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PubMed2001

Solid-phase microextraction coupled to liquid chromatography for the analysis of phenolic compounds in water.

Solid-phase microextraction (SPME) coupled to high-performance liquid chromatography (HPLC) has been applied to the analysis of priority pollutant phenolic compounds in water samples. Two types of polar fibers [50 microm Carbowax-templated resin (CW-TPR) and 60 microm polydimethylsiloxane-divinylbenzene (PDMS-DVB)] were evaluated. The effects of equilibration time and ionic strength of samples on the adsorption step were studied. The parameters affecting the desorption process, such as desorption mode, solvent composition and desorption time, were optimized. The developed method was used to determine the phenols in spiked river water samples collected in the Douro River, Portugal. Detection limits of 1-10 microg l(-1) were achieved under the optimized conditions.

Chromatography, High Pressure Liquid↗
PubMed2002

Determination of organochlorine pesticides in seawater using liquid-phase hollow fibre membrane microextraction and gas chromatography-mass spectrometry.

The use of hollow fibre membrane microextraction in analytical chemistry has been increasing as the technique is a simple and efficient method for the extraction of trace organic compounds from environmental matrices. A simple liquid-phase microextraction technique using a hollow fibre membrane in conjunction with gas chromatography-mass spectrometry has been developed for the extraction and analysis of organochlorine pesticides (OCPs), i.e. alpha-hexachlorocyclohexane (BHC), lindane, beta-BHC, heptachlor, aldrin, dieldrin, endrin, endosulfan, p,p'-DDD, p,p'-DDT, endrin aldehyde and methoxychlor, from seawater. The technique requires minimal sample preparation time and solvent consumption, and represents a significant advantage over conventional analytical methods. Optimum extraction conditions have been evaluated with respect to sample pH, salt content and stirring rate, as well as solvent type and extraction time. A high level of detection linearity (coefficient of >0.9995, less than 14% RSD) was obtained for OCPs over a range of analyte concentrations between 5 and 100 microg l(-1), with detection limits in the parts per trillion (ppt) to sub-parts per billion range. Comparison between liquid-phase microextraction with hollow fibre membrane and US Environmental Protection Agency Method 508 showed that the novel method has comparable detection limits of between 0.013 and 0.059 microg l(-1) in seawater.

Gas Chromatography-Mass Spectrometry↗
PubMed2006

Coupled two-step microextraction devices with derivatizations to identify hydroxycarbonyls in rain samples by gas chromatography-mass spectrometry.

Coupling a two-step liquid-phase microextraction (LPME) with O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine/bis(trimethylsilyl)trifluoroacetamide (PFBHA)/(BSTFA) derivatization was developed to detect hydroxycarbonyls in rainwater samples using gas chromatography-mass spectrometry (GC-MS). LPME provides a fast and inexpensive pre-concentration, and miniaturized extraction to analyze the target compounds rainwater samples. Derivatization techniques offer a clear method to identify target compounds. The hydroxycarbonyls were determined using two-step derivatizations. Dynamic-LPME was applied in the first derivatization, and head-space single drop derivatization was employed in the second reaction. The LODs varied from 0.023 to 4.75 microg/l. The calibration curves were linear for at least two orders of magnitude with R2>or=0.994. The precision was within 6.5-12%, and the relative recoveries in rainwater were more than 89% (the amount added ranged from 0.3 to 15 microg/l). A field sample was found to contain 2.54 microg/l of hydroxyacetone and 0.110 microg/l of 3-hydroxy-2-butanone. Hydroxyacetone was also detected in one of the tested samples at a concentration of 2.39 microg/l.

Calibration↗
PubMed2000

Solid-phase microextraction coupled with high performance liquid chromatography: a complementary technique to solid-phase microextraction-gas chromatography for the analysis of pesticide residues in strawberries.

Solid-phase microextraction coupled with high performance liquid chromatography has been studied for the analysis of methiocarb, napropamide, fenoxycarb and bupirimate in strawberries. The strawberries were blended and centrifuged. Then, an aliquot of the resulting extracting solution was subjected to solid-phase microextraction (SPME) on a 60 microns polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre for 45 min at room temperature. The extracted pesticides on the SPME fibre were desorbed into SPME/high performance liquid chromatography (HPLC) interface for HPLC analysis with diode-array detection (DAD). The method is organic solvent-free for the whole extraction process and is simple and easy to manipulate. The detection limits were shown to be at low microgram kg-1 level and the linear response covered the range from 0.05 to 2 mg kg-1 of pesticides in strawberries with a regression coefficient larger than 0.99. A good repeatability with RSDs between 2.92 and 9.25% was obtained, depending on compounds.

Chromatography, Gas↗
PubMed2006

Direct determination of chlorophenols in environmental water samples by hollow fiber supported ionic liquid membrane extraction coupled with high-performance liquid chromatography.

The 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) ionic liquid was immobilized in the pores of a polypropylene hollow fiber for hollow fiber-protected liquid-phase microextraction. Analytes including 4-chlorophenol (4-CP), 3-chorophenol (3-CP), 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) were extracted into this ionic liquid membrane, and back extracted into 10microL sodium hydroxide acceptor solution in the lumen of the hollow fiber. Then, the acceptor solution was withdrawn into the high-performance liquid chromatography (HPLC) microsyringe connected to the hollow fiber, and directly injected into the HPLC system for analysis. Some parameters that might affect the extraction efficiency were optimized, and low detection limits (0.5microgL(-1) for 4-CP, 3-CP, DCP and 1.0microgL(-1) for TCP) were obtained. Good repeatability was achieved because of the stability of the hollow fiber-supported ionic liquid membrane. The proposed procedure was applied for direct determination of the four chlorophenols in some real water samples including groundwater, river water, wastewater and tap water. All of the four chlorophenols in these water samples were under the limits of determination, and the recoveries were in the range of 70.0-95.7% at 5microgL(-1) spiked level.

Chlorophenols↗
PubMed2005

Determination of methyl and ethyl esters of methanesulfonic, benzenesulfonic and p-toluenesulfonic acids in active pharmaceutical ingredients by solid-phase microextraction (SPME) coupled to GC/SIM-MS.

The development, optimization and validation of an extraction method for methyl and ethyl esters of various sulfonic acids is presented. The extraction and determination of these esters in active pharmaceutical ingredients (APIs) was accomplished using solid-phase microextraction coupled to GC/MS in the SIM mode. The factors affecting the extraction efficiency are discussed. This method was validated as a limits test and allows the determination of the sulfonic esters at the 5 ppm level in APIs. The method proved to be reproducible (%R.S.D.s less than 6%) and suitable for use with external standard quantitation, and also met basic validation requirements. This method offers numerous advantages over liquid-liquid extraction methods and was also compared to other extraction techniques such as solid-phase extraction (SPE) and liquid-phase microextraction (LPME) also being developed in our laboratories.

Benzenesulfonates↗
PubMed2006

Solid-phase microextraction coupled with liquid chromatography for determination of beta-carotene in food.

Beta-carotene in vegetables and nutritional products is analyzed using solid-phase microextraction (SPME) coupled with liquid chromatography (LC) to improve the speed of analysis and to reduce the consumption of organic solvents. The relative standard deviations (RSDs) of this analytical method for beta-carotene determinations in vegetables and nutritional products are approximately 10% and 5%, respectively. The amount of beta-carotene was found to vary from 0.35 +/- 0.05 ppm to 76.5 +/- 6.9 ppm for several vegetables in Taiwan. This method was linear over the range of 0.4-40 ppm with correlation coefficients higher than 0.997. The experimentally determined level of beta-carotene in nutritional products varied from 3.8 +/- 0.2 ppm to 24.6 +/- 1.1 ppm following SPME-LC. The recoveries of beta-carotene for these measurements following SPME were all higher than 97% +/- 2% (n = 3). The detection limits of beta-carotene for this method were from 0.027 to 0.054 ppm. Conventional solvent extractions take approximately 4-6 h for extraction and reconcentration but SPME takes approximately 1 h. From several tens to hundreds of milliliters, organic solvents can be saved using SPME. SPME provides better analyses on beta-carotene than conventional solvent extraction for nutritional products in terms of speed, precision, simplicity, and solvent consumption.

Beverages↗
PubMed2004

Development and application of polymer-coated hollow fiber membrane microextraction to the determination of organochlorine pesticides in water.

A novel extraction procedure coupled with gas chromatography-mass spectrometric detection for quantification of organochlorine pesticides (OCPs) in water is described. Amphiphilic polyhydroxylated polyparaphenylene (PH-PPP) was synthesized and coated on the surfaces of a porous polypropylene hollow fiber membrane (HFM). Due to the high porosity of the HFM, maximum active surface area to achieve high extraction efficiency is expected. The polymer-coated HFM was used for the extraction of 15 OCPs from water. The extraction efficiency was compared with emerging and established methods such as liquid-phase microextraction (LPME), solid-phase microextraction (SPME) and stir bar sorptive extraction (SBSE) techniques. We term the current procedure as polymer-coated hollow fiber microextraction (PC-HFME). PC-HFME showed good selectivity and sensitivity. Detection limits for OCPs were in the range of 0.001-0.008 microg l(-1). The sensitivity and selectivity of the coated HFM could be adjusted by changing the characteristics of the coated PH-PPP film.

Hydrocarbons, Chlorinated↗
PubMed2006

Analysis of organochlorine pesticides in wine by solvent bar microextraction coupled with gas chromatography with tandem mass spectrometry detection.

A solvent bar microextraction (SBME) technique combined with gas chromatography/tandem mass spectrometry (GC/MS/MS), for the determination of selected organochlorine pesticides (OCPs) in wine samples, is described. In this work the OCPs were extracted and dissolved in a 2-microL aliquot of organic extraction solvent (n-tetradecane) confined within a 1.7-cm length of hollow fiber. Both ends of the hollow fiber (solvent bar) were sealed, and it was placed in an aqueous sample solution for extraction. The effects of solvent selection, sample agitation, extraction time, extraction temperature, and salt concentration on the SBME performance were optimized. The influence of aqueous sample/organic solvent phase ratio was further investigated in detail. High enrichments (1900-7100-fold) could be obtained at an aqueous sample/organic solvent volume ratio of 20 mL/2 microL in this study. Good extraction reproducibility was obtained with relative standard deviation (RSD) values below 12.6%. Comparisons of sensitivity and precision between SBME and dynamic hollow-fiber liquid-phase microextraction were also investigated.

Chemical Fractionation↗
PubMed1999

Automated in-tube solid-phase microextraction coupled with liquid chromatography/electrospray ionization mass spectrometry for the determination of beta-blockers and metabolites in urine and serum samples.

The technique of automated in-tube solid-phase microextraction (SPME) coupled with liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) was evaluated for the determination of beta-blockers in urine and serum samples. In-tube SPME is an extraction technique for organic compounds in aqueous samples, in which analytes are extracted from the sample directly into an open tubular capillary by repeated draw/eject cycles of sample solution. LC/MS analyses of beta-blockers were initially performed by liquid injection onto a LC column. Nine beta-blockers tested in this study gave very simple ESI mass spectra, and strong signals corresponding to [M + H]+ were observed for all beta-blockers. The beta-blockers were separated with a Hypersil BDS C18 column using acetonitrile/methanol/water/acetic acid (15:15:70:1) as a mobile phase. To optimize the extraction of beta-blockers, several in-tube SPME parameters were examined. The optimum extraction conditions were 15 draw/eject cycles of 30 microL of sample in 100 mM Tris-HCl (pH 8.5) at a flow rate of 100 microL/min using an Omegawax 250 capillary (Supelco, Bellefonte, PA). The beta-blockers extracted by the capillary were easily desorbed by mobile-phase flow, and carryover of beta-blockers was not observed. Using in-tube SPME/LC/ESI-MS with selected ion monitoring, the calibration curves of beta-blockers were linear in the range from 2 to 100 ng/mL with correlation coefficients above 0.9982 (n = 18) and detection limits (S/N = 3) of 0.1-1.2 ng/mL. This method was successfully applied to the analysis of biological samples without interference peaks. The recoveries of beta-blockers spiked into human urine and serum samples were above 84 and 71%, respectively. A serum sample from a patient administrated propranolol was analyzed using this method and both propranolol and its metabolites were detected.

Adrenergic beta-Antagonists↗
PubMed2006

Extraction and preconcentration of salbutamol and terbutaline from aqueous samples using hollow fiber supported liquid membrane containing anionic carrier.

This paper presents a new three-phase liquid-phase microextraction (LPME) strategy for extraction and preconcentration of salbutamol (SB) and terbutaline (TB) from aqueous samples, including urine. The drugs were extracted from 11 ml of aqueous sample (source phase; SP) into an organic phase with microliter volume located inside the pores of a polypropylene hollow fiber, and then back-extracted into 24 microl of a second aqueous solution as the receiving phase (RP), located in the lumen of the hollow fiber. In preliminary experiments, we tried to transport the drugs using a pH gradient between the two sides of the hollow fiber. Due to the existence of both amine and phenolic groups on the drugs, very little transport occurred and enrichment factors (EF) less than one were obtained. Further experiments were done in the presence of bis(2-ethylhexyl) monohydrogenphosphoric acid (D2EHPA) or methyltrioctylammonium chloride (Aliquat 336) in the organic phase, to extract drugs from acidic and basic matrices, respectively. Results showed that transport of drugs from alkaline solution into 1M of sodium bromide occurred when the membrane was impregnated with dihexyl ether containing 20% Aliquat 336. To optimize the EF, the effects of different parameters such as the nature of organic solvent used to impregnate the membrane, compositions and volumes of SP and RP, type and concentration of carrier, extraction time and stirring rate were investigated. Optimal results were obtained in the presence of 0.005 M of NaOH (pH 11.70) in the SP, 1M of NaBr in the RP, 20% of Aliquat 336 in dihexyl ether as membrane impregnation solvent, stirring rate of 500 rpm and extraction time of 60 min. Under these conditions, enrichment factors of 52.9 and 213.1, dynamic linear ranges of 20-5000 and 10-5000, and limits of detection of 2.5 and 0.5 ng/ml were obtained for salbutamol and terbutaline, respectively. Also determination of drugs in environmental water and urine samples in the range of nanograms per millilitre with RSDs<10% was possible using HPLC-photodiode array detection or HPLC-MS.

Albuterol↗
PubMed2000

Liquid-liquid extraction procedures for sample enrichment in capillary zone electrophoresis.

This review article presents an overview of applications of liquid-liquid extraction (LLE) for analyte enrichment and clean-up of samples prior to capillary zone electrophoresis (CZE). The basic principles of LLE are discussed with special emphasis on analyte enrichment. In addition, attention is focused on the requirements for the final extract to be compatible with CZE. The paper discusses selected examples from the literature with special emphasis on detection limits in drug analysis and in environmental chemistry. Finally, the paper focus on alternative liquid-phase extraction concepts based on electroextraction, supported liquid membranes, and liquid-phase microextraction.

Body Fluids↗
PubMed2006

Extraction of hydroxyaromatic compounds in river water by liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase.

Liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase technique is described for the extraction of six hydroxyaromatic compounds in river water using a disposable and ready to use hollow fiber. Separation and quantitative analyses were performed using LC with UV detection at 254 nm. Analytes were extracted from the acidified sample solution (donor phase) into the organic solvent impregnated in the pores of the hollow fiber and then back extracted into the alkaline solution (acceptor phase) inside the lumen of the hollow fiber. The fiber was held by a conventional 10 microL LC syringe. The acceptor phase was sandwitched between the plunger and a small volume of the organic solvent (microcap). The acceptor solution was repeatedly moved in and out of the hollow fiber using a syringe pump. This movement provides a fresh acceptor phase to come in contact with the organic phase and thus enhancing extraction kinetics thereby leading to the improvement in enrichment of the analytes. The microcap separates the acceptor phase and the donor phase in addition to being partially responsible for mass transfer of the analytes from the donor solution to the acceptor solution. Under stirring, a fresh donor phase will enter through the open end of the fiber that will also contribute to the mass transfer. Various parameters affecting the extraction efficiency viz type of organic solvent, extraction time, stirring speed, effect of sodium chloride, and concentration of donor and acceptor phases were studied. RSD (3.9-5.6%), correlation coefficient (0.995-0.997), detection limit (2.0-51.2 ng/mL), enrichment factor (339-630), relative recovery (93.2-97.9%), and absolute recovery (33.9-63.0%) have also been investigated. The developed method was applied for the analysis of river water.

Automation↗
PubMedDate not supplied

Simple and rapid determination of amphetamine, methamphetamine, and their methylenedioxy derivatives in urine by automated in-tube solid-phase microextraction coupled with liquid chromatography-electrospray ionization mass spectrometry.

A simple and rapid method for the determination of amphetamine, methamphetamine, and their 3,4-methylenedioxy derivatives in urine samples was developed using automated in-tube solid-phase microextraction (SPME) coupled with liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS). In-tube SPME is an extraction technique for organic compounds in aqueous samples in which analytes are extracted from the sample directly into an open tubular capillary by repeated draw/eject cycles of sample solution. LC-MS analyses of stimulants were initially performed by liquid injection onto an LC column to determine spectra. Five stimulants tested in this study gave very simple ESI mass spectra, and strong signals corresponding to [M+H]+ were observed for all stimulants. The stimulants were well separated with a Supelcosil LC-CN column using acetonitrile/50mM ammonium acetate (15:85) as a mobile phase. In order to optimize the extraction of stimulants, several in-tube SPME parameters were examined. The optimum extraction conditions were 15 draw/eject cycles of 35 microL of sample in 50mM Tris-HCI (pH 8.5) at a flow rate of 100 microL/min using an Omegawax 250 capillary column. The stimulants extracted by the capillary were easily desorbed by mobile phase flow, and carryover of stimulants was not observed. Using in-tube SPME-LC-ESI-MS with selected ion monitoring, the calibration curves of stimulants were linear in the range from 2 to 100 ng/mL with correlation coefficients above 0.9985 (n = 18) and detection limits (S/N = 3) of 0.38-0.82 ng/mL. This method was successfully applied to the analysis of human urine samples without interference peaks. The recoveries of stimulants spiked into urine samples were above 81%.

Amphetamines↗
PubMed2001

Automated on-line in-tube solid-phase microextraction followed by liquid chromatography/electrospray ionization-mass spectrometry for the determination of chlorinated phenoxy acid herbicides in environmental waters.

A method for the determination of six chlorinated phenoxy acid herbicides in river water was developed using in-tube solid-phase microextraction (SPME) followed by liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS). In-tube SPME is an extraction technique for organic compounds in aqueous samples, in which analytes are extracted from a sample directly into an open tubular capillary by repeated draw/eject cycles of the sample solution. Simple mass spectra with strong signals corresponding to [M-H]- and [M-RCOOH]- were observed for all herbicides tested in this study. The best separation of these compounds was obtained with a C18 column using linear gradient elution with a mobile phase of acetonitrile-water containing 5 mmol l-1 dibutylamine acetate (DBA). To optimize the extraction of herbicides, several in-tube SPME parameters were examined. The optimum extraction conditions were 25 draw/eject cycles of 30 microliters of sample in 0.2% formic acid (pH 2) at a flow rate of 200 microliters min-1 using a DB-WAX capillary. The herbicides extracted by the capillary were easily desorbed by 10 microliters acetonitrile. Using in-tube SPME-LC/ESI-MS with time-scheduled selected ion monitoring, the calibration curves of herbicides were linear in the range 0.05-50 ng ml-1 with correlation coefficients above 0.999. This method was successfully applied to the analysis of river water samples without interference peaks. The limit of quantification was in the range 0.02-0.06 ng ml-1 and the limit of detection (S/N = 3) was in the range 0.005-0.03 ng ml-1. The repeatability and reproducibility were in the range 2.5-4.1% and 6.2-9.1%, respectively.

Chromatography, Liquid↗
PubMed2005

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%.

Automation↗
PubMed2006

In-tube solid-phase microextraction-capillary liquid chromatography as a solution for the screening analysis of organophosphorus pesticides in untreated environmental water samples.

This paper describes a method for the selective screening of organophosphorus pesticides in water. In-tube solid-phase microextraction (SPME) in an open capillary column coupled to capillary liquid chromatography (LC) with UV detection has been used to effect preconcentration, separation and detection of the analytes in the same assembly. For in-tube SPME two capillary columns of the same length and different internal diameters and coating thicknesses have been tested and compared, a 30 cm x 0.25 mm I.D., 0.25 micro m thickness coating column, and a 30 cm x 0.1 mm I.D., 0.1 micro m of coating thickness column. In both columns the coating was 95% dimethylpolysiloxane (PDMS)-5% diphenylpolysiloxane. The proposed methodology provided limits of detections (LODs) for the tested organophosphorus pesticides in the 0.1-10 micro g/L range, whereas the direct injection of the samples onto the capillary LC system provided LODs in the 50-1000 micro g/L range. The sensitivity of the proposed in-tube SPME-capillary LC method is adequate to monitorize the analyte levels in drinking water. Several triazines, polycyclic aromatic hydrocarbons (PAHs), nonylphenol, organochloride pesticides or polybrominated diphenyl ethers (PBDEs) have been evaluated as possible interferents. The reliability of the described method is demonstrated by analysing different real water samples.

Chromatography, Liquid↗
PubMed2000

Determination of polycyclic aromatic hydrocarbons in waste water by off-line coupling of solid-phase microextraction with column liquid chromatography.

A new method for the determination of polycyclic aromatic hydrocarbons (PAHs) in waste water using solvent-free solid-phase microextraction (SPME) is described. The PAHs are extracted with a 100 microm polydimethylsiloxane (PDMS) fiber, desorbed in 40 microl acetonitrile and measured with LC and fluorescence detection. The detection limits of this very simple method under the given conditions (extraction from 5 ml sample, extraction time 1 h) are in the range of 1-6 ng l(-1). The standard deviations (n = 6) at a concentration level of 0.8 microg l(-1) are between 1.8 and 14.4%. The procedure was used for the determination of PAHs in contaminated water samples.

Chromatography, Liquid↗