column performance (theoretical plates 41,400) of template was obtained and the resolution of enantiomers separation was 4.75 under the optimized conditions. Compared to the previously reported MIP microparticles, the MIP nanoparticles showed good peak symmetry and an ability of high speed separation (<15min) in CEC mode.
Source:Journal of Chromatography A, Volume 1264
Xiao Liu, Ze-Hui Wei, Yan-Ping Huang, Jin-Rong Yang, Zhao-Sheng Liu
The combination of microparticles of molecularly imprinted polymers (MIPs) with partial filling capillary electrochromatography (CEC) has previously been demonstrated for the enantiomer separation. In this paper, precipitation polymerization was used to prepare d-zopiclone imprinted nanoparticles (50–80nm) by a strategy of the dilution of pre-polymerization mixtures. The influence of some important parameters on the preparation of MIPs nanoparticles, including template to monomer ratio, type and amount of cross-linking monomer, and functional monomer composition ratio were investigated. In addition, the effect of separation condition, e.g., organic modifier content, pH value and salt concentration of buffer, on the electrochromatographic behavior of the MIP nanoparticles were studied. In spite of lower selectivity factor (1.11), high column performance (theoretical plates 41,400) of template was obtained and the resolution of enantiomers separation was 4.75 under the optimized conditions. Compared to the previously reported MIP microparticles, the MIP nanoparticles showed good peak symmetry and an ability of high speed separation (<15min) in CEC mode.
Highlights
► Molecularly imprinted nanoparticles with size of 50–80nm were prepared with zopiclone as template. ► Baseline separation of enantiomer separation can be achieved with imprinted nanoparticles in CEC mode. ► Polymerization factors on the imprinting effect of MIP nanoparticles were investigated. ► Imprinted nanoparticles showed higher efficiency for template with good peak symmetry.The role of harmonized, gas and liquid chromatography mass spectrometry in the discovery of the neolignan balanophonin in the fruit wall of Cirsium vulgare
22 October 2012,
08:56:27
Publication year:
2012
Source:Journal of Chromatography A, Volume 1264
I. Boldizsár, M. Kraszni, F. Tóth, G. Tóth, A. Sólyomváry, B. Noszál, Gy. Záray, I. Molnár-Perl
In order to identify and quantify fruit-lignans of Cirsium vulgare – authors introduced a special analysis system: with particular attention to the lignans enrichment/separation course. These synchronized, germination and enzymatic hydrolysis processes were followed by complementary gas and liquid chromatography, coupled with special mass selective detections (GC–MS, LC–MS/MS, LC–TOF/MS) and confirmed by nuclear magnetic resonance (NMR) spectroscopy. Mass fragmentations and NMR evidences, proved that the two main medicinal lignan constituents of the fruits of Cirsium vulgare are the neolignan-type, free balanophonin and the butyrolactone-type tracheloside. As novelty to the field, these two lignans of different chemical structures could be quantitatively extracted, separately from each others, without impurities. Balanophonin and tracheloside do accumulate in the fruits of C. vulgare, separately: balanophonin was found, in enormous high concentrations, in the fruit wall (23.2–24.9mg/g), while in embryo part tracheloside was determined (20.3mg/g), exclusively. Consequently, the optimum source of balanophonin proved to be the fruit wall, while tracheloside, – providing trachelogenin upon enzymatic hydrolysis, – could be obtained from the embryo parts of fruits. As further novelties of the study balanophonin was identified and quantified at the first time with on-line chromatographic technique, in free form, without authentic standard compound.
Source:Journal of Chromatography A, Volume 1264
I. Boldizsár, M. Kraszni, F. Tóth, G. Tóth, A. Sólyomváry, B. Noszál, Gy. Záray, I. Molnár-Perl
In order to identify and quantify fruit-lignans of Cirsium vulgare – authors introduced a special analysis system: with particular attention to the lignans enrichment/separation course. These synchronized, germination and enzymatic hydrolysis processes were followed by complementary gas and liquid chromatography, coupled with special mass selective detections (GC–MS, LC–MS/MS, LC–TOF/MS) and confirmed by nuclear magnetic resonance (NMR) spectroscopy. Mass fragmentations and NMR evidences, proved that the two main medicinal lignan constituents of the fruits of Cirsium vulgare are the neolignan-type, free balanophonin and the butyrolactone-type tracheloside. As novelty to the field, these two lignans of different chemical structures could be quantitatively extracted, separately from each others, without impurities. Balanophonin and tracheloside do accumulate in the fruits of C. vulgare, separately: balanophonin was found, in enormous high concentrations, in the fruit wall (23.2–24.9mg/g), while in embryo part tracheloside was determined (20.3mg/g), exclusively. Consequently, the optimum source of balanophonin proved to be the fruit wall, while tracheloside, – providing trachelogenin upon enzymatic hydrolysis, – could be obtained from the embryo parts of fruits. As further novelties of the study balanophonin was identified and quantified at the first time with on-line chromatographic technique, in free form, without authentic standard compound.
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