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Selected papers from the latest issue:
Solvent-minimized extraction for determining halonitromethanes and trihalomethanes in water
02 July 2012,
13:31:02
Publication year:
2012
Source:Journal of Chromatography A, Volume 1248
I. Montesinos, M. Gallego
Halonitromethanes (HNMs) are a class of nitrogenous disinfection by-products (N-DBPs) that have so far received little attention and focused largely on trichloronitromethane. By contrast, trihalomethanes (THMs) are the most commonly regulated DBPs and have been the subject of much study. This paper reports the first miniaturized system for the simultaneous determination of the nine known HNMs and four THMs in tap and swimming pool water. Micro liquid–liquid extraction (MLLE) is an adaptation of EPA Method 551.1 using ethyl acetate instead of methyl tert-butyl ether as extractant and large injected sample volumes (30μL) in combination with programmed temperature vaporizer–gas chromatography–mass spectrometry for improved sensitivity and selectivity. Because extraction is done with a few microlitres of organic solvent (200μL) and practically all extract is injected into the instrument, MLLE can be regarded as a virtually solvent-free sample preparation technique. The proposed method provided an extraction efficiency of ∼85%, average limits of detection (tribromonitromethane excluded) of 30ng/L and relative standard deviations of ∼6.0%. The influence of various dechlorinating agents on the stability of the thirteen target analytes in treated water was evaluated; the only salt allowing both types of compounds to be efficiently preserved was (NH4)2SO4, but only for 1 day at 4°C. Therefore, acidifying the sample at pH ∼3.4—the optimum value for MLLE—at the time of collection is recommended in order to ensure that both HNMs and THMs retain their integrity for 2 days during storage at 4°C.
Source:Journal of Chromatography A, Volume 1248
I. Montesinos, M. Gallego
Halonitromethanes (HNMs) are a class of nitrogenous disinfection by-products (N-DBPs) that have so far received little attention and focused largely on trichloronitromethane. By contrast, trihalomethanes (THMs) are the most commonly regulated DBPs and have been the subject of much study. This paper reports the first miniaturized system for the simultaneous determination of the nine known HNMs and four THMs in tap and swimming pool water. Micro liquid–liquid extraction (MLLE) is an adaptation of EPA Method 551.1 using ethyl acetate instead of methyl tert-butyl ether as extractant and large injected sample volumes (30μL) in combination with programmed temperature vaporizer–gas chromatography–mass spectrometry for improved sensitivity and selectivity. Because extraction is done with a few microlitres of organic solvent (200μL) and practically all extract is injected into the instrument, MLLE can be regarded as a virtually solvent-free sample preparation technique. The proposed method provided an extraction efficiency of ∼85%, average limits of detection (tribromonitromethane excluded) of 30ng/L and relative standard deviations of ∼6.0%. The influence of various dechlorinating agents on the stability of the thirteen target analytes in treated water was evaluated; the only salt allowing both types of compounds to be efficiently preserved was (NH4)2SO4, but only for 1 day at 4°C. Therefore, acidifying the sample at pH ∼3.4—the optimum value for MLLE—at the time of collection is recommended in order to ensure that both HNMs and THMs retain their integrity for 2 days during storage at 4°C.
Highlights
► A MLLE method has been developed for the whole array determination of HNMs and THMs. ► The water stability is obtained by its acidification at the time of collection. ► LVI using solvent vent mode enhances the sensitivity of the MLLE method.Determination of selected organic contaminants in soil by pressurized liquid extraction and gas chromatography tandem mass spectrometry with in situ derivatization
02 July 2012,
13:31:02
Publication year:
2012
Source:Journal of Chromatography A, Volume 1248
Beatriz Albero, Consuelo Sánchez-Brunete, Esther Miguel, Rosa A. Pérez, José L. Tadeo
The determination of organic contaminants in soil is a real challenge due to the large number of these compounds with quite different physico-chemical properties. In the present work, an analytical method was developed for the simultaneous determination in soil of 40 organic contaminants belonging to different chemical classes: polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polybrominated diphenyl ethers, UV filters, parabens, bisphenols and triclosan. Soil was extracted by pressurized liquid extraction and the extracts, without the need of a clean-up step, were analyzed by gas chromatography–tandem mass spectrometry after in situ derivatization in the gas chromatographic system. In the pressurized liquid extraction step, two extraction cycles were performed with a mixture of ethyl acetate–methanol (90:10, v/v) at 80°C. Recovery of these contaminants from soil samples spiked at levels ranging from 30 to 120ngg−1 was satisfactory for most of the compounds. The developed procedure provided detection method limits from 0.1 to 2.5ngg−1. The analysis of soil samples collected in different agricultural fields confirmed the presence of some of the studied contaminants. Polycyclic aromatic hydrocarbons were the main contaminants detected, parabens and polychlorinated biphenyls were also found but at relatively low concentration levels, 2-ethylhexyl salicylate was the UV filter that appeared most frequently at levels ranging from 17.2 to 43.4ngg−1 and triclosan was found in eight out of fourteen samples, at relatively low concentration levels (0.8–28.6ngg−1).
Source:Journal of Chromatography A, Volume 1248
Beatriz Albero, Consuelo Sánchez-Brunete, Esther Miguel, Rosa A. Pérez, José L. Tadeo
The determination of organic contaminants in soil is a real challenge due to the large number of these compounds with quite different physico-chemical properties. In the present work, an analytical method was developed for the simultaneous determination in soil of 40 organic contaminants belonging to different chemical classes: polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polybrominated diphenyl ethers, UV filters, parabens, bisphenols and triclosan. Soil was extracted by pressurized liquid extraction and the extracts, without the need of a clean-up step, were analyzed by gas chromatography–tandem mass spectrometry after in situ derivatization in the gas chromatographic system. In the pressurized liquid extraction step, two extraction cycles were performed with a mixture of ethyl acetate–methanol (90:10, v/v) at 80°C. Recovery of these contaminants from soil samples spiked at levels ranging from 30 to 120ngg−1 was satisfactory for most of the compounds. The developed procedure provided detection method limits from 0.1 to 2.5ngg−1. The analysis of soil samples collected in different agricultural fields confirmed the presence of some of the studied contaminants. Polycyclic aromatic hydrocarbons were the main contaminants detected, parabens and polychlorinated biphenyls were also found but at relatively low concentration levels, 2-ethylhexyl salicylate was the UV filter that appeared most frequently at levels ranging from 17.2 to 43.4ngg−1 and triclosan was found in eight out of fourteen samples, at relatively low concentration levels (0.8–28.6ngg−1).
Highlights
► Simultaneous analysis of forty organic contaminants in soil. ► In situ derivatization by means of sandwich injection. ► GC–MS/MS analysis after pressurized liquid extraction. ► Determination of organic contaminants in Spanish agricultural fields.Matrine- and oxymatrine-imprinted monodisperse polymers prepared by precipitation polymerization and their applications for the selective extraction of matrine-type alkaloids from Sophora flavescens Aiton
02 July 2012,
13:31:02
Publication year:
2012
Source:Journal of Chromatography A, Volume 1248
Noriko Funaya, Jun Haginaka
Matrine (MT)- and oxymatrine (OMT)-imprinted monodisperse polymers have been prepared by precipitation polymerization. The prepared molecularly imprinted polymers (MIPs) for MT and OMT, MIPMT and MIPOMT, were monodispersed microspheres of 3.3 and 3.9μm in diameter, respectively. Binding experiments and Scatchard analyses revealed that two classes of binding sites were formed on MIPMT and MIPOMT. In addition to shape recognition, ionic and hydrophobic interactions seemed to affect the retention and recognition of MT and OMT on MIPMT and MIPOMT, respectively, in low acetonitrile content, and ionic and hydrophilic interactions affected these properties in high acetonitrile content. MIPMT was used to selectively extract MT and sophocarpine (13,14-dehydromatrine) from Sophora flavescens root, while MIPOMT was used to extract OMT and oxysophocarpine (13,14-dehydrooxymatrine).
Source:Journal of Chromatography A, Volume 1248
Noriko Funaya, Jun Haginaka
Matrine (MT)- and oxymatrine (OMT)-imprinted monodisperse polymers have been prepared by precipitation polymerization. The prepared molecularly imprinted polymers (MIPs) for MT and OMT, MIPMT and MIPOMT, were monodispersed microspheres of 3.3 and 3.9μm in diameter, respectively. Binding experiments and Scatchard analyses revealed that two classes of binding sites were formed on MIPMT and MIPOMT. In addition to shape recognition, ionic and hydrophobic interactions seemed to affect the retention and recognition of MT and OMT on MIPMT and MIPOMT, respectively, in low acetonitrile content, and ionic and hydrophilic interactions affected these properties in high acetonitrile content. MIPMT was used to selectively extract MT and sophocarpine (13,14-dehydromatrine) from Sophora flavescens root, while MIPOMT was used to extract OMT and oxysophocarpine (13,14-dehydrooxymatrine).
Highlights
► Monodispersed MIPs for matrine and oxymatrine by precipitation polymerization. ► Selective recognition of matrine and sophocarpine by a matrine-MIP. ► Selective recognition of oxymatrine and oxysophocarpine by an oxymatrine-MIP. ► Extraction of matrine and sophocarpine in Sophora root by a matrine-MIP. ► Extraction of oxymatrine and oxysophocarpine in Sophora root by an oxymatrine-MIP.Molecularly imprinted-solid phase extraction combined with simultaneous derivatization and dispersive liquid–liquid microextraction for selective extraction and preconcentration of methamphetamine and ecstasy from urine samples followed by gas chromatography
02 July 2012,
13:31:02
Publication year:
2012
Source:Journal of Chromatography A, Volume 1248
Djavanshir Djozan, Mir Ali Farajzadeh, Saeed Mohammad Sorouraddin, Tahmineh Baheri
In this study, a developed technique was reported for extraction and pre-concentration of methamphetamine (MAMP) and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) from urine samples using molecularly imprinted-solid phase extraction (MISPE) along with simultaneous derivatization and dispersive liquid–liquid microextraction (DLLME). Molecularly imprinted microspheres as sorbent in solid phase extraction (SPE) procedure were synthesized using precipitation polymerization with MAMP as the template. Aqueous solution of the target analytes was passed through MAMP-MIP cartridge and the adsorbed analytes were then eluted with methanol. The collected eluate was mixed with butylchloroformate which served as the derivatization reagent as well as the extraction solvent. The mixture was immediately injected into deionized water. After centrifugation, 1μL of the settled organic phase was injected into gas chromatography–flame ionization detection (GC–FID) or gas chromatography–mass spectrometry (GC–MS). Various experimental parameters affecting the performance of both of the steps (MISPE and DLLME) were thoroughly investigated. The calibration graphs were linear in the ranges of 10–1500ngmL−1 (MAMP) and 50–1500ngmL−1 (MDMA), and the detection limits (LODs) were 2 and 18ngmL−1, respectively. The relative standard deviations (%RSDs) obtained for six repeated experiments (100ngmL−1 of each drug) were 5.1% and 6.8% for MAMP and MDMA, respectively. The relative recoveries obtained for the analytes in human urine samples, spiked with different levels of each drug, were within the range of 80–88%.
Source:Journal of Chromatography A, Volume 1248
Djavanshir Djozan, Mir Ali Farajzadeh, Saeed Mohammad Sorouraddin, Tahmineh Baheri
In this study, a developed technique was reported for extraction and pre-concentration of methamphetamine (MAMP) and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) from urine samples using molecularly imprinted-solid phase extraction (MISPE) along with simultaneous derivatization and dispersive liquid–liquid microextraction (DLLME). Molecularly imprinted microspheres as sorbent in solid phase extraction (SPE) procedure were synthesized using precipitation polymerization with MAMP as the template. Aqueous solution of the target analytes was passed through MAMP-MIP cartridge and the adsorbed analytes were then eluted with methanol. The collected eluate was mixed with butylchloroformate which served as the derivatization reagent as well as the extraction solvent. The mixture was immediately injected into deionized water. After centrifugation, 1μL of the settled organic phase was injected into gas chromatography–flame ionization detection (GC–FID) or gas chromatography–mass spectrometry (GC–MS). Various experimental parameters affecting the performance of both of the steps (MISPE and DLLME) were thoroughly investigated. The calibration graphs were linear in the ranges of 10–1500ngmL−1 (MAMP) and 50–1500ngmL−1 (MDMA), and the detection limits (LODs) were 2 and 18ngmL−1, respectively. The relative standard deviations (%RSDs) obtained for six repeated experiments (100ngmL−1 of each drug) were 5.1% and 6.8% for MAMP and MDMA, respectively. The relative recoveries obtained for the analytes in human urine samples, spiked with different levels of each drug, were within the range of 80–88%.
Highlights
► A selective extraction technique using MISPE–DLLME has been developed. ► Molecularly imprinted microspheres were synthesized using precipitation polymerization with MAMP as the template. ► Used derivatization reagent could be acted as extraction solvent in DLLME step. ► DLLME step was performed without addition extraction solvent. ► The proposed method has some advantages in respect of organic solvent consumption, simplicity and extraction efficiency.Hollow fiber-based liquid–liquid–liquid micro-extraction with osmosis: I. Theoretical simulation and verification
02 July 2012,
13:31:02
Publication year:
2012
Source:Journal of Chromatography A, Volume 1248
Qian Wu, Dapeng Wu, Xuhui Geng, Zheng Shen, Yafeng Guan
Osmosis in hollow fiber-based liquid–liquid–liquid micro-extraction (HF-LLLME) was validated and utilized to improve enrichment factor of extraction in this study. When donor phase (sample solution) with higher ion strength than acceptor phase (extraction phase) was used, osmosis was established from acceptor phase, through organic membrane to donor phase. The mass flux expression of analytes across the organic membrane was established based on the convective-diffusive kinetic model, and the kinetic process for HF-LLLME with osmosis was simulated. Simulation results indicated that osmosis from acceptor phase to donor phase can increase enrichment factor of HF-LLLME, accelerate extraction process, and even result in the distribution ratio of analytes between donor and acceptor phase exceeding their partition coefficient. This phenomenon was verified by the experimental data of extraction with six organic acids and four organic bases as the model analytes.
Source:Journal of Chromatography A, Volume 1248
Qian Wu, Dapeng Wu, Xuhui Geng, Zheng Shen, Yafeng Guan
Osmosis in hollow fiber-based liquid–liquid–liquid micro-extraction (HF-LLLME) was validated and utilized to improve enrichment factor of extraction in this study. When donor phase (sample solution) with higher ion strength than acceptor phase (extraction phase) was used, osmosis was established from acceptor phase, through organic membrane to donor phase. The mass flux expression of analytes across the organic membrane was established based on the convective-diffusive kinetic model, and the kinetic process for HF-LLLME with osmosis was simulated. Simulation results indicated that osmosis from acceptor phase to donor phase can increase enrichment factor of HF-LLLME, accelerate extraction process, and even result in the distribution ratio of analytes between donor and acceptor phase exceeding their partition coefficient. This phenomenon was verified by the experimental data of extraction with six organic acids and four organic bases as the model analytes.
Highlights
► Osmosis in HF-LLLME was validated and exploited for the first time. ► Convective-diffusive kinetic model was used to simulate the extraction process. ► The extraction system could break through the equilibrium limit with osmosis. ► The simulation of extraction process was verified by the experimental data.Vortex-assisted liquid–liquid microextraction coupled with derivatization for the fluorometric determination of aliphatic amines
02 July 2012,
13:31:02
Publication year:
2012
Source:Journal of Chromatography A, Volume 1248
Wei-Yao Chang, Chin-Yi Wang, Jeng-Lyan Jan, Yu-Shiu Lo, Chien-Hou Wu
A new one-step derivatization and microextraction technique was developed for the fluorometric determination of C1–C8 linear aliphatic primary amines in complex sample solutions containing high levels of amino acids. In this method, amines were derivatized with o-phthalaldehyde (OPA) and 2-mercaptoethanol (2-ME) in aqueous solution and extracted simultaneously by vortex-assisted liquid–liquid microextraction (VALLME). Parameters affecting the extraction efficiency were investigated in detail. The optimum conditions were as follows: 50μL of isooctane as the extractant phase; 2.0mL aqueous donor samples with 12mM OPA, 24mM 2-ME, and 0.1M borate buffer at pH 10; 1min vortex extraction time; centrifugation for 4min at 6000rpm. After centrifugation, the enriched analytes in the floated extractant phase were determined by HPLC–FL in less than 14min. Under the optimum conditions, the limits of detection were of the order of 0.09–0.31nM. The calibration curves showed good linearity over the investigated concentration range between 0.4 and 40nM. The proposed method has been applied to the determination of aliphatic amines in acidophilus milk, beer, and Cu(II)/amino acid solution.
Source:Journal of Chromatography A, Volume 1248
Wei-Yao Chang, Chin-Yi Wang, Jeng-Lyan Jan, Yu-Shiu Lo, Chien-Hou Wu
A new one-step derivatization and microextraction technique was developed for the fluorometric determination of C1–C8 linear aliphatic primary amines in complex sample solutions containing high levels of amino acids. In this method, amines were derivatized with o-phthalaldehyde (OPA) and 2-mercaptoethanol (2-ME) in aqueous solution and extracted simultaneously by vortex-assisted liquid–liquid microextraction (VALLME). Parameters affecting the extraction efficiency were investigated in detail. The optimum conditions were as follows: 50μL of isooctane as the extractant phase; 2.0mL aqueous donor samples with 12mM OPA, 24mM 2-ME, and 0.1M borate buffer at pH 10; 1min vortex extraction time; centrifugation for 4min at 6000rpm. After centrifugation, the enriched analytes in the floated extractant phase were determined by HPLC–FL in less than 14min. Under the optimum conditions, the limits of detection were of the order of 0.09–0.31nM. The calibration curves showed good linearity over the investigated concentration range between 0.4 and 40nM. The proposed method has been applied to the determination of aliphatic amines in acidophilus milk, beer, and Cu(II)/amino acid solution.
Highlights
► Simultaneous microextraction and OPA/2-ME derivatization for the determination of aliphatic amines. ► Availability of vortex-assisted liquid–liquid microextraction. ► The importance of simultaneous derivatization and extraction procedure for improving sensitivity and selectivity. ► Effective elimination of amino acid interference by isooctane extraction. ► Excellent stabilization of the isoindole derivatives in isooctane.Selective electromembrane extraction at low voltages based on analyte polarity and charge
02 July 2012,
13:31:02
Publication year:
2012
Source:Journal of Chromatography A, Volume 1248
Noelia Cabaleiro Domínguez, Astrid Gjelstad, Andrea Molina Nadal, Henrik Jensen, Nickolaj Jacob Petersen, Steen Honoré Hansen, Knut Einar Rasmussen, Stig Pedersen-Bjergaard
Electromembrane extraction (EME) at low voltage (0–15V) of 29 different basic model drug substances was investigated. The drug substances with log P <2.3 were not extracted at voltages less than 15V. Extraction of drug substances with log P ≥2.3 and with two basic groups were also effectively suppressed by the SLM at voltages less than 15V. Drug substances with log P ≥2.3 and with one basic group were all extracted at low voltages and with a strong compound selectivity which appeared to have some influence from the polar surface area of the compound. For this group of substances, recoveries varied between 0 and 23% at 5V, whereas, recoveries varied between 5.5 and 51% at 15V. Based on mass transfer differences related to charge, polarity, and polar surface, highly selective extractions of drug substances were demonstrated from human plasma, urine, and breast milk. An initial evaluation at low voltage (5V) was compared with similar extractions at a more normal voltage level (50V), and this supported that reliable data can be obtained under these low-voltage (mild) conditions by EME.
Source:Journal of Chromatography A, Volume 1248
Noelia Cabaleiro Domínguez, Astrid Gjelstad, Andrea Molina Nadal, Henrik Jensen, Nickolaj Jacob Petersen, Steen Honoré Hansen, Knut Einar Rasmussen, Stig Pedersen-Bjergaard
Electromembrane extraction (EME) at low voltage (0–15V) of 29 different basic model drug substances was investigated. The drug substances with log P <2.3 were not extracted at voltages less than 15V. Extraction of drug substances with log P ≥2.3 and with two basic groups were also effectively suppressed by the SLM at voltages less than 15V. Drug substances with log P ≥2.3 and with one basic group were all extracted at low voltages and with a strong compound selectivity which appeared to have some influence from the polar surface area of the compound. For this group of substances, recoveries varied between 0 and 23% at 5V, whereas, recoveries varied between 5.5 and 51% at 15V. Based on mass transfer differences related to charge, polarity, and polar surface, highly selective extractions of drug substances were demonstrated from human plasma, urine, and breast milk. An initial evaluation at low voltage (5V) was compared with similar extractions at a more normal voltage level (50V), and this supported that reliable data can be obtained under these low-voltage (mild) conditions by EME.
Highlights
► EME at low voltage of 29 different basic model drug substances was investigated. ► The mass transfer of the drugs was investigated as function of the voltage. ► Extraction selectivity at low voltage appeared to have some influence from the polar surface area. ► Highly selective extractions of drugs were demonstrated based on mass transfer differences related to charge and polarity.Ion-pair in-tube solid-phase microextraction and capillary liquid chromatography using a titania-based column: Application to the specific lauralkonium chloride determination in water
02 July 2012,
13:31:02
Publication year:
2012
Source:Journal of Chromatography A, Volume 1248
M.C. Prieto-Blanco, Y. Moliner-Martínez, P. López-Mahía, P. Campíns-Falcó
A quick, miniaturized and on-line method has been developed for the determination in water of the predominant homologue of benzalkonium chloride, dodecyl dimethyl benzyl ammonium chloride or lauralkonium chloride (C12-BAK). The method is based on the formation of an ion-pair in both in-tube solid-phase microextraction (IT-SPME) and capillary liquid chromatography. The IT-SPME optimization required the study of the length and nature of the stationary phase of capillary and the processed sample volume. Because to the surfactant character of the analyte both, the extracting and replacing solvents, have played a decisive role in the IT-SPME optimized procedure. Conditioning the capillary with the mobile phase which contains the counter ion (acetate), using an organic additive (tetrabutylammonium chloride) added to the sample and a mixture water/methanol as replacing solvent (processed just before the valve is switched to the inject position), allowed to obtain good precision of the retention time and a narrow peak for C12-BAK. A reversed-phase capillary based TiO2 column and a mobile phase containing ammonium acetate at pH 5.0 for controlling the interactions of cationic surfactant with titania surface were proposed. The optimized procedure provided adequate linearity, accuracy and precision at the concentrations interval of 1.5–300μgL−1 .The limit of detection (LOD) was 0.5μgL−1 using diode array detection (DAD). The applicability of proposed IT-SPME-capillary LC method has been assessed in several water samples.
Source:Journal of Chromatography A, Volume 1248
M.C. Prieto-Blanco, Y. Moliner-Martínez, P. López-Mahía, P. Campíns-Falcó
A quick, miniaturized and on-line method has been developed for the determination in water of the predominant homologue of benzalkonium chloride, dodecyl dimethyl benzyl ammonium chloride or lauralkonium chloride (C12-BAK). The method is based on the formation of an ion-pair in both in-tube solid-phase microextraction (IT-SPME) and capillary liquid chromatography. The IT-SPME optimization required the study of the length and nature of the stationary phase of capillary and the processed sample volume. Because to the surfactant character of the analyte both, the extracting and replacing solvents, have played a decisive role in the IT-SPME optimized procedure. Conditioning the capillary with the mobile phase which contains the counter ion (acetate), using an organic additive (tetrabutylammonium chloride) added to the sample and a mixture water/methanol as replacing solvent (processed just before the valve is switched to the inject position), allowed to obtain good precision of the retention time and a narrow peak for C12-BAK. A reversed-phase capillary based TiO2 column and a mobile phase containing ammonium acetate at pH 5.0 for controlling the interactions of cationic surfactant with titania surface were proposed. The optimized procedure provided adequate linearity, accuracy and precision at the concentrations interval of 1.5–300μgL−1 .The limit of detection (LOD) was 0.5μgL−1 using diode array detection (DAD). The applicability of proposed IT-SPME-capillary LC method has been assessed in several water samples.
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