Advantages of monolithic over particulate columns for multiresidue analysis of organic pollutants by in-tube solid-phase microextraction coupled to capillary liquid chromatography

The performance of a monolithic C(18) column (150 mm×0.2 mm i.d.) for multiresidue organic pollutants analysis by in-tube solid-phase microextraction (IT-SPME)-capillary liquid chromatography has been studied, and the results have been compared with those obtained using a particulate C(18) column (150 mm×0.5 mm i.d., 5 μm). Chromatographic separation has been carried out under isocratic elution conditions, and for detection and identification of the analytes a UV-diode array detector has been employed. Several compounds of different chemical structure and hydrophobicity have been used as model compounds: simazine, atrazine and terbutylazine (triazines), chlorfenvinphos and chlorpyrifos (organophosphorous), diuron and isoproturon (phenylureas), trifluralin (dinitroaniline) and di(2-ethylhexyl)phthalate. The results obtained revealed that the monolithic column was clearly advantageous in the context of multiresidue organic pollutants analysis for a number of reasons: (i) the selectivity was considerably improved, which is of particular interest for the most polar compounds triazines and phenyl ureas that could not be resolved in the particulate column, (ii) the sensitivity was enhanced, and (iii) the time required for the chromatographic separation was substantially shortened. In this study it is also proved that the mobile-phase flow rates used for separation in the capillary monolithic column are compatible with the in-valve IT-SPME methodology using extractive capillaries of dimensions similar to those used in conventional scale liquid chromatography (LC). On the basis of these results a new method is presented for the assessment of pollutants in waters, which permits the characterization of whole samples (4 mL) in less than 30 min, with limits of detection in the range of 5-50 ng/L.     

毛细管内固相微萃取-微柱高效液相色谱在线联用

介绍了一种毛细管内固相微萃取器和微柱高效液相色谱在线联用方法.该萃取器替代定量管直接安装在进样阀上,无需特制接口和专门洗脱液.用10 cm×0.32 mm i.d.×0.6 μm交联OV-1作为萃取柱,对0.4 mL样品萃取富集,用流动相为洗脱液,在15 cm×0.32 mm i.d. 微柱液相色谱分析,该方法使检测灵敏度比直接进样提高10～20倍.对蒽的检出限为0.4 μg/L.     

Fully automated analysis of estrogens in environmental waters by in-tube solid-phase microextraction coupled with liquid chromatography-tandem mass spectrometry

A simple, rapid and sensitive method for the determination of five estrogens, estrone, 17beta-estradiol, estriol, ethynyl estradiol, and diethylstilbestrol, was developed using a fully automated method consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography-tandem mass spectrometry (LC/MS/MS). These estrogens were separated within 8 min by HPLC using an XDB-C8 column and 0.01% ammonia/acetonitrile (60/40, v/v) at a flow rate of 0.2 mL/min. Electrospray ionization conditions in the negative ion mode were optimized for MS/MS detection of the estrogens. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 microL of sample using a Supel-Q PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME LC/MS/MS method, good linearity of the calibration curve (r > or = 0.9996) was obtained in the concentration range from 10 to 200 pg/mL for all compounds examined. The limits of detection (S/N= 3) of the five estrogens examined ranged from 2.7 to 11.7 pg/mL. The in-tube SPME method showed 34-90-fold higher sensitivity than the direct injection method (5 microL injection). This method was applied successfully to the analysis of environmental water samples without any other pretreatment and interference peaks. Several surface water and wastewater samples were collected from the area around Asahi River, and estriol was detected at 35.7 pg/mL in the effluent of a sewage treatment plant. The recoveries of estrogens spiked into river waters were above 86%, except for estriol, and the relative standard deviations were below 0.9-8.8%.     

Determination of fluoroquinolones in environmental waters by in-tube solid-phase microextraction coupled with liquid chromatography-tandem mass spectrometry

We developed a sensitive and useful method for the determination of five fluoroquinolones (FQs), enoxacin, ofloxacin, ciprofloxacin, norfloxacin, and lomefloxacin in environmental waters, using a fully automated method consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography-tandem mass spectrometry (LC/MS/MS). These compounds were analysed within 7 min by high-performance liquid chromatography (HPLC) using a CAPCELL PAK C8 column and aqueous ammonium formate (pH 3.0, 5 mM)/acetonitrile (85/15, v/v) at a flow rate of 0.2 mL/min. Electrospray ionization conditions in the positive ion mode were optimized for MS/MS detection. In order to optimize the extraction of FQs, several in-tube SPME parameters were examined. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL of sample at a flow-rate of 150 μL/min, using a Carboxen 1010 PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase. Using the in-tube SPME LC/MS/MS method, good linearity of the calibration curve (r ≥ 0.997) was obtained in the concentration range from 0.1 to 10 ng/mL for all compounds examined. The limits of detection (S/N = 3) of the five FQs ranged from 7 to 29 pg/mL. The in-tube SPME method showed 60-94-fold higher sensitivity than the direct injection method (5 μL injection). This method was applied successfully to the analysis of environmental water samples without any other pretreatment and interference peaks. Several surface waters and wastewaters were collected from the area around Asahi River, and ofloxacin was detected in wastewater samples of a sewage treatment plant and other two hospitals at 17.5-186.2 pg/mL. The recoveries of FQs spiked into river water were above 81% for a 0.1 or 0.2 ng/mL spiking concentration, and the relative standard deviations were below 1.9-8.6%.     

Selective capillary coating materials for in-tube solid-phase microextraction coupled to liquid chromatography to determine drugs and biomarkers in biological samples: A review

In-tube solid-phase microextraction (in-tube SPME) coupled with high performance liquid chromatography (HPLC) or liquid chromatography coupled to mass spectrometry (LC-MS) successfully determines drugs or biomarkers in biological samples by direct sample injection or by simple sample treatment. This technique uses a capillary column as extraction device. Several capillaries (wall-coated open tubular, sorbent-packed, porous monolithic rods, or fiber-packed) with unique phases have been developed and evaluated, aiming to improve the efficiency and selectivity of the in-tube SPME-LC technique. This review describes new developments and applications occurred in recent years, and discusses future trends with emphasis on new extraction devices and current technology used for the synthesis of selective sorbents for bioanalysis, such as (i) polypyrrole, (ii) restricted-access materials, (iii) immunosorbents, (iv) molecular imprinting polymers, (v) monolithic polymers, and (vi) bi-functional materials.     

Fast speciation analysis of iodophenol compounds in river waters by capillary electrophoresis-inductively coupled plasma-mass spectrometry with off-line solid-phase microextraction

An analytical methodology for the fast separation and determination of iodophenol species in natural water samples was developed using capillary electrophoresis (CE) coupled to inductively coupled plasma-mass spectrometry (ICP-MS). Based on the element-specific and highly sensitive detection provided by ICP-MS, the methodology has been applied to the analysis of 2-iodophenol, 4-iodophenol, and 2,4,6-triiodophenol. The use of solid-phase microextraction (SPME), after proper optimization, improved the signal by a factor of 100 leading to detection limits in the sub microg.L(-1). Different desorption conditions of iodophenol compounds from the SPME microfiber were studied to achieve the optimum preconcentration factor and best analytical performance. Different CE conditions were studied to achieve complete baseline separation of iodophenols in short migration times. Three different CE buffer systems were evaluated using ICP-MS detection. A buffer solution containing 20 mmol.L(-1) 3-(cyclohexylamino)-1-propanesulfonic acid (CAPS) and an applied potential of +22 kV were finally selected leading to a maximum separation time of 6.6 min. A relative standard deviation (%RSD) of about 5.0% for ten consecutive determinations was obtained. Finally, the speciation methodology developed was utilized for the determination of iodophenol compounds in natural water samples.     

On-line analysis of carbonyl compounds with derivatization in aqueous extracts of atmospheric particulate PM10 by in-tube solid-phase microextraction coupled to capillary liquid chromatography

A new device for carbonyl compounds based on coupling on-line and miniaturizing both, sample pretreatment and chromatographic separation, is reported. Two capillary columns, a GC capillary column (95% methyl-5% phenyl substituted backbone, 70 cm × 0.32 mm i.d., 3 μm film thickness) in the injection valve for in-tube solid-phase microextraction (IT-SPME) and a Zorbax SB C18 (150 mm × 0.5 mm i.d., 5 μm particle diameter) LC capillary column were employed. Different combinations of IT-SPME and derivatization using 2,4-dinitrophenylhydrazine (DNPH) were examined for mixtures containing 15 carbonyl compounds (aliphatic, aromatic and unsaturated aldehydes and ketones). A screening analysis of aqueous extracts of atmospheric particulate PM(10) was carried out. Moreover, the possibility of coupling IT-SPME and conventional liquid chromatography is also tested. Derivatization solution and IT-SPME coupled to capillary liquid chromatography provided the best results for achieving the highest sensitivity for carbonyl compounds in atmospheric particulate analysis. Detection limits (LODs) using a photodiode array detector (DAD) were ranged from 30 to 198 ng L(-1), improving markedly those LODs reported by conventional SPME-LC-DAD.     

Experimental design applied to the determination of several contaminants in Duero River by solid-phase microextraction

Several samples taken from Duero River source in Spain have been analysed to evaluate the potential risk of uncontrolled discharges from wood industries located in the surrounding area. Toluene, dodecane, tetradecane, naphthalene, 1-tetradecene, 1-hexadecene, BHT, benzophenone, diisobutylphthalate (DiBP), dibenzofuran and fluoranthene have been selected as representative compounds from solvents and other components of varnishes or coatings, the most likely contamination origin. Solid-phase microextraction (SPME) with further GC-MS has been selected as analytical technique by both its versatility, high process speed, low cost and sensitivity. In order to reach the maximum overall performance, three fibres with different polarity: 100 μm polydimethylsiloxane (PDMS), 85 μm polyacrylate, and 65 μm Carbowax-divinylbenzene have been evaluated. In addition, and due to the high number of involved variables, a two-level full factorial experiment design has been applied for optimisation being sampling time (5-20 min), sorption temperature (room: 50 °C), desorption temperature (minimum recommended +10%, maximum recommended −10%) and salt concentration (NaCl, 0-1 M) as ionic strength modifier the variables under study. After statistical evaluation of experimental design sampling time proved to be the most significant variable, and a more detailed kinetic study has been carried out. The 85 μm polyacrylate fibre was shown to be the most efficient one. Optimum conditions as well as quantitative values are shown and discussed. Toluene, dodecane, tetradecane, benzophenone, BHT and DiBP were found in the concentration range from 2 to 141 ng ml⁻¹.     

In-tube solid-phase microextraction based on hybrid silica monolith coupled to liquid chromatography-mass spectrometry for automated analysis of ten antidepressants in human urine and plasma

A rapid, sensitive and automated in-tube solid-phase microextraction-liquid chromatography-mass spectrometry (in-tube SPME/LC-MS) method was developed for the analysis of ten antidepressants in urine and plasma. A hybrid organic-inorganic silica monolith with cyanoethyl functional groups was prepared and used as a sorbent for in-tube SPME. Integration of the sample extraction, LC separation and MS detection into a single system permitted direct injection of the diluted urine or plasma after filtration. Under the optimized conditions, good extraction efficiencies for the targets were obtained with no matrix interference in the subsequent LC-MS. Automation of the sampling, extraction and separation procedures was realized under the control of a program in this study. The total process time was 30 min and only 30 μL of urine or plasma was required in one analysis cycle. Good linearities were obtained for ten antidepressants with the correlation coefficients (R) above 0.9933. The limits of detection (S/N=3) for ten antidepressants were found to be 0.06-2.84 ng/mL in urine and 0.07-2.95 ng/mL in plasma. The recoveries of antidepressants spiked in urine and plasma were from 75.2% to 113.0%, with relative standard deviations less than 16.5%. The developed method was successfully used to analyze urine sample from ageing patients undergoing therapy with antidepressants.     

固相微萃取-气相色谱/同位素质谱法测定水中挥发性有机物单体碳同位素

建立了采用75μm碳分子筛/聚二甲基硅氧烷(CAR-PDMS)纤维的固相微萃取-气相色谱/同位素质谱联用方法测定水中挥发性有机污染物碳同位素。使用浸入式固相微萃取和顶空固相微萃取方法进行实验确定在低浓度条件下最佳δ13C测试方法。通过使用顶空固相微萃取前处理技术进行单体同位素分析分析灵敏度更高,应用CSIA技术对1,2-二氯乙烯,三氯乙烯,四氯化碳进行单体同位素分析,方法的检出限为70μg/L,与样本的标准偏差小于0.3‰。该法适用于水体中微量挥发性有机污染物的同位素组成测定。     

Speciation analysis of mercury in water samples by dispersive liquid–liquid microextraction coupled to capillary electrophoresis

In this study, a method of pretreatment and speciation analysis of mercury by dispersive liquid–liquid microextraction along with CE was developed. The method was based on the fact that mercury species including methylmercury (MeHg), ethylmercury (EtHg), phenylmercury (PhHg), and Hg(II) were complexed with 1‐(2‐pyridylazo)‐2‐naphthol to form hydrophobic chelates and l ‐cysteine could displace 1‐(2‐pyridylazo)‐2‐naphthol to form hydrophilic chelates with the four mercury species. Factors affecting complex formation and extraction efficiency, such as pH value, type, and volume of extractive solvent and disperser solvent, concentration of the chelating agent, ultrasonic time, and buffer solution were investigated. Under the optimal conditions, the enrichment factors were 102, 118, 547, and 46, and the LODs were 1.79, 1.62, 0.23, and 1.50 μg/L for MeHg, EtHg, PhHg, and Hg(II), respectively. Method precisions (RSD, n = 5) were in the range of 0.29–0.54% for migration time, and 3.08–7.80% for peak area. Satisfactory recoveries ranging from 82.38 to 98.76% were obtained with seawater, lake, and tap water samples spiked at three concentration levels, respectively, with RSD (n = 5) of 1.98–7.18%. This method was demonstrated to be simple, convenient, rapid, cost‐effective, and environmentally benign, and could be used as an ideal alternative to existing methods for analyzing trace residues of mercury species in water samples.     

On-site analysis of volatile nitrosamines in food model systems by solid-phase microextraction coupled to a direct extraction device

Analysis of nitrosamine (NA) standards in a model system was carried out by extraction using SPME coupled to a direct extraction device (DED) and subsequent GC/MS in selected ion monitoring mode. Gelatine (20%, w/v) systems of a NA standard (10 μg L⁻¹) were prepared, in order to mimic food protein matrix systems such as meat and meat products, fish and so on. Different SPME fibre coatings were tested Both divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) and carboxen/polydimethylsiloxane (CAR/PDMS) fibres coupled to DED satisfactorily extracted all nine NA included in the studied standard (EPA 8270 nitrosamines mix, Sigma–Aldrich) from the gelatine system at 25 °C without any sample manipulation. Values of reproducibility, linearity and limit of detection for each type of fibre are reported. SPME-DED appears as a rapid, non-destructive technique for preliminary screening of the presence of toxic substances such as NA in solid foods.     

Poly (methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary for in-tube solid phase microextraction coupled to high performance liquid chromatography and its application to determination of basic drugs in human serum

A poly (methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column was prepared for in-tube solid-phase microextraction. Comparing with the commonly used open tubular extraction capillary, which cannot provide sufficient extraction efficiency since the ratio of its coating volume to that of the capillary void volume is relatively small, the monolithic column with greater phase ratio combined with convective mass transfer provides the possibility to improve the extraction efficiency with shorter capillary. As to poly (methacrylic acid-ethylene glycol dimethacrylate), its hydrophobic main chains and acidic pendant groups make it a superior material for extraction of basic analytes from aqueous matrix.An on-line monolithic capillary column solid phase microextraction (SPME) method was developed for determination of theobromine, theophylline and caffeine in serum samples. The high extraction efficiency was obtained for all the three analytes, yielding the detection limits of 12, 8 and 6.5 ng/mL by UV detection, respectively. Excellent method reproducibility (R.S.D. < 2.9%) was found over a linear dynamic range of 0.05-2 μg/mL in serum sample. The monolithic capillary column was proved to be reusable in coping with serum samples, which would facilitate practical determination of basic drugs.     

Improving analysis of apolar organic compounds by the use of a capillary titania-based column: Application to the direct determination of faecal sterols cholesterol and coprostanol in wastewater samples

This article reports a new procedure for the direct determination of faecal sterols coprostanol and cholesterol in wastewater samples as tracers of human sewage contamination. The method combines in-tube solid-phase microextraction (IT-SPME) for analyte enrichment and capillary liquid chromatography (LC) for separation with diode array detection for identification and quantification. A titania-based polymeric capillary column and a conventional octadecyl silica (ODS) capillary column were evaluated and compared for their ability to separate the analytes. The titania-based column allowed the separation of the analytes in much shorter chromatographic times and with better chromatographic profiles, which in turn resulted in better detectability. In addition, IT-SPME allowed the direct injection into the chromatographic system of sample volumes as large as 200 μL, thus making unnecessary off-line clean-up and concentration steps. In such a way, the tested compounds could be directly analysed in less than 10 min, the limits of detection (LODs) being 10 and 1.2 μg/L for coprostanol and cholesterol, respectively. The reliability of the proposed method was tested by processing several wastewater samples.     

Critical comparison of automated purge and trap and solid-phase microextraction for routine determination of volatile organic compounds in drinking waters by GC-MS

The use of two automated sample preparation techniques, solid-phase microextraction (SPME) and purge and trap (P&T) systems are critically compared for the GC–MS determination of eight volatile organic compounds (VOCs), including trihalomethanes (THMs), in drinking water samples. Compounds chosen for the comparison are regulated by Spanish and European official guidelines for drinking waters. Experimental parameters investigated for the two sample preparation techniques included SPME type of fibers, SPME modality, P&T gas flow, extraction and desorption times and desorption temperatures. Thus, optimal experimental conditions have been worked out for the SPME and P&T techniques. Under such optimised conditions, detection limits, precision and accuracy were evaluated. Both methods fulfilled the values that the official guidelines establish. The P&T–GC–MS method offers LDs ranged from 0.004 to 0.2 ng mL⁻¹, repeatabilities below 6% and recoveries between 81 and 117%; while LDs ranging from 0.008 to 0.7 ng mL⁻¹, 1–12% R.S.D. and recoveries from 80 to 119% were achieved with the SPME–GC–MS method. Finally, we chose P&T–GC–MS method as the best for this determination and we validate this methodology by its application to the analysis of an Aquacheck Interlaboratory Exercise.     

Development and validation of a rapid and wide-scope qualitative screening method for detection and identification of organic pollutants in natural water and wastewater by gas chromatography time-of-flight mass spectrometry

In this work, a multiclass screening method for organic contaminants in natural and wastewater has been developed and validated for qualitative purposes, i.e. to ensure the reliable and sensitive identification of compounds detected in samples at a certain level of concentration. The screening is based on the use of GC-TOF MS, and the sample procedure involves solid phase extraction with C(18) cartridges. Around 150 organic contaminants from different chemical families were investigated, including PAHs, octyl/nonyl phenols, PCBs, PBDEs and a notable number of pesticides, such as insecticides (organochlorines, organophosphorus, carbamates and pyrethroids), herbicides (triazines and chloroacetanilides), fungicides and several relevant metabolites. Surface water, ground water and effluent wastewater were spiked with all target analytes at three concentration levels (0.02, 0.1 and 1 μg/L). Influent wastewater and raw leachate from a municipal solid waste treatment plant were spiked at two levels (0.1 and 1 μg/L). Up to five m/z ions were evaluated for every compound. The identification criterion was the presence of, at least, two m/z ions at the expected retention time, measured at their accurate mass, and the accomplishment of the Q/q(i) intensity ratio within specified tolerances. The vast majority of compounds investigated were correctly identified in the samples spiked at 1 μg/L. When analyte concentration was lowered down to 0.1 μg/L the identification was more problematic, especially in complex-matrix samples like influent wastewater. On the contrary, many contaminants could be properly identified at the lowest level 0.02 μg/L in cleaner matrices. The procedure was applied to the screening of water samples of different origin and matrix composition and allowed the detection of several target contaminants. A highly reliable identification could be carried out thanks to the sensitive full-spectrum acquisition at accurate mass, the high selectivity reached with the use of narrow-mass window extracted ion chromatograms, the low mass errors observed in the positive detections and the Q/q ratio accomplishment.     

Determination of priority organic micro-pollutants in water by gas chromatography coupled to triple quadrupole mass spectrometry

A multiclass method has been developed for screening, quantification and confirmation of organic micro-pollutants in water by gas chromatography coupled to mass spectrometry with a triple quadrupole analyzer. The work has been focused on the determination of more than 50 compounds belonging to different chemical families: 19 organochlorine and organophosphorus insecticides, 6 herbicides, 7 polychlorinated biphenyls, 16 polycyclic aromatics hydrocarbons, 2 brominated diphenyl ethers, and 3 octyl/nonyl phenols and pentachlorobenzene. Most of these analytes are included in the list of priority substances in the framework on European Water Policy.Analyte extraction was performed by solid phase extraction using C₁₈ cartridges, and five isotopically labeled standards were added before extraction as surrogates. Analyses were performed by gas chromatography with tandem mass spectrometry (MS/MS) in electron impact mode. Accuracy and precision were evaluated by means of recovery experiments using water samples fortified at two concentration levels (25 and 250 ng L⁻¹), with satisfactory results for most of analytes. The excellent selectivity and sensitivity reached in selected reaction monitoring mode allowed us satisfactory quantification and confirmation at levels as low as 25 ng L⁻¹. Two MS/MS transitions were acquired for each analyte, using the Q/q intensity ratio as a confirmatory parameter. The method developed was applied to the analysis of surface, ground and wastewater samples collected from the Valencia Region (Spain).Analytical methodology using negative chemical ionization mode was also validated for the organochlorine compounds selected, showing a superior sensitivity and lower detection limits.     

Poly(methacrylic acid-ethylene glycol dimethacrylate) monolith in-tube solid-phase microextraction applied to simultaneous analysis of some amphetamine derivatives in urine by capillary zone electrophoresis

A method based on in-tube solid-phase microextraction and capillary zone electrophoresis (CZE) was proposed for simultaneously determining four amphetamines (amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, and 3,4-methylenedioxymethamphetamine) in urine. A poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column, which can provide sufficient extraction efficiency, was introduced for the extraction of amphetamines from urine samples. The hydrophobic main chains and acidic pendant groups of the monolithic column make it a superior material for extraction of basic analytes from aqueous matrix. After extraction, the samples were analyzed by CZE. The best separation was achieved using a buffer composed of 0.1 M disodium hydrogen phosphate (adjusted to pH 4.5 with 1 M hydrochloric acid) and 20% methanol v/v, with a temperature and voltage of 25 degrees C and 20 kV, respectively. By applying electrokinetic injection with field-amplified sample stacking, detection limits of 25-34 microg/L were achieved. Excellent method of reproducibility was found over a linear range of 0.1-5 mg/L. Determination of these analytes from abusers' urine sample was also demonstrated.     

Determination of chlorobenzenes in environmental samples using solid phase microextraction, thermal desorption and analysis by gas chromatography coupled to FID, ECD, MSD, IRD detectors

Summary A complex method was developed for the determination of chlorobenzenes in soil and groundwater samples. Samples were taken at two sites in Baranya county, where a mixture of chlorobenzene waste was deposited, causing severe contamination in the environment. Clean-up of these sites demands modern and reliable analytical methods. Several sample preparation techniques were used, such as solid phase microextraction (SPME), supercritical fluid extraction (SFE), and a recently developed thermal desorption method. The applicability of various sample preparation methods was compared by measuring recovery percentages, relative standard deviations and by investigating the matrix dependency of these values. Gas chromatography was used for quantitative determination of chlorobenzenes, using MS, IR, FID and ECD detection techniques. Detection levels were as low as 1 ppt in water, and 10 ppt in soil samples. Chlorobenzene concentration was in the range 1 ppt-1 ppm in water and 100 ppb-100 ppm in soil samples. Identification and calibration of these compounds were performed by quantitative standards. This complex analytical method can be used for rapid and precise quantitative and qualitative determination of chlorobenzenes. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997     

Improving sensitivity by large-volume sample stacking using the electroosmotic flow pump to analyze some nonsteroidal anti-inflammatory drugs by capillary electrophoresis in water samples

Large-volume sample stacking using the electroosmotic flow (EOF) pump (LVSEP) has been used to analyze some nonsteroidal anti-inflammatory drugs (NSAIDs) in water samples. With methanol as the run buffer solvent to suppress the EOF, sensitivity was enhanced by 80-100-fold. The sample for the analysis of real water sample was pretreated by solid-phase extraction (SPE). When the method was based on off-line SPE-LVSEP-CE, sensitivity improved by as much as 1000 times.