Simultaneous derivatization and extraction of chlorophenols in water samples with up-and-down shaker-assisted dispersive liquid-liquid microextraction coupled with gas chromatography/mass spectrometric detection.

A new up-and-down shaker-assisted dispersive liquid-liquid microextraction (UDSA-DLLME) for extraction and derivatization of five chlorophenols (4-chlorophenol, 4-chloro-2-methylphenol, 2,4-dichlorophenol, 2,4,6-trichloro-phenol, and pentachlorophenol) has been developed. The method requires minimal solvent usage. The relatively polar, water-soluble, and low-toxicity solvent 1-heptanol (12 µL) was selected as the extraction solvent and acetic anhydride (50 µL) as the derivatization reagent. With the use of an up-and-down shaker, the emulsification of aqueous samples was formed homogeneously and quickly. The derivatization and extraction of chlorophenols were completed simultaneously in 1 min. The common requirement of disperser solvent in DLLME could be avoided. After optimization, the linear range covered over two orders of magnitude, and the coefficient of determination (r (2)) was greater than 0.9981. The detection limit was from 0.05 to 0.2 µg L(-1), and the relative standard deviation was from 4.6 to 10.8 %. Real samples of river water and lake water had relative recoveries from 90.3 to 117.3 %. Other emulsification methods such as vortex-assisted, ultrasound-assisted, and manual shaking-enhanced ultrasound-assisted methods were also compared with the proposed UDSA-DLLME. The results revealed that UDSA-DLLME performed with higher extraction efficiency and precision compared with the other methods.

Up-and-down shaker-assisted ionic liquid-based dispersive liquid-liquid microextraction of benzophenone-type ultraviolet filters.

Sun protection is an important part of our lives. UV filters are widely used to absorb solar radiation in sunscreens. However, excess UV filters constitute persistent groups of organic micropollutants present in the environment. An environmentally friendly ionic-liquid-based up-and-down shaker-assisted dispersive liquid-liquid microextraction device combined with ultra-performance liquid chromatography coupled with photodiode-array detection has been developed to preconcentrate three UV filters (benzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone) from field water samples. In this method, the optimal conditions for the proposed extraction method were: 40 µL [C8MIM][PF6 ] as extraction solvent and 200 µL methanol as disperser solvent were used to extract the UV filters. After up-and-down shaking for 3 min, the aqueous solution was centrifuged at 5000 rpm speed, then using microtube to collect the settled extraction solvent and using ultra-performance liquid chromatography for further analysis. Quantification results indicated that the linear range was 2-1000 ng/mL. The LOD of this method was in the range 0.2-1.3 ng/mL with r(2) ≥ 0.9993. The relative recovery in studies of different types of field water samples was in the range 92-120%, and the RSD was 2.3-7.1%. The proposed method was also applied to the analysis of field samples.

Determination of endocrine-disrupting phenols in water samples by a new manual shaking-enhanced, ultrasound-assisted emulsification microextraction method.

Manual shaking-enhanced, ultrasound-assisted emulsification microextraction (MS-USAEME) combined with ultraperformance liquid chromatography (UPLC) with UV detection has been developed for the determination of five endocrine-disrupting phenols (EDPs) in seawater samples and detergent samples: 4-tert-butylphenol (4-t-BP), 4-cumylphenol (4-CP), 4-tert-octylphenol (4-t-OP), 2,4-di-tert-butylphenol (2,4-di-t-BP) and 4-nonylphenol (4-NP). Optimum conditions were found to be: 25 µL 1-bromohexadecane as extraction solvent, 5 mL of aqueous sample and 1 g of NaCl to control the ionic strength; manual shaking for 10 s; ultrasonication for 1 min; centrifugation for 3 min at 5000 rpm (speed). For MS-USAEME, manual shaking for 10 s is essential for effective extraction when the ultrasonic extraction time is as brief as 1 min. The small volume of aqueous sample enhances the effect of manual shaking significantly. For seawater samples, the limit of detection (LOD) was 0.5-2.8 ng mL(-1), the limit of quantification (LOQ) was 1.8-9.3 ng mL(-1) with the relative standard deviation (RSD) in the range 4.2-10.3%. For detergent samples, the LOD was 0.4-2.4 ng mL(-1), LOQ was 1.6-8.2 ng mL(-1) and RSD 4.7-10.0%. The relative recovery was 96-109% for seawater samples and 81-106% for the detergent samples.

Determination of volatile organic compounds in water using ultrasound-assisted emulsification microextraction followed by gas chromatography.

Volatile organic compounds (VOCs) are toxic compounds in the air, water and land. In the proposed method, ultrasound-assisted emulsification microextraction (USAEME) combined with gas chromatography-mass spectrometry (GC-MS) has been developed for the extraction and determination of eight VOCs in water samples. The influence of each experimental parameter of this method (the type of extraction solvent, volume of extraction solvent, salt addition, sonication time and extraction temperature) was optimized. The procedure for USAEME was as follows: 15 µL of 1-bromooctane was used as the extraction solvent; 10 mL sample solution in a centrifuge tube with a cover was then placed in an ultrasonic water bath for 3 min. After centrifugation, 2 µL of the settled 1-bromooctane extract was injected into the GC-MS for further analysis. The optimized results indicated that the linear range is 0.1-100.0 µg/L and the limits of detection (LODs) are 0.033-0.092 µg/L for the eight analytes. The relative standard deviations (RSD), enrichment factors (EFs) and relative recoveries (RR) of the method when used on lake water samples were 2.8-9.5, 96-284 and 83-110%. The performance of the proposed method was gauged by analyzing samples of tap water, lake water and river water samples.

Application of liquid-liquid-liquid microextraction and high-performance liquid chromatography for the determination of alkylphenols and bisphenol-A in water.

A method termed liquid-liquid-liquid microextraction (LLLME) was utilized to extract 4-t-butylphenol, 4-t-octylphenol, 4-n-nonylphenol, and bisphenol-A from water. The extracted target analytes were separated and quantified by high-performance liquid chromatography using a fluorescence detector. In LLLME, the donor phase (i.e. water sample) was made weakly acidic by adding monobasic potassium phosphate (KH(2) PO(4)); the organic phase adopted was 4-chlorotoluene; the acceptor phase (i.e. enriched extract) was 0.2 M tetraethylammonium hydroxide dissolved in ethylene glycol. This study solves a problem associated with the surface activity of long-chain alkylphenolate ions, permitting LLLME to extract long-chain alkylphenols. Experimental conditions such as acceptor phase composition, organic phase identity, acceptor phase volume, sample agitation, extraction time, and salt addition were optimized. The relative standard deviation (RSD, 2.0-5.8%), coefficient of determination (r(2) 0.9977-0.9999), and detection limit (0.017-0.0048 ng/mL) of the proposed method were achieved under the selected optimized conditions. The method was successfully applied to analyses of lake and tap water samples, and the relative recoveries of target analytes from the spiked lake and tap water samples were 92.8-106.3 and 93.6-105.6%, respectively. The results obtained with the proposed method confirm this microextraction technique to be reliable for the monitoring of alkylphenols and bisphenol-A in water samples.

Improved solvent collection system for a dispersive liquid-liquid microextraction of organochlorine pesticides from water using low-density organic solvent.

In this study, the organochlorine pesticides (OCPs) levels in lake and tap water samples were determined by a dispersive liquid-liquid microextraction method using a low-density organic solvent and an improved solvent collection system (DLLME-ISCS). This method used a very small volume of a solvent of low toxicity (11 µL of 1-nonanol and 400 µL of methanol) to extract OCPs from 10 mL water samples prior to the analysis by GC. After centrifugation in the dispersive liquid-liquid microextraction, there was a liquid organic drop floating between the water surface and the glass wall of the centrifuge tube. The liquid organic drop (with some water phase) was transferred into a microtube (3 mm×15 mm) with a syringe. The organic and aqueous phases were separated in the microtube immediately. Then, 1 µL of the organic solvent (which was in the upper portion of liquid in the microtube) was easily collected by a syringe and injected into the GC-ECD system for the analysis. Under optimum conditions, the linear range of this method was 5-5000 ng/L for most of the analytes. The correlation coefficient was higher than 0.997. Enrichment factors ranged from 1309 to 3629. The relative recoveries ranged from 73 to 119% for lake water samples. The LODs of the method ranged from 0.7 to 9.4 ng/L. The precision of the method ranged from 1.0 to 10.8% for lake water.

Simultaneous derivatization and extraction of amphetamine and methylenedioxyamphetamine in urine with headspace liquid-phase microextraction followed by gas chromatography-mass spectrometry.

A new method is reported for the simultaneous extraction and derivatization of amphetamine (AM) and methylenedioxyamphetamine (MDA) using headspace hollow fiber protected liquid-phase microextraction (HS-HF-LPME); quantitation is by gas chromatograph-mass spectrometry in the selected ion monitoring (SIM) mode. The derivatizing reagent, pentafluorobenzaldehyde (PFBAY), was added to the extraction solvent. The analytes, volatile and basic, were released from the sample matrix into the headspace first, then extracted and derivatized in the solvent. After that, 2 microl of extract was directly injected into the GC-MS system. Parameters affecting extraction efficiency were investigated and optimized. This method showed good linearity in the concentration range investigated (50-350 ng ml(-1) for AM and 50-700 ng ml(-1) for MDA). Excellent repeatability of the extraction (RSD< or = 4%, n=5), and low limits of quantitation (0.25 ng ml(-1) for AM and 1.00 ng ml(-1) for MDA) were achieved. The feasibility of the method was demonstrated by analyzing human urine samples.

Dispersive liquid-liquid microextraction method based on solidification of floating organic drop combined with gas chromatography with electron-capture or mass spectrometry detection.

A simple dispersive liquid-liquid microextraction (DLLME) method based on solidification of a floating organic drop (DLLME-SFO) technique combined with gas chromatography/electron-capture detection (GC/ECD) or gas chromatography/mass spectrometry (GC/MS) has been developed. The proposed method is simple, low in cost, and of high precision. It overcomes the most important problem in DLLME, the high-toxic solvent used. Halogenated organic compounds (HOCs) in water samples were determined as the model compounds. The parameters optimized for the DLLME-SFO technique were as follows: A mixture of 0.5 mL acetone, containing 10 microL 2-dodecanol (2-DD-OH), was rapidly injected by syringe into the 5 mL water sample. After centrifugation, the fine 2-DD-OH droplets (8+/-0.5 microL) were floated at the top of the screwcap test tube. The test tube was then cooled in an ice bath. After 5 min the 2-DD-OH solvent had solidified and was then transferred into a conical vial; it melted quickly at room temperature and 3 microL (for GC/ECD) or 2 microL (for GC/MS) of it was injected into a gas chromatograph for analysis. The limit of detection (LOD) for this technique was 0.005-0.05microgL(-1) for GC/ECD and was 0.005-0.047 microgL(-1) for GC/MS, respectively. The linear range of the calibration curve of DLLME-SFO was from 0.01 to 500 microgL(-1) with a coefficient of estimation (r2)>0.996 for GC/ECD and was from 0.02 to 500 microgL(-1) with a coefficient of estimation (r2)>0.996 for GC/MS.

Application of liquid-liquid-liquid microextraction and ion-pair liquid chromatography coupled with photodiode array detection for the determination of chlorophenols in water.

A method termed as liquid-liquid-liquid microextraction was utilized to extract chlorophenols from water. The extracted chlorophenols, present in anionic form, were then separated, identified, and quantitated by ion-pair high-performance liquid chromatography with photodiode array detection (HPLC/DAD). For trace chlorophenol determination using HPLC/DAD, the chlorophenolate anion provides a better ultraviolet spectrum for quantitative and qualitative analyses than does uncharged chlorophenol. This is due to the auxochromic effect of the phenolate anion. In the study, experimental conditions such as organic phase identity, acceptor phase volume, sample agitation, extraction time, acceptor phase NaOH concentration, donor phase HCl concentration, salt addition, and UV absorption wavelength were optimized. Relative standard deviations (RSD, 2.3-5.4%), coefficients of determination (r2 0.9994-0.9999), and detection limits (0.049-0.081 ng mL(-1)) of the proposed method were investigated under the selected conditions. The method was successfully applied to analyses of reservoir and tap water samples, and the relative recoveries of chlorophenols from the spiked reservoir and tap water samples were 94.1-100.4% and 87.8-101.2%, respectively. The proposed method is capable of identifying and quantitating each analyte to 0.5 ng mL(-1), confirming the HPLC/DAD technique to be quite robust for monitoring trace levels of chlorophenols in water samples.

Determination of triazine herbicides in aqueous samples by dispersive liquid-liquid microextraction with gas chromatography-ion trap mass spectrometry.

A simple and rapid new dispersive liquid-liquid microextraction technique (DLLME) coupled with gas chromatography-ion trap mass spectrometric detection (GC-MS) was developed for the extraction and analysis of triazine herbicides from water samples. In this method, a mixture of 12.0 microL chlorobenzene (extraction solvent) and 1.00 mL acetone (disperser solvent) is rapidly injected by syringe into the 5.00 mL water sample containing 4% (w/v) sodium chloride. In this process, triazines in the water sample are extracted into the fine droplets of chlorobenzene. After centrifuging for 5 min at 6000 rpm, the fine droplets of chlorobenzene are sedimented in the bottom of the conical test tube (8.0+/-0.3 microL). The settled phase (2.0 microL) is collected and injected into the GC-MS for separation and determination of triazines. Some important parameters, viz, type of extraction solvent, identity and volume of disperser solvent, extraction time, and salt effect, which affect on DLLME were studied. Under optimum conditions the enrichment factors and extraction recoveries were high and ranged between 151-722 and 24.2-115.6%, respectively. The linear range was wide (0.2-200 microg L(-1)) and the limits of detection were between 0.021 and 0.12 microg L(-1) for most of the analytes. The relative standard deviations (RSDs) for 5.00 microg L(-1) of triazines in water were in the range of 1.36-8.67%. The performance of the method was checked by analysis of river and tap water samples, and the relative recoveries of triazines from river and tap water at a spiking level of 5.0 microg L(-1) were 85.2-114.5% and 87.8-119.4%, respectively. This method was also compared with solid-phase microextraction (SPME) and hollow fiber protected liquid-phase microextraction (HFP-LPME) methods. DLLME is a very simple and rapid method, requiring less than 3 min. It also has high enrichment factors and recoveries for the extraction of triazines from water.

Determination of organochlorine pesticides in water using solvent cooling assisted dynamic hollow-fiber-supported headspace liquid-phase microextraction.

The organic solvent film formed within a hollow fiber was used as an extraction interface in the headspace liquid-phase microextraction (HS-LPME) of organochlorine pesticides. Some common organic solvents with different vapor pressures (9.33-12,918.9 Pa) were studied as extractants. The results indicated that even the solvent with the highest vapor pressure (cyclohexane) can be used to carry out the extraction successfully. However, those compounds (analytes) with low vapor pressures could not be extracted successfully. In general, the large surface area of the hollow fiber can hasten the extraction speed, but it can increase the risk of solvent loss. Lowering the temperature of the extraction solvent could not only reduce solvent loss (by lowering its vapor pressure) but also extend the feasible extraction time to improve extraction efficiency. In this work, a solvent cooling assisted dynamic hollow-fiber-supported headspace liquid-phase microextraction (SC-DHF-HS-LPME) approach was developed. By lowering the temperature of the solvent, the evaporation can be decreased, the extraction time can be lengthened, and, on the contrary, the equilibrium constant between headspace phase and extraction solvent can be increased. In dynamic LPME, the extracting solvent is held within a hollow fiber, affixed to a syringe needle and placed in the headspace of the sample container. The extracting solvent within the fiber is moved to-and-fro by using a programmable syringe pump. The movement facilitates mass transfer of analyte(s) from the sample to the solvent. Analysis of the extract was carried out by gas chromatography-mass spectrometry (GC-MS). The effects of identity of extraction solvent, extraction temperature, sample agitation, extraction time, and salt concentration on extraction performance were also investigated. Good enrichments were achieved (65-211-fold) with this method. Good repeatabilities of extraction were obtained, with RSD values below 15.2%. Detection limits were 0.209 microg/l or lower.

Determination of Diphenylether Herbicides in Water Samples Using Dispersive Liquid-Liquid Microextraction Combined with High-Performance Liquid Chromatography.

Shaker-assisted dispersive liquid-liquid microextraction (SA-DLLME) and surfactant dispersive liquid-liquid microextraction (SDLLME) have been developed to determine five diphenylether herbicides in water samples using high-performance liquid chromatography with photodiode array detection (HPLC-PDA). For SA-DLLME, an up-and-down shaker-assisted emulsification was used. Extraction was complete in 3 min. Only 30 µL of decyl acetate was required, without a dispersive solvent. The linear range was from 2 to 1000 µg L-1, the coefficient of determination (r2) was better than 0.9992, and the limit of detection (LOD) was from 0.62 to 1.74 µg L-1. The relative recovery (RR) ranged from 90 to 102% for river water, 88 to 104% for lake water, and 93 to 102% for irrigating water. In SDLLME, a microsyringe was used to withdraw and discharge a mixture consisting of an extraction solvent and 1 mg L-1 Tween 60 as a surfactant four times within 10 s to form an emulsified solution. The linear range for the target compounds was from 2 to 1000 µg L-1. The LODs were between 0.72 and 1.38 µg L-1. The RR ranged from 95 to 108% for river water, 96 to 109% for lake water, and 86 to 114% for irrigating water.

Simultaneous derivatization and extraction of primary amines in river water with dynamic hollow fiber liquid-phase microextraction followed by gas chromatography-mass spectrometric detection.

A one-step derivatization and extraction technique for the determination of primary amines in river water by liquid-phase microextraction (LPME) is presented. In this method the primary amines are derivatized with pentafluorobenzaldehyde (PFBAY) in aqueous solution and extracted by dynamic hollow fiber-protected-LPME (HF-LPME) simultaneously. The effects of solvent selection, sample agitation, extraction time, extraction temperature and salt concentration on the extraction performance are investigated. High enrichments (172-244-fold) and good repeatabilities (RSD less than 7.2%) were obtained. Linearity in this developed method was ranging from 1 to 500 ng/ml, and the correlation coefficients (R2) were between 0.992 and 0.998. Comparisons of sensitivity and precision between dynamic HF-LPME and single-drop liquid-phase microextraction (SDME) were also made.

Dynamic hollow fiber protected liquid phase microextraction and quantification using gas chromatography combined with electron capture detection of organochlorine pesticides in green tea leaves and ready-to-drink tea.

The dynamic hollow fiber protected liquid phase microextraction (DHFP-LPME) technique was evaluated for the extraction of organochlorine pesticides (OCPs) in green tea leaves and ready-to-drink tea prior to gas chromatography combined-electron capture detection (GC-ECD) analysis. A conventional microsyringe with a 1.5 cm length of hollow fiber attached to its needle was connected to a syringe pump to perform the extraction. The microsyringe was used as both the microextraction device and the sample introduction device for GC-ECD analysis. In this work, the organochlorine pesticides were extracted and condensed to a volume of 3 microl of organic extracting solvent (1-octanol) confined within a 1.5 cm length of hollow fiber. The effects of extraction solvent, extraction time, sample agitation, plunger speed, and extraction temperature and salt concentration content on the extraction performance were also investigated. Good enrichments were achieved (34-297-fold) with this method, and good repeatabilities of extraction were obtained, with full name (RSDs) below 12.57%. Detection limits were much below 1 microg l(-1) for ready-to-drink tea and much below 1 microg g(-1) for green tea leaves.

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.

Liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase for the extraction of phenoxyacetic acids prior to liquid chromatography detection.

A simple liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase (LLLME/AMADP) technique is described for the quantitative determination of five phenoxyacetic acids in water using a disposable and ready to use hollow fiber. The target compounds were extracted from the acidified sample solution (donor phase) into the organic solvent residing 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 syringe. The acceptor phase was sandwiched 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 assisted by a programmable syringe pump. This repeated movement provides a fresh acceptor phase to come in-contact with the organic phase and thus enhancing extraction kinetics leading to high enrichment of the analytes. The microcap separates the aqueous acceptor phase and the donor phase in addition of being partially responsible for mass transfer of the analytes from donor solution (moving in and out of the hollow fiber from the open end of the fiber) to the acceptor solution. Separation and quantitative analyses were then performed using liquid chromatography (LC) with ultraviolet (UV) detection at 280 nm. Various parameters affecting the extraction efficiency viz. type of organic solvent used for immobilization in the pores of the hollow fiber, extraction time, stirring speed, effect of sodium chloride, and concentration of donor and acceptor phases were studied. Repeatability (RSD, 3.2-7.4%), correlation coefficient (0.996-0.999), detection limit (0.2-2.8 ng ml(-1)) and enrichment factors (129-240) were also investigated. Relative recovery (87-101%) and absolute recoveries (4.6-13%) have also been calculated. The developed method was applied for the analysis of river water.

Quantitative detection of ketamine, norketamine, and dehydronorketamine in urine using chemical derivatization followed by gas chromatography-mass spectrometry.

A repeatable and highly sensitive analytical method using gas chromatography-mass spectrometry (GC-MS) in the selected ion monitoring mode (SIM) is developed for the simultaneous detection of ketamine (KT), norketamine (NK), and newly introduced dehydronorketamine (DHNK) in urine. The test specimen along with the deuterium analogues as internal standards (IS): d4-KT for KT and d4-NK for NK/DHNK, was extracted on an automatic solid-phase extraction (SPE) apparatus. The extracted eluate then was dried and derivatized with N-methyl-bis(trifluoroacetamide) (CF3CONCH3COCF3, MBTFA). Finally, the cooled derivatized solution was directly injected into the GC-MS system for analysis. The proposed process achieves high sensitivity for the detection of KT, NK, and DHNK. Correlation coefficients derived from typical calibration curves in the range of 20-2000 ng/mL are 1.000 for KT and NK, 0.999 for DHNK. The limits of detection (LODs) and limits of quantitation (LOQs) are 0.5-1.0 and 1.5-3.0, respectively. The overall method recoveries of KT, NK, and DHNK are 82.2-93.4. The intra- and inter-day run deviations are smaller than 5.0%. The analytical scheme was also applied to the determination of KT, NK, and DHNK in 20 KT suspected urine specimens, and the results reconfirm that DHNK is a main metabolite of KT.

Up-and-down-shaker-assisted dispersive liquid-liquid microextraction coupled with gas chromatography-mass spectrometry for the determination of fungicides in wine.

An up-and-down-shaker-assisted dispersive liquid-liquid microextraction (UDSA-DLLME) method coupled with gas chromatography-mass spectrometry was developed for the determination of fungicides (cyprodinil, procymidone, fludioxonil, flusilazole, benalaxyl, and tebuconazole) in wine. The developed method requires 11 µL of 1-octanol without the need for dispersive solvents. The total extraction time was approximately 3 min. Under optimum conditions, the linear range of the method was 0.05-100 µg L(-1) for all fungicides and the limit of detection was 0.007-0.025 µg L(-1). The absolute and relative recoveries were 31-83% and 83-107% for white wine, respectively, and 32-85% and 83-108% for red wine, respectively. The intra-day and inter-day precision were 0.5-7.5% and 0.7-6.1%, respectively. Our developed method had good sensitivity and high extraction efficiency. UDSA-DLLME is a desirable method in terms of performance and speed.

Solid-phase microextraction coupled with high-performance liquid chromatography for the determination of phenylurea herbicides in aqueous samples.

Solid-phase microextraction coupled with high-performance liquid chromatography was successfully applied to the analysis of nine phenylurea herbicides (metoxuron, monuron, chlorotoluron, isoproturon, monolinuron, metobromuron, buturon, linuron, and chlorbromuron). Polydimethylsiloxane-divinylbenzene (PDMS-DVB, 60 microm) and Carbowax-templated resin (CW-TPR, 50 microm) fibers were selected from four commercial fibers for further study because of their better extraction efficiencies. The parameters of the desorption procedure were studied and optimized. The effects of the properties of analytes and fiber coatings, carryover, duration and temperature of absorption, pH, organic solvent and ionic strength of samples were also investigated. External calibration with an aqueous standard can be used for the analysis of environmental samples (lake water) using either PDMS-DVB or CW-TPR fibers. Good precisions (1.0-5.9%) are achieved for this method, and the detection limits are at the level of 0.5-5.1 ng/ml.

Analysis of triazine herbicides using an up-and-down-shaker-assisted dispersive liquid-liquid microextraction coupled with gas chromatography-mass spectrometry.

In dispersive liquid-liquid microextraction, a few hundred microliters to a few milliliters of water-miscible dispersive solvent are commonly used to assist emulsification in aqueous samples. In the present study, a consistent and automatic up-and-down-shaker-assisted dispersive liquid-liquid microextraction (UDSA-DLLME) that does not require a dispersive solvent was developed. The enrichment factors (EFs) of the targets obtained using the automatic shaker were 361-1391 for UDSA-DLLME, 51-77 for ultrasonication, and 298-922 for vortexing. The linearity of the method was in the range 0.2-200µgL(-1), and its limit of detections was within 0.02-0.04µgL(-1). The intraday and interday relative standard deviations ranged from 5.7 to 10.0% and 5.5 to 10.3%, respectively. The relative recoveries of river and lake samples spiked with 2.0µgL(-1) of triazines were 94.2-102.2% and 98.5-104.1%, respectively. The technique provided high repeatability and recovery. No matrix interference from river and lake water was observed. The method also achieved high EFs compared with those obtained through other emulsification methods such as vortexing and ultrasonication. UDSA-DLLME is an alternative sample preparation technique with good performance.