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Ultrahigh performance liquid chromatographic analysis and magnetic preconcentration of polycyclic aromatic hydrocarbons by Fe3O4-doped polymeric nanoparticles
25 June 2012,
09:31:04
Publication year:
2012
Source:Journal of Chromatography A, Volume 1247
Xicui Zhang, Shunping Xie, Man Chin Paau, Baozhan Zheng, Hongyan Yuan, Dan Xiao, Martin M.F. Choi
This paper reports the synthesis of hydrophilic–hydrophobic magnetic Fe3O4-doped polymeric nanoparticles (MPNP) and its application for preconcentration of polycyclic aromatic hydrocarbons (PAHs) in environmental water samples for ultrahigh performance liquid chromatographic (UHPLC) analysis. The MPNP were prepared from highly charged poly(styrene-divinylbenzene-co-4-vinylbenzenesulfonic acid sodium salt) nanoparticles impregnated with Fe2+ via the electrostatic attraction and by microwave heating. The MPNP are relatively uniform in size with an average diameter of 50nm and have a magnetic saturation value of 24.5emu/g. The hydrophilic–hydrophobic MPNP could easily disperse in water. The phenyl moieties of MPNP assist the adsorption of PAHs via both hydrophobic and π–π interactions. The separation of the PAHs-adsorbed MPNP from water could be easily achieved by a permanent magnet and the adsorbed PAHs were back extracted into acetonitrile for UHPLC analysis. The UHPLC separation of PAHs is very quick and could be achieved within 1.6min. Factors affecting the extraction and desorption were investigated in detail. Under the optimum experimental conditions, the recoveries of various PAHs including acenaphthylene, anthracene, fluoranthene, fluorene, phenanthrene, and pyrene in water samples at three different concentrations are 75.7–102.9, 77.8–101.2, 86.3–100.7, 88.5–99.7, 92.0–106.4, and 81.6–98.5%, respectively. The recovery SDs are 0.30–8.20% and the instrumental limits of detection are 10.83–18.53nM. The proposed technique combining hydrophobic extraction and magnetic separation coupled with UHPLC could provide a fast, convenient and sensitive method for the determination of PAHs in water samples.
Source:Journal of Chromatography A, Volume 1247
Xicui Zhang, Shunping Xie, Man Chin Paau, Baozhan Zheng, Hongyan Yuan, Dan Xiao, Martin M.F. Choi
This paper reports the synthesis of hydrophilic–hydrophobic magnetic Fe3O4-doped polymeric nanoparticles (MPNP) and its application for preconcentration of polycyclic aromatic hydrocarbons (PAHs) in environmental water samples for ultrahigh performance liquid chromatographic (UHPLC) analysis. The MPNP were prepared from highly charged poly(styrene-divinylbenzene-co-4-vinylbenzenesulfonic acid sodium salt) nanoparticles impregnated with Fe2+ via the electrostatic attraction and by microwave heating. The MPNP are relatively uniform in size with an average diameter of 50nm and have a magnetic saturation value of 24.5emu/g. The hydrophilic–hydrophobic MPNP could easily disperse in water. The phenyl moieties of MPNP assist the adsorption of PAHs via both hydrophobic and π–π interactions. The separation of the PAHs-adsorbed MPNP from water could be easily achieved by a permanent magnet and the adsorbed PAHs were back extracted into acetonitrile for UHPLC analysis. The UHPLC separation of PAHs is very quick and could be achieved within 1.6min. Factors affecting the extraction and desorption were investigated in detail. Under the optimum experimental conditions, the recoveries of various PAHs including acenaphthylene, anthracene, fluoranthene, fluorene, phenanthrene, and pyrene in water samples at three different concentrations are 75.7–102.9, 77.8–101.2, 86.3–100.7, 88.5–99.7, 92.0–106.4, and 81.6–98.5%, respectively. The recovery SDs are 0.30–8.20% and the instrumental limits of detection are 10.83–18.53nM. The proposed technique combining hydrophobic extraction and magnetic separation coupled with UHPLC could provide a fast, convenient and sensitive method for the determination of PAHs in water samples.
Highlights
► Hydrophilic–hydrophobic magnetic Fe3O4-doped polymeric nanoparticles (MPNP) are successfully synthesized by a simple microwave-heating method. ► These MPNP disperse easily in water and are very effective in extracting polycyclic aromatic hydrocarbons (PAHs) from aqueous solution. ► The extraction time is fast and the required amount of MPNP for preconcentration of PAHs is less and cost-effective. ► UHPLC analysis of PAHs is fast and can be done in less than 1.6min.Detection of seven pesticides in cucumbers using hollow fibre-based liquid-phase microextraction and ultra-high pressure liquid chromatography coupled to tandem mass spectrometry
25 June 2012,
09:31:04
Publication year:
2012
Source:Journal of Chromatography A, Volume 1247
Jianfeng Wang, Zhenxia Du, Wenlian Yu, Shuping Qu
A liquid-phase microextraction (LPME) methodology based on the use of porous polyvinylidene fluoride (PVDF) hollow fibres was developed for extracting seven pesticides from cucumbers. The seven pesticides include propoxur, carbofuran, atrazine, cyanatryn, metolachlor, prometryn and tebuconazole. The PVDF hollow fibre provides higher extraction efficiency due to its higher porosity and better solvent compatibility. A new desorption methodology was developed since some pesticides were absorbed by the wall pore of the PVDF. Ultra-high pressure liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS) was used for pesticide analysis. In order to obtain high recoveries and enrichment factors of the analytes, several parameters such as method of sealing, acceptor phase (organic solvents), stirring speed, extraction time, salting out effect, desorption mode and time were optimized. A fast, simple method for closing fibre ends was practiced by using mechanical crimping. Pesticides were extracted from the sample to the organic solvent and then desorbed in a mixture of methanol:water (1:1 v/v) prior to chromatographic analysis. Limits of detection (LOD) for the multi-reaction-monitoring (MRM) mode of the method varies from 0.01 to 0.31μg/kg with optimized sample preparation. Calibration curves are linear with R 2 ≥0.991. Enrichment factor of the hollow fibre LPME ranges from 100 to 147. Matrix effect has been considered and is in the range of 76–122%. The relative recoveries from cucumber samples are between 63% and 119% with the relative standard deviation (RSD, n =6) lower than 20%.
Source:Journal of Chromatography A, Volume 1247
Jianfeng Wang, Zhenxia Du, Wenlian Yu, Shuping Qu
A liquid-phase microextraction (LPME) methodology based on the use of porous polyvinylidene fluoride (PVDF) hollow fibres was developed for extracting seven pesticides from cucumbers. The seven pesticides include propoxur, carbofuran, atrazine, cyanatryn, metolachlor, prometryn and tebuconazole. The PVDF hollow fibre provides higher extraction efficiency due to its higher porosity and better solvent compatibility. A new desorption methodology was developed since some pesticides were absorbed by the wall pore of the PVDF. Ultra-high pressure liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS) was used for pesticide analysis. In order to obtain high recoveries and enrichment factors of the analytes, several parameters such as method of sealing, acceptor phase (organic solvents), stirring speed, extraction time, salting out effect, desorption mode and time were optimized. A fast, simple method for closing fibre ends was practiced by using mechanical crimping. Pesticides were extracted from the sample to the organic solvent and then desorbed in a mixture of methanol:water (1:1 v/v) prior to chromatographic analysis. Limits of detection (LOD) for the multi-reaction-monitoring (MRM) mode of the method varies from 0.01 to 0.31μg/kg with optimized sample preparation. Calibration curves are linear with R 2 ≥0.991. Enrichment factor of the hollow fibre LPME ranges from 100 to 147. Matrix effect has been considered and is in the range of 76–122%. The relative recoveries from cucumber samples are between 63% and 119% with the relative standard deviation (RSD, n =6) lower than 20%.
Highlights
► A porous PVDF hollow fibre LPME was used for extracting pesticides from cucumbers. ► A fast, simple method of the fibre seal was practiced by using insulated terminal. ► Desorption mode changed and pesticides in fibre were desorbed after extraction. ► The fibre with large membrane porosity can be applied to pesticide extraction.Strong ion exchange in centrifugal partition extraction (SIX-CPE): Effect of partition cell design and dimensions on purification process efficiency
25 June 2012,
09:31:04
Publication year:
2012
Source:Journal of Chromatography A, Volume 1247
Mahmoud Hamzaoui, Jane Hubert, Romain Reynaud, Luc Marchal, Alain Foucault, Jean-Hugues Renault
The aim of this article was to evaluate the influence of the column design of a hydrostatic support-free liquid–liquid chromatography device on the process efficiency when the strong ion-exchange (SIX) development mode is used. The purification of p-hydroxybenzylglucosinolate (sinalbin) from a crude aqueous extract of white mustard seeds (Sinapis alba L.) was achieved on two types of devices: a centrifugal partition chromatograph (CPC) and a centrifugal partition extractor (CPE). They differ in the number, volume and geometry of their partition cells. The SIX-CPE process was evaluated in terms of productivity and sinalbin purification capability as compared to previously optimized SIX-CPC protocols that were carried out on columns of 200mL and 5700mL inner volume, respectively. The objective was to determine whether the decrease in partition cell number, the increase in their volume and the use of a “twin cell” design would induce a significant increase in productivity by applying higher mobile phase flow rate while maintaining a constant separation quality. 4.6g of sinalbin (92% recovery) were isolated from 25g of a crude white mustard seed extract, in only 32min and with a purity of 94.7%, thus corresponding to a productivity of 28g per hour and per liter of column volume ( g/h/L V c ) . Therefore, the SIX-CPE process demonstrates promising industrial technology transfer perspectives for the large-scale isolation of ionized natural products.
Source:Journal of Chromatography A, Volume 1247
Mahmoud Hamzaoui, Jane Hubert, Romain Reynaud, Luc Marchal, Alain Foucault, Jean-Hugues Renault
The aim of this article was to evaluate the influence of the column design of a hydrostatic support-free liquid–liquid chromatography device on the process efficiency when the strong ion-exchange (SIX) development mode is used. The purification of p-hydroxybenzylglucosinolate (sinalbin) from a crude aqueous extract of white mustard seeds (Sinapis alba L.) was achieved on two types of devices: a centrifugal partition chromatograph (CPC) and a centrifugal partition extractor (CPE). They differ in the number, volume and geometry of their partition cells. The SIX-CPE process was evaluated in terms of productivity and sinalbin purification capability as compared to previously optimized SIX-CPC protocols that were carried out on columns of 200mL and 5700mL inner volume, respectively. The objective was to determine whether the decrease in partition cell number, the increase in their volume and the use of a “twin cell” design would induce a significant increase in productivity by applying higher mobile phase flow rate while maintaining a constant separation quality. 4.6g of sinalbin (92% recovery) were isolated from 25g of a crude white mustard seed extract, in only 32min and with a purity of 94.7%, thus corresponding to a productivity of 28g per hour and per liter of column volume ( g/h/L V c ) . Therefore, the SIX-CPE process demonstrates promising industrial technology transfer perspectives for the large-scale isolation of ionized natural products.
Highlights
► An IP-CPE method was developed for the purification of sinalbin from white mustard seeds. ► IP-CPE process was compared with CPC columns of 200mL and 5700mL capacity. ► IP-CPE offers promising perspectives for the large-scale isolation of natural ionized products.Dispersive liquid–liquid microextraction using a low density extraction solvent for the determination of 17 N-methylcarbamates by micellar electrokinetic chromatography–electrospray–mass spectrometry employing a volatile surfactant
25 June 2012,
09:31:04
Publication year:
2012
Source:Journal of Chromatography A, Volume 1247
David Moreno-González, Laura Gámiz-Gracia, Juan M. Bosque-Sendra, Ana M. García-Campaña
A new analytical method based on micellar electrokinetic chromatography tandem mass spectrometry (MEKC–ESI–MS/MS) employing a MS friendly surfactant (ammonium perfluorooctanoate) is proposed and validated for the identification and simultaneous quantification of 17 N-methylcarbamate pesticides in environmental and drinking water samples. MS/MS detection using an ion trap as analyzer operating in the multiple reaction monitoring mode was used. Different parameters were optimized in order to obtain an adequate CE separation combined with the highest sensitivity in MS/MS. Dispersive liquid–liquid microextraction (DLLME) using a low-density extraction solvent has been proposed for extraction, obtaining a preconcentration factor of 10. Under optimum conditions, recoveries for fortified samples ranged from 83% to 101%, with relative standard deviations lower than 8%. The limits of detection ranged from 1 to 144ngl−1, demonstrating the sensitivity and applicability of this fast, simple, and environmentally friendly method.
Source:Journal of Chromatography A, Volume 1247
David Moreno-González, Laura Gámiz-Gracia, Juan M. Bosque-Sendra, Ana M. García-Campaña
A new analytical method based on micellar electrokinetic chromatography tandem mass spectrometry (MEKC–ESI–MS/MS) employing a MS friendly surfactant (ammonium perfluorooctanoate) is proposed and validated for the identification and simultaneous quantification of 17 N-methylcarbamate pesticides in environmental and drinking water samples. MS/MS detection using an ion trap as analyzer operating in the multiple reaction monitoring mode was used. Different parameters were optimized in order to obtain an adequate CE separation combined with the highest sensitivity in MS/MS. Dispersive liquid–liquid microextraction (DLLME) using a low-density extraction solvent has been proposed for extraction, obtaining a preconcentration factor of 10. Under optimum conditions, recoveries for fortified samples ranged from 83% to 101%, with relative standard deviations lower than 8%. The limits of detection ranged from 1 to 144ngl−1, demonstrating the sensitivity and applicability of this fast, simple, and environmentally friendly method.
Highlights
► 17 N-methylcarbamate pesticides in water samples by MEKC–ESI–MS/MS. ► Use of a volatile surfactant to match the micellar mode in CE with the MS detection. ► Dispersive liquid–liquid microextraction procedure for preconcentration and clean up. ► Validation of the method in three different water samples. ► LODs between 1.4 and 143.7ngl−1 with satisfactory precision.A novel method for high preconcentration of ultra trace amounts of B1, B2, G1 and G2 aflatoxins in edible oils by dispersive liquid–liquid microextraction after immunoaffinity column clean-up
25 June 2012,
09:31:04
Publication year:
2012
Source:Journal of Chromatography A, Volume 1247
Daryoush Afzali, Maryam Ghanbarian, Ali Mostafavi, Tayebeh Shamspur, Sima Ghaseminezhad
In the present study, a new approach which uses immunoaffinity column clean-up combined with dispersive liquid–liquid microextraction (DLLME) is proposed for the preconcentration of ultra trace amounts of aflatoxins (B1, B2, G1 and G2). The aflatoxins are then determined using a high-performance liquid chromatography coupled with fluorescent detector. Samples are extracted by immunoaffinity column (IAC) clean-up, and their eluents are used as dispersants of the subsequent DLLME, for further enrichment of aflatoxins. Various parameters (the type of elution solvent, the type and volume of extraction solvent and disperser solvent, extraction time, and centrifugation time) that affect the efficiency of the two steps are optimized. Under the optimum conditions (extraction solvent: 120μL of chloroform, disperser solvent: 500μL of acetonitrile, sample pH: 7.4, centrifugation time: 3min), the calibration for B1, B2, G1 and G2 was found to be linear with coefficient of estimation (R 2) of 0.9994, 0.9976, 0.9989, 0.9973 respectively and the limit of detection (LOD) was between 1.1×10−4 to 5.3×10−3 ngmL−1 (3σ b/m, n =9). The recoveries at the two spiked levels ranged from 96.0 to 110.0% and the relative standard deviation (RSD) was less than 7.8% (n =9). The results show that dispersive liquid–liquid microextraction combined with HPLC is a selective, simple, sensitive, and effective analytical method for the preconcentration and determination of ultra trace amounts of aflatoxins. The proposed method was applied for preconcentration and determination of B1, B2, G1 and G2 aflatoxin in edible oils. Analysis of aflatoxins in FAPAS test material showed that the proposed method has good accuracy.
Source:Journal of Chromatography A, Volume 1247
Daryoush Afzali, Maryam Ghanbarian, Ali Mostafavi, Tayebeh Shamspur, Sima Ghaseminezhad
In the present study, a new approach which uses immunoaffinity column clean-up combined with dispersive liquid–liquid microextraction (DLLME) is proposed for the preconcentration of ultra trace amounts of aflatoxins (B1, B2, G1 and G2). The aflatoxins are then determined using a high-performance liquid chromatography coupled with fluorescent detector. Samples are extracted by immunoaffinity column (IAC) clean-up, and their eluents are used as dispersants of the subsequent DLLME, for further enrichment of aflatoxins. Various parameters (the type of elution solvent, the type and volume of extraction solvent and disperser solvent, extraction time, and centrifugation time) that affect the efficiency of the two steps are optimized. Under the optimum conditions (extraction solvent: 120μL of chloroform, disperser solvent: 500μL of acetonitrile, sample pH: 7.4, centrifugation time: 3min), the calibration for B1, B2, G1 and G2 was found to be linear with coefficient of estimation (R 2) of 0.9994, 0.9976, 0.9989, 0.9973 respectively and the limit of detection (LOD) was between 1.1×10−4 to 5.3×10−3 ngmL−1 (3σ b/m, n =9). The recoveries at the two spiked levels ranged from 96.0 to 110.0% and the relative standard deviation (RSD) was less than 7.8% (n =9). The results show that dispersive liquid–liquid microextraction combined with HPLC is a selective, simple, sensitive, and effective analytical method for the preconcentration and determination of ultra trace amounts of aflatoxins. The proposed method was applied for preconcentration and determination of B1, B2, G1 and G2 aflatoxin in edible oils. Analysis of aflatoxins in FAPAS test material showed that the proposed method has good accuracy.
Highlights
► The aim of this study is to preconcentrate ultra trace amounts of aflatoxins. ► A new approach dispersive liquid–liquid microextraction is proposed for aflatoxins. ► Determination of B1, B2, G1 and G2 aflatoxin in edible oils was done.Preparation and characterization of vinyl-functionalized mesoporous organosilica-coated solid-phase microextraction fiber
25 June 2012,
09:31:04
Publication year:
2012
Source:Journal of Chromatography A, Volume 1247
Fang Zhu, Yongjin Liang, Liaoyuan Xia, Minzhi Rong, Chengyong Su, Rong Lai, Ruiying Li, Gangfeng Ouyang
Vinyl-SBA-15 mesoporous organosilica was synthesized and used as coating material of solid-phase microextraction (SPME) by two coating techniques (direct coating and sol–gel). The synthesized vinyl-SBA-15 organosilica had highly ordered mesoporous structure, good thermal stability and a specific surface area of 688m2 g−1. The fibers prepared by two methods were evaluated by the extraction of non-polar compounds (BTEX, benzene, toluene, ethylbenzene, o-xylene) and polar compounds (phenols). The results showed that the vinyl-SBA-15 fibers prepared by two methods exhibited high thermal stability (310°C for direct-coated and 350°C for sol–gel) and excellent solvent durability in methanol and acetonitrile. The fibers also presented much better extraction performance for both polar compounds (phenols) and non-polar compounds (BTEX), compared to commercial polydimethylsiloxane (PDMS) fiber, as well as wide linear ranges, low detection limits (0.008–0.047μgL−1 for BTEX, sol–gel; 0.15–5.7μgL−1 for phenols, direct-coated), good repeatabilities (RSDs less than 5.4% for BTEX) and satisfying reproducibilities between fibers (RSDs less than 5.8% for BTEX). The self-made fibers were successfully used for the analysis of BTEX and phenols in three aqueous samples including tap water, mineral water and lake water, which demonstrated the applicability of the vinyl-SBA-15 fibers.
Source:Journal of Chromatography A, Volume 1247
Fang Zhu, Yongjin Liang, Liaoyuan Xia, Minzhi Rong, Chengyong Su, Rong Lai, Ruiying Li, Gangfeng Ouyang
Vinyl-SBA-15 mesoporous organosilica was synthesized and used as coating material of solid-phase microextraction (SPME) by two coating techniques (direct coating and sol–gel). The synthesized vinyl-SBA-15 organosilica had highly ordered mesoporous structure, good thermal stability and a specific surface area of 688m2 g−1. The fibers prepared by two methods were evaluated by the extraction of non-polar compounds (BTEX, benzene, toluene, ethylbenzene, o-xylene) and polar compounds (phenols). The results showed that the vinyl-SBA-15 fibers prepared by two methods exhibited high thermal stability (310°C for direct-coated and 350°C for sol–gel) and excellent solvent durability in methanol and acetonitrile. The fibers also presented much better extraction performance for both polar compounds (phenols) and non-polar compounds (BTEX), compared to commercial polydimethylsiloxane (PDMS) fiber, as well as wide linear ranges, low detection limits (0.008–0.047μgL−1 for BTEX, sol–gel; 0.15–5.7μgL−1 for phenols, direct-coated), good repeatabilities (RSDs less than 5.4% for BTEX) and satisfying reproducibilities between fibers (RSDs less than 5.8% for BTEX). The self-made fibers were successfully used for the analysis of BTEX and phenols in three aqueous samples including tap water, mineral water and lake water, which demonstrated the applicability of the vinyl-SBA-15 fibers.
Highlights
► Vinyl-SBA-15 mesoporous organosilica was synthesized and used as SPME fiber coating. ► The vinyl-SBA-15 fibers has high thermal stability and excellent solvent durability. ► The fibers showed better extraction performance than commercial fibers.Zirconia coated stir bar sorptive extraction combined with large volume sample stacking capillary electrophoresis-indirect ultraviolet detection for the determination of chemical warfare agent degradation products in water samples
25 June 2012,
09:31:04
Publication year:
2012
Source:Journal of Chromatography A, Volume 1247
Pingjing Li, Bin Hu, Xiaoyong Li
In this study, a sensitive, selective and reliable analytical method by combining zirconia (ZrO2) coated stir bar sorptive extraction (SBSE) with large volume sample stacking capillary electrophoresis-indirect ultraviolet (LVSS-CE/indirect UV) was developed for the direct analysis of chemical warfare agent degradation products of alkyl alkylphosphonic acids (AAPAs) (including ethyl methylphosphonic acid (EMPA) and pinacolyl methylphosphonate (PMPA)) and methylphosphonic acid (MPA) in environmental waters. ZrO2 coated stir bar was prepared by adhering nanometer-sized ZrO2 particles onto the surface of stir bar with commercial PDMS sol as adhesion agent. Due to the high affinity of ZrO2 to the electronegative phosphonate group, ZrO2 coated stir bars could selectively extract the strongly polar AAPAs and MPA. After systematically optimizing the extraction conditions of ZrO2-SBSE, the analytical performance of ZrO2-SBSE-CE/indirect UV and ZrO2-SBSE-LVSS-CE/indirect UV was assessed. The limits of detection (LODs, at a signal-to-noise ratio of 3) obtained by ZrO2-SBSE-CE/indirect UV were 13.4–15.9μg/L for PMPA, EMPA and MPA. The relative standard deviations (RSDs, n =7, c =200μg/L) of the corrected peak area for the target analytes were in the range of 6.4–8.8%. Enhancement factors (EFs) in terms of LODs were found to be from 112- to 145-fold. By combining ZrO2 coating SBSE with LVSS as a dual preconcentration strategy, the EFs were magnified up to 1583-fold, and the LODs of ZrO2-SBSE-LVSS-CE/indirect UV were 1.4, 1.2 and 3.1μg/L for PMPA, EMPA, and MPA, respectively. The RSDs (n =7, c =20μg/L) were found to be in the range of 9.0–11.8%. The developed ZrO2-SBSE-LVSS-CE/indirect UV method has been successfully applied to the analysis of PMPA, EMPA, and MPA in different environmental water samples, and the recoveries for the spiked water samples were found to be in the range of 93.8–105.3%.
Source:Journal of Chromatography A, Volume 1247
Pingjing Li, Bin Hu, Xiaoyong Li
In this study, a sensitive, selective and reliable analytical method by combining zirconia (ZrO2) coated stir bar sorptive extraction (SBSE) with large volume sample stacking capillary electrophoresis-indirect ultraviolet (LVSS-CE/indirect UV) was developed for the direct analysis of chemical warfare agent degradation products of alkyl alkylphosphonic acids (AAPAs) (including ethyl methylphosphonic acid (EMPA) and pinacolyl methylphosphonate (PMPA)) and methylphosphonic acid (MPA) in environmental waters. ZrO2 coated stir bar was prepared by adhering nanometer-sized ZrO2 particles onto the surface of stir bar with commercial PDMS sol as adhesion agent. Due to the high affinity of ZrO2 to the electronegative phosphonate group, ZrO2 coated stir bars could selectively extract the strongly polar AAPAs and MPA. After systematically optimizing the extraction conditions of ZrO2-SBSE, the analytical performance of ZrO2-SBSE-CE/indirect UV and ZrO2-SBSE-LVSS-CE/indirect UV was assessed. The limits of detection (LODs, at a signal-to-noise ratio of 3) obtained by ZrO2-SBSE-CE/indirect UV were 13.4–15.9μg/L for PMPA, EMPA and MPA. The relative standard deviations (RSDs, n =7, c =200μg/L) of the corrected peak area for the target analytes were in the range of 6.4–8.8%. Enhancement factors (EFs) in terms of LODs were found to be from 112- to 145-fold. By combining ZrO2 coating SBSE with LVSS as a dual preconcentration strategy, the EFs were magnified up to 1583-fold, and the LODs of ZrO2-SBSE-LVSS-CE/indirect UV were 1.4, 1.2 and 3.1μg/L for PMPA, EMPA, and MPA, respectively. The RSDs (n =7, c =20μg/L) were found to be in the range of 9.0–11.8%. The developed ZrO2-SBSE-LVSS-CE/indirect UV method has been successfully applied to the analysis of PMPA, EMPA, and MPA in different environmental water samples, and the recoveries for the spiked water samples were found to be in the range of 93.8–105.3%.
Highlights
► The ZrO2 coated stir bar is easy to prepare. ► The ZrO2 coated stir bar has excellent pH stability, organic solvent resistance. ► The ZrO2 coated stir bar can selectively extract high polar alkylphosphonic acids. ► ZrO2-SBSE-LVSS-CE/indirect UV was developed for AAPAs and MPA analysis in waters. ► The developed method is sensitive, selective, accurate and low-cost.Retention divergence of terpenes with porous graphitized carbon and C18 stationary phases
25 June 2012,
09:31:04
Publication year:
2012
Source:Journal of Chromatography A, Volume 1247
Paul G. Stevenson, Georges Guiochon
The significant divergence between the retention of 16 terpene standards on porous graphitized carbon (PGC) and C18 packing materials are illustrated. The PGC surface is shown to provide a selectivity toward shape, polarity, and structure that is not afforded by the C18 surface. This observation is illustrated by plots of the retention factors similar to those typically used to represent 2D-HPLC separations. A geometric approach to factor analysis was used to measure the separation divergence together with the selectivity and the product selectivity factors of closely related species. When a methanol mobile phase was used with the PGC surface, a large fraction of the separation space could be utilized. That is further reflected by a spreading angle of 80.3°. The PGC material was also successful at resolving structural isomers where the C18 phase was not. It was also found that the choice of the mobile phase is important when using this material. A much larger degree of space utilization was seen with methanol than with acetonitrile that displayed a spreading angle of only 40.8°.
Source:Journal of Chromatography A, Volume 1247
Paul G. Stevenson, Georges Guiochon
The significant divergence between the retention of 16 terpene standards on porous graphitized carbon (PGC) and C18 packing materials are illustrated. The PGC surface is shown to provide a selectivity toward shape, polarity, and structure that is not afforded by the C18 surface. This observation is illustrated by plots of the retention factors similar to those typically used to represent 2D-HPLC separations. A geometric approach to factor analysis was used to measure the separation divergence together with the selectivity and the product selectivity factors of closely related species. When a methanol mobile phase was used with the PGC surface, a large fraction of the separation space could be utilized. That is further reflected by a spreading angle of 80.3°. The PGC material was also successful at resolving structural isomers where the C18 phase was not. It was also found that the choice of the mobile phase is important when using this material. A much larger degree of space utilization was seen with methanol than with acetonitrile that displayed a spreading angle of only 40.8°.
Highlights
► The retention factors of 16 terpenes on porous graphitized carbon were measured. ► The retention factors of these compounds were also measured on a C18 stationary phase. ► The elution patterns are different enough to allow the use of these columns in 2DLC. ► GAFA and a parameter derived from separation factors characterize phase orthogonality.Highly stable high performance liquid chromatography stationary phase based on direct chemical modification of organic bridges in hybrid silica
25 June 2012,
09:31:04
Publication year:
2012
Source:Journal of Chromatography A, Volume 1247
Hui Yu, Cunyu Jia, Haibo Wu, Guangjun Song, Yu Jin, Yanxiong Ke, Xinmiao Liang
Highly monodisperse 1,4-dimethoxybenzene-bridged organic/inorganic hybrid mesoporous spheres were synthesized by condensation of 1,4-dimethoxy-2,5-bis(triethoxysilyl)benzene using dodecylamine (DDA) and cetyltrimethylammonium bromide (CTAB) as co-templates. The spherical hybrid particles, which have specific surface area of 509m2/g, pore volume of 0.8cm3/g and average pore size of 63Å, were characterized by elemental analysis, SEM, TEM, small angel X-ray scattering, Raman, FT-IR and nitrogen adsorption–desorption analysis. The hybrid material was further chemically modified with C12 chain group via formation of COR bond, which is believed to be far more stable than traditional SiOSi bonding type at low pH condition. At the same time, the hybrid silica substrate has been proved to possess the improved chemical stability at high pH. In this way, combination of the hybrid silica substrate and this advanced modification method enable the stationary phase to be used in extended pH range. The chemical stability of this surface modified 1,4-dimethoxybenzene-bridged hybrid stationary phase was evaluated both at low pH (pH=0.95) and high pH (pH=11.0). Some acidic and alkaline pH chromatographic evaluations were performed to illustrate the advantages of the improved chemical stability of this packing material.
Source:Journal of Chromatography A, Volume 1247
Hui Yu, Cunyu Jia, Haibo Wu, Guangjun Song, Yu Jin, Yanxiong Ke, Xinmiao Liang
Highly monodisperse 1,4-dimethoxybenzene-bridged organic/inorganic hybrid mesoporous spheres were synthesized by condensation of 1,4-dimethoxy-2,5-bis(triethoxysilyl)benzene using dodecylamine (DDA) and cetyltrimethylammonium bromide (CTAB) as co-templates. The spherical hybrid particles, which have specific surface area of 509m2/g, pore volume of 0.8cm3/g and average pore size of 63Å, were characterized by elemental analysis, SEM, TEM, small angel X-ray scattering, Raman, FT-IR and nitrogen adsorption–desorption analysis. The hybrid material was further chemically modified with C12 chain group via formation of COR bond, which is believed to be far more stable than traditional SiOSi bonding type at low pH condition. At the same time, the hybrid silica substrate has been proved to possess the improved chemical stability at high pH. In this way, combination of the hybrid silica substrate and this advanced modification method enable the stationary phase to be used in extended pH range. The chemical stability of this surface modified 1,4-dimethoxybenzene-bridged hybrid stationary phase was evaluated both at low pH (pH=0.95) and high pH (pH=11.0). Some acidic and alkaline pH chromatographic evaluations were performed to illustrate the advantages of the improved chemical stability of this packing material.
Highlights
► Preparation of monodisperse 1,4-dimethoxybenzene-bridged hybrid spheres. ► Directly modification on organic bridges in hybrid silica with C12 group. ► Improvement of chemical stability of HPLC stationary phase. ► Evaluation by analyzing ionic compounds under extended pH mobile phase.Chromatographic models to predict the elution of ionizable analytes by organic modifier gradient in reversed phase liquid chromatography
25 June 2012,
09:31:04
Publication year:
2012
Source:Journal of Chromatography A, Volume 1247
Axel Andrés, Adolfo Téllez, Martí Rosés, Elisabeth Bosch
The retention of an ionizable analyte under RP-HPLC organic modifier gradient elution is strongly affected by its ionization degree which, in turn, depends on its pK a and on the pH of the mobile phase. The values of both parameters change depending on the mobile phase composition and thus retention becomes a parameter quite difficult to predict, particularly when working in gradient mode. In this work, an equation describing the retention of ionizable analytes has been combined with three different models of different complexity, developed for gradient elution of neutral compounds (1, 2, or 3 fitting parameters), in order to predict retention of compounds with acid–base properties with particular buffers. All models have been tested under 16 different gradient patterns (4 linear gradients, 4 concave gradients, 4 convex gradients and 4 combinations between them) for the prediction of the retention time of 12 acid–base compounds (pK a values from 4 to 9) in 3 different buffered mobile phases (pH 5, pH 7 and pH 9) with acetonitrile as organic modifier. The agreement between the experimental and calculated retention times is good for all models. The best results are obtained through the model that depends on three parameters and the accuracy of the two-parameter model is slightly lower but very acceptable too. On the other hand, the predictions performed with the one-parameter model are the less accurate, but good enough to become a valid model taking into account that it requires very little experimental work.
Source:Journal of Chromatography A, Volume 1247
Axel Andrés, Adolfo Téllez, Martí Rosés, Elisabeth Bosch
The retention of an ionizable analyte under RP-HPLC organic modifier gradient elution is strongly affected by its ionization degree which, in turn, depends on its pK a and on the pH of the mobile phase. The values of both parameters change depending on the mobile phase composition and thus retention becomes a parameter quite difficult to predict, particularly when working in gradient mode. In this work, an equation describing the retention of ionizable analytes has been combined with three different models of different complexity, developed for gradient elution of neutral compounds (1, 2, or 3 fitting parameters), in order to predict retention of compounds with acid–base properties with particular buffers. All models have been tested under 16 different gradient patterns (4 linear gradients, 4 concave gradients, 4 convex gradients and 4 combinations between them) for the prediction of the retention time of 12 acid–base compounds (pK a values from 4 to 9) in 3 different buffered mobile phases (pH 5, pH 7 and pH 9) with acetonitrile as organic modifier. The agreement between the experimental and calculated retention times is good for all models. The best results are obtained through the model that depends on three parameters and the accuracy of the two-parameter model is slightly lower but very acceptable too. On the other hand, the predictions performed with the one-parameter model are the less accurate, but good enough to become a valid model taking into account that it requires very little experimental work.
Highlights
► Three different models to predict the retention of ionizable analytes involving three, two and one adjustable parameters, respectively are proposed. ► The proposed models are successfully validated for different buffered mobile phases and gradient patterns. ► The accuracy of the obtained results for the three- and two-parameter models is good and equivalent. ► The accuracy of the obtained results for the one-parameter model is less accurate but good enough taking into account that very little experimental effort is required.Microchannel liquid-flow focusing and cryo-polymerization preparation of supermacroporous cryogel beads for bioseparation
25 June 2012,
09:31:04
Publication year:
2012
Source:Journal of Chromatography A, Volume 1247
Junxian Yun, Changming Tu, Dong-Qiang Lin, Linhong Xu, Yantao Guo, Shaochuan Shen, Songhong Zhang, Kejian Yao, Yi-Xin Guan, Shan-Jing Yao
Polymeric cryogels are sponge-like materials with supermacroporous structure, allowing them to be of interest as new chromatographic supports, cell scaffolds and drug carriers in biological and biomedical areas. The matrices of cryogels are always prepared in the form of monoliths by cryo-polymerization under frozen conditions. However, there are limited investigations on the production of cryogels in the form of adsorbent beads suitable for bioseparation. In this work, we provide a new approach by combining the microchannel liquid-flow focusing with cryo-polymerization for the preparation of polyacrylamide-based supermacroporous cryogel beads with a narrow particle size distribution. The present method was achieved by introducing the aqueous phase solution containing monomer, cross-linker and redox initiators, and the water-immiscible organic oil phase containing surfactant simultaneously into a microchannel with a cross-shaped junction, where the aqueous drops with uniform sizes were generated by the liquid shearing and the segmentation due to the steady flow focusing of the immiscible phase streams. These liquid drops were in situ suspended into the freezing bulk oil phase for cryo-polymerization and the cryogel matrix beads were obtained by thawing after the achievement of polymerization. By grafting the polymer chains containing sulfo binding groups onto these matrix beads, the cation-exchange cryogel beads for protein separation were produced. The results showed that at the aqueous phase velocities from 0.5 to 2.0cm/s and the total velocities of the water-immiscible phase from 2.0 to 6.0cm/s, the obtained cryogel beads by the present method have narrow size distributions with most of the bead diameters in the range from 800 to 1500μm with supermacropores in sizes of about 3–50μm. These beads also have high porosities with the averaged maximum porosity of 96.9% and the mean effective porosity of 86.2%, which are close to those of the polyacrylamide-based cryogel monoliths. The packed bed using the cryogel beads with mean diameter of 1248μm, as an example, has reasonable and acceptable liquid dispersion, but high water permeability (4.29×10−10 m2) and high bed voidage (90.2%) owing to the supermacropores within the beads, enhanced the rapid binding and separation of protein from the feedstock even at high flow velocities. The purity of the obtained lysozyme from chicken egg white by one-step chromatography using the packed bed was in the range of about 78–92% at the flow velocities of 0.5–15cm/min, indicating that the present cryogel beads could be an effective chromatographic adsorbent for primary bioseparation.
Source:Journal of Chromatography A, Volume 1247
Junxian Yun, Changming Tu, Dong-Qiang Lin, Linhong Xu, Yantao Guo, Shaochuan Shen, Songhong Zhang, Kejian Yao, Yi-Xin Guan, Shan-Jing Yao
Polymeric cryogels are sponge-like materials with supermacroporous structure, allowing them to be of interest as new chromatographic supports, cell scaffolds and drug carriers in biological and biomedical areas. The matrices of cryogels are always prepared in the form of monoliths by cryo-polymerization under frozen conditions. However, there are limited investigations on the production of cryogels in the form of adsorbent beads suitable for bioseparation. In this work, we provide a new approach by combining the microchannel liquid-flow focusing with cryo-polymerization for the preparation of polyacrylamide-based supermacroporous cryogel beads with a narrow particle size distribution. The present method was achieved by introducing the aqueous phase solution containing monomer, cross-linker and redox initiators, and the water-immiscible organic oil phase containing surfactant simultaneously into a microchannel with a cross-shaped junction, where the aqueous drops with uniform sizes were generated by the liquid shearing and the segmentation due to the steady flow focusing of the immiscible phase streams. These liquid drops were in situ suspended into the freezing bulk oil phase for cryo-polymerization and the cryogel matrix beads were obtained by thawing after the achievement of polymerization. By grafting the polymer chains containing sulfo binding groups onto these matrix beads, the cation-exchange cryogel beads for protein separation were produced. The results showed that at the aqueous phase velocities from 0.5 to 2.0cm/s and the total velocities of the water-immiscible phase from 2.0 to 6.0cm/s, the obtained cryogel beads by the present method have narrow size distributions with most of the bead diameters in the range from 800 to 1500μm with supermacropores in sizes of about 3–50μm. These beads also have high porosities with the averaged maximum porosity of 96.9% and the mean effective porosity of 86.2%, which are close to those of the polyacrylamide-based cryogel monoliths. The packed bed using the cryogel beads with mean diameter of 1248μm, as an example, has reasonable and acceptable liquid dispersion, but high water permeability (4.29×10−10 m2) and high bed voidage (90.2%) owing to the supermacropores within the beads, enhanced the rapid binding and separation of protein from the feedstock even at high flow velocities. The purity of the obtained lysozyme from chicken egg white by one-step chromatography using the packed bed was in the range of about 78–92% at the flow velocities of 0.5–15cm/min, indicating that the present cryogel beads could be an effective chromatographic adsorbent for primary bioseparation.
Highlights
► We use micro-flow focusing and cryo-polymerization method to prepare cryogel beads. ► The cryogel microbeads were grafted by monomer with cation-exchange groups. ► Protein chromatography by the packed bed of cryogel microbeads was investigated.A study of the thermodynamics of retention of block (co)oligomers using high-performance liquid chromatography/mass spectrometry
25 June 2012,
09:31:04
Publication year:
2012
Source:Journal of Chromatography A, Volume 1247
Lenka Česlová, Pavel Jandera, Petr Česla
Chromatographic behavior of block (co)oligomers of oxyethylene (EO) and oxypropylene (PO) surfactants in reversed-phase HPLC (RP-HPLC) was investigated. The retention of EO/PO block (co)oligomers depends on the distribution of the individual monomer repeat units, but the sequence of the individual blocks also plays a (less significant) role. The enthalpic and entropic contributions of the EO and PO repeat units to the retention were determined from the data measured at changing temperature. In RP-HPLC, the effect of the repeat PO units on separation is higher than the influence of the repeat EO units. In addition to the enthalpic contributions, the retention is significantly influenced by the entropy (possibly by the change of conformation and solvation of adsorbed molecules); dual molar mass distribution according to the number of EO and PO units complicates correct assignment of the chromatographic peaks to the individual (co)oligomers in complex samples based only on the chromatographic retention data. In spite of imperfect chromatographic separation, HPLC coupled with positive ion mode atmospheric pressure chemical ionization mass spectrometry allow identifying unambiguously the dual monomer distribution in the samples of EO–PO block (co)oligomers.
Source:Journal of Chromatography A, Volume 1247
Lenka Česlová, Pavel Jandera, Petr Česla
Chromatographic behavior of block (co)oligomers of oxyethylene (EO) and oxypropylene (PO) surfactants in reversed-phase HPLC (RP-HPLC) was investigated. The retention of EO/PO block (co)oligomers depends on the distribution of the individual monomer repeat units, but the sequence of the individual blocks also plays a (less significant) role. The enthalpic and entropic contributions of the EO and PO repeat units to the retention were determined from the data measured at changing temperature. In RP-HPLC, the effect of the repeat PO units on separation is higher than the influence of the repeat EO units. In addition to the enthalpic contributions, the retention is significantly influenced by the entropy (possibly by the change of conformation and solvation of adsorbed molecules); dual molar mass distribution according to the number of EO and PO units complicates correct assignment of the chromatographic peaks to the individual (co)oligomers in complex samples based only on the chromatographic retention data. In spite of imperfect chromatographic separation, HPLC coupled with positive ion mode atmospheric pressure chemical ionization mass spectrometry allow identifying unambiguously the dual monomer distribution in the samples of EO–PO block (co)oligomers.
Highlights
► Monomer distribution affects the retention behavior of EO–PO (co)oligomers. ► Temperature study reveals enthalpic/entropic contributions to the retention in RP systems. ► Enthalpy–entropy compensation temperature is observed in the oligomer series. ► Mass spectrometry coupled with HPLC allows identification of the individual oligomers.Determination of ortho-phthalaldehyde in water by high performance liquid chromatography and gas chromatography–mass spectrometry after hydrazine derivatization
25 June 2012,
09:31:04
Publication year:
2012
Source:Journal of Chromatography A, Volume 1247
Jin-Aa Oh, Ho-Sang Shin
A simple high performance liquid chromatographic (HPLC) method and a highly sensitive gas chromatography mass spectrometric (GC–MS) method have been established for the determination of ortho-phthalaldehyde (OPA) in water. These methods are based on the derivatization of OPA with hydrazine in water. The following optimum reaction conditions were established: reagent dosage, 20mg/mL of hydrazine; pH 2; reaction for 20min at 70°C. The organic derivative was detected directly by HPLC or after the extraction with methylene chloride/concentration by GC–MS. The limit of detection of OPA in water was 4.0 and 0.3μg/L by HPLC and GC–MS, respectively. The calibration curve showed good linearity with r 2 =0.9993 and r 2 =0.9994 by HPLC and GC–MS, respectively, the accuracy was in a range of 95–105%, and the precision of the assay was less than 13% in water. The HPLC method was simple and reproducible enough to permit the OPA content analysis in the disinfectant products, and the GC–MS method is sensitive enough to permit reliable analysis of OPA to the μg/L level in environmental water.
Source:Journal of Chromatography A, Volume 1247
Jin-Aa Oh, Ho-Sang Shin
A simple high performance liquid chromatographic (HPLC) method and a highly sensitive gas chromatography mass spectrometric (GC–MS) method have been established for the determination of ortho-phthalaldehyde (OPA) in water. These methods are based on the derivatization of OPA with hydrazine in water. The following optimum reaction conditions were established: reagent dosage, 20mg/mL of hydrazine; pH 2; reaction for 20min at 70°C. The organic derivative was detected directly by HPLC or after the extraction with methylene chloride/concentration by GC–MS. The limit of detection of OPA in water was 4.0 and 0.3μg/L by HPLC and GC–MS, respectively. The calibration curve showed good linearity with r 2 =0.9993 and r 2 =0.9994 by HPLC and GC–MS, respectively, the accuracy was in a range of 95–105%, and the precision of the assay was less than 13% in water. The HPLC method was simple and reproducible enough to permit the OPA content analysis in the disinfectant products, and the GC–MS method is sensitive enough to permit reliable analysis of OPA to the μg/L level in environmental water.
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