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.

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.

Water with low concentration of surfactant in dispersed solvent-assisted emulsion dispersive liquid-liquid microextraction for the determination of fungicides in wine.

A sample preparation method, dispersive liquid-liquid microextraction assisted by an emulsion with low concentration of a surfactant in water and dispersed solvent coupled with gas chromatography-mass spectrometry, was developed for the analysis of the fungicides cyprodinil, procymidone, fludioxonil, flusilazole, benalaxyl, and tebuconazole in wine. A microsyringe was used to withdraw and discharge a mixture of extraction solvent and 240 µL of an aqueous solution of Triton X-100 (the dispersed agent) four times within 10 s to form a cloudy emulsion in the syringe. This emulsion was then injected into a 5 mL wine sample spiked with all of the above fungicides. The total extraction time was approximately 0.5 min. Under optimum conditions using 1-octanol (12 µL) as extraction solvent, the linear range of the method in analysis of all six fungicides was 0.05-100 µg L(-1), and the limit of detection ranged from 0.013 to 0.155 µg L(-1). The absolute recoveries (n = 3) and relative recoveries (n = 3) were 30-83 and 81-108% for white wine at 0.5, 5, and 5 µg L(-1), and 30-92 and 81-110% for red wine, respectively. The intraday (n = 7) and interday (n = 6) relative standard deviations ranged from 4.4 to 8.8% and from 4.3 to 11.2% at 0.5 µg L(-1), respectively. The method achieved high enrichment factors. It is an alternative sample preparation technique with good performance.

Beyond dispersive liquid-liquid microextraction.

Dispersive liquid-liquid microextraction (DLLME) and other dispersion liquid-phase microextraction (LPME) methods have been developed since the first DLLME method was reported in 2006. DLLME is simple, rapid, and affords high enrichment factor, this is due to the large contact surface area of the extraction solvent. DLLME is a method suitable for the extraction in many different water samples, but it requires using chlorinated solvents. In recent years, interest in DLLME or dispersion LPME has been focused on the use of low-toxicity solvents and more conveniently practical procedures. This review examines some of the most interesting developments in the past few years. In the first section, DLLME methods are separated in two categories: DLLME with low-density extraction solvent and DLLME with high-density extraction solvent. Besides these methods, many novel special devices for collecting low-density extraction solvent are also mentioned. In addition, various dispersion techniques with LPME, including manual shaking, air-assisted LPME (aspirating and injecting the extraction mixture by syringe), ultrasound-assisted emulsification, vortex-assisted emulsification, surfactant-assisted emulsification, and microwave-assisted emulsification are described. Besides the above methods, combinations of DLLME with other extraction techniques (solid-phase extraction, stir bar sorptive extraction, molecularly imprinted matrix solid-phase dispersion and supercritical fluid extraction) are introduced. The combination of nanotechnique with DLLME is also introduced. Furthermore, this review illustrates the application of DLLME or dispersion LPME methods to separate and preconcentrate various organic analytes, inorganic analytes, and samples.

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.

Optimization of two different dispersive liquid-liquid microextraction methods followed by gas chromatography-mass spectrometry determination for polycyclic aromatic hydrocarbons (PAHs) analysis in water.

Novel sample preparation methods termed "up-and-down shaker-assisted dispersive liquid-liquid microextraction (UDSA-DLLME)" and "water with low concentration of surfactant in dispersed solvent-assisted emulsion dispersive liquid-liquid microextraction (WLSEME)" coupled with gas chromatography-mass spectrometry (GC-MS) have been developed for the analysis of 11 polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. For UDSA-DLLME, an up-and-down shaker-assisted emulsification was employed. Extraction was complete in 3min. Only 14 µL of 1-heptanol was required, without a dispersive solvent. Under the optimum conditions, the linear range was 0.08-100 µg L(-1), and the LODs were in the range 0.022-0.060 µg L(-1). The enrichment factors (EFs) ranged from 392 to 766. Relative recoveries were between 84% and 113% for river, lake, and field water. In WLSEME, 9 µL of 1-nonanol as extraction solvent and 240 µL of 1 mg L(-1) Triton X-100 as surfactant were mixed in a microsyringe to form a cloudy emulsified solution, which was then injected into the samples. Compared with other surfactant-assisted emulsion methods, WLSEME uses much less surfactant. The linear range was 0.08-100 µg L(-1), and the LODs were 0.022-0.13 µg L(-1). The EFs ranged from 388 to 649. The relative recoveries were 86-114% for all three water specimens.

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.

Water with low concentration of surfactant in dispersed solvent-assisted emulsion dispersive liquid-liquid microextraction for the determination of organochlorine pesticides in aqueous samples.

A novel sample preparation method, "water with low concentration of surfactant in dispersed solvent-assisted emulsion dispersive liquid-liquid microextraction (WLSEME)", coupled with gas chromatography using an electron capture detector (GC-ECD) was developed for the analysis of the organochlorine pesticides (OCPs), heptachlor, α-endosulfan, 4,4-DDE, 2,4-DDD and endrin, in aqueous samples. A microsyringe is used to withdrew and discharge 10-12µL of the extraction solvent and 60-120µL of water as the dispersed solvent (containing 1mgL(-1), Tween 80) 4 times within 10s to form a cloudy emulsified solution in the syringe. This is then injected into an 8mL aqueous sample spiked with all above OCPs. Dodecyl acetate and 2-dodecanol were both selected as extraction solvents to optimize their conditions separately. The total extraction time was about 0.5min. Under optimum conditions, using dodecyl acetate (12µL) as extraction solvent, the linear range of the method was 10-1000ngL(-1) for all OCPs, and the the limits of detection (LODs) ranged from 1 to 5ngL(-1). The absolute recoveries and relative recoveries were from 20.8 to 43.5% and 83.2 to 109.8% for lake water, and 19.9-49.2% and 85.4-115.9% for seawater respectively. In the second method, 2-dodecanol as extraction solvent, the linear range was from 5 to 5000ngL(-1) for the target compounds, and the LODs were between 0.5 and 2ngL(-1). The absolute recoveries and relative recoveries ranged from 25.7 to 42.2% and 96.3-111.2% for sea water, and 22.4-41.9% and 90.7-107.9% for stream water. This could solve several problems, which commonly occur in ultrasound-assisted emulsification micro-extraction (USAEME), dispersive liquid-liquid micro-extraction (DLLME) and other assisted emulsification methods. These problems include analyte degradation, increased solubility of the extraction solvent and analyte, and high toxicity and large volume of the organic solvent used.

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 nitrophenols using ultrahigh pressure liquid chromatography and a new manual shaking-enhanced, ultrasound-assisted emulsification microextraction method based on solidification of a floating organic droplet.

Nitrophenols are toxic compounds in the wastewater. In the proposed method, a new technique using a manual shaking-enhanced, ultrasound-assisted emulsification microextraction (MS-USAEME) method based on solidification of a floating organic droplet combined with ultrahigh pressure liquid chromatography (UHPLC) has been developed for the extraction and determination of nitrophenols in aqueous samples. In this method, the low toxicity extraction solvent 1-undecanol was used to extract the nitrophenols. After centrifugation, ice bath was used to solidify the floating extraction solvent, using microtubes to collect the floated extraction solvent and diluting with 30 µL of dimethyl sulfoxide, then injecting into the UHPLC for further analysis. The relative standard deviations (RSD) were 6-12%, enrichment factors (EFs) were 62-500, the relative recoveries (RR) of this method were 80-110% for spiked lake water samples. The detection limits of this method were 0.5-3.0 µg L⁻¹ for spiked lake water and 0.6-3.2 µg L⁻¹ for spiked agriculture water. The further performance of the proposed method was gauged by analyzing 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.

Development of liquid phase microextraction based on manual shaking and ultrasound-assisted emulsification method for analysis of organochlorine pesticides in aqueous samples.

A novel method using sample preparation method, "ultrasound-assisted emulsification microextraction" (USAEME) with manual shaking, coupled with gas chromatography using and an electron capture detector (GC-ECD) was developed for the analysis of organochlorine pesticides (OCPs) in aqueous samples. The apparatus is simple and easy to operate. After manual shaking for 10s, ultrasound was used to accelerate emulsification of the organic solvent (1-decanol) in aqueous solution. Only 10 µL of the low-toxicity extraction solvent is used in this method; no dispersive solvent is required and the total extraction time is ∼4 min. Manual shaking before ultrasound-assisted emulsification enhances the extraction efficiency by >100%. The effects of horizontal and vertical orientation as well as the location of the sample within the ultrasonic bath were studied. After centrifugation, we used an improved solvent collection system (ISCS) to reduce the amount of extraction solvent required. A 1 µL sample of the extract was injected into the GC column. Under optimum conditions, the linear range of the method is 5-2500 ngL(-1) for most of the OCPs, and the limit of detection of the method ranged from 0.6 to 2.9 ngL(-1).The relative recoveries ranged from 75 to 107% for sea water and from 70 to 99% for field fresh water. The method, which provides good enrichment factors, low LODs and minimization of the consumption of organic solvent, provides a rapid, simple and environment-friendly procedure for determining OCPs in aqueous 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.

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.

Determination of phenoxyacetic acids and chlorophenols in aqueous samples by dynamic liquid-liquid-liquid microextraction with ion-pair liquid chromatography.

Dynamic liquid-liquid-liquid microextraction coupled with ion-pair liquid chromatography (IP-LC) and photodiode array detection was developed and used for the extraction and analysis of chlorinated phenoxyacetic acids (CPAs) and chlorophenols (CPs) from water samples. An organic extraction solvent mixture was chosen to simultaneously and effectively extract both CPAs and CPs from aqueous samples. The method detection limit (MDL) ranged from 0.06 to 0.45 µg L(-1) with good reproducibility. The relative standard deviations were in the range of 2.6-6.5% at lower spiked concentrations and 3.0-4.6% at higher concentrations. Good linearity of analytes was achieved in the range of 0.5-500 µg L(-1). The acceptable relative recoveries (82.9-112.4%) for environmental waters revealed the presence of negligible matrix effects in the case of real samples. The applicability of this newly developed method was illustrated by determinations of CPAs and CPs in environmental water samples.

Low toxic dispersive liquid-liquid microextraction using halosolvents for extraction of polycyclic aromatic hydrocarbons in water samples.

A low toxic dispersive liquid-liquid microextraction (LT-DLLME) combined with gas chromatography-mass spectrometry (GC-MS) had been developed for the extraction and determination of 16 polycyclic aromatic hydrocarbons (PAHs) in water samples. In normal DLLME assay, chlorosolvent had been widely used as extraction solvents; however, these solvents are environmental-unfriendly. In order to solve this problem, we proposed to use low toxic bromosolvent (1-bromo-3-methylbutane, LD(50) 6150mg/kg) as the extraction solvent. In this study we compared the extraction efficiency of five chlorosolvents and thirteen bromo/iodo solvents. The results indicated that some of the bromo/iodo solvents showed better extraction and had much lower toxicity than chlorosolvents. We also found that propionic acid is used as the disperser solvent, as little as 50microL is effective. Under optimum conditions, the range of enrichment factors and extraction recoveries of tap water samples are ranging 372-1308 and 87-105%, respectively. The linear range is wide (0.01-10.00microgL(-1)), and the limits of detection are between 0.0003 and 0.0078microgL(-1) for most of the analytes. The relative standard deviations (RSD) for 0.01microgL(-1) of PAHs in tap water were in the range of 5.1-10.0%. The performance of the method was gauged by analyzing samples of tap water, sea water and lake water samples.

Determination of the steroid hormone levels in water samples by dispersive liquid-liquid microextraction with solidification of a floating organic drop followed by high-performance liquid chromatography.

In this study, the steroid hormone levels in river and tap water samples were determined by using a novel dispersive liquid-liquid microextraction method based on the solidification of a floating organic drop (DLLME-SFO). Several parameters were optimized, including the type and volume of the extraction and dispersive solvents, extraction time, and salt effect. DLLME-SFO is a fast, cheap, and easy-to-use method for detecting trace levels of samples. Most importantly, this method uses less-toxic solvent. The correlation coefficient of the calibration curve was higher than 0.9991. The linear range was from 5 to 1000 microg L(-1). The spiked environmental water samples were analyzed using DLLME-SFO. The relative recoveries ranged from 87% to 116% for river water (which was spiked with 4 microg L(-1) for E1, 3 microg L(-1) for E2, 4 microg L(-1) for EE2 and 9 microg L(-1) for E3) and 89% to 102% for tap water (which was spiked with 6 microg L(-1) for E1, 5 microg L(-1) for E2, 6 microg L(-1) for EE2 and 10 microg L(-1) for E3). The detection limits of the method ranged from 0.8 to 2.7 microg L(-1) for spiked river water and 1.4 to 3.1 microg L(-1) for spiked tap water. The methods precision ranged from 8% to 14% for spiked river water and 7% to 14% for spiked tap water.

Dispersive liquid-liquid-liquid microextraction combined with liquid chromatography for the determination of chlorophenoxy acid herbicides in aqueous samples.

A novel sample preparation method "Dispersive liquid-liquid-liquid microextraction" (DLLLME) was developed in this study. DLLLME was combined with liquid chromatography system to determine chlorophenoxy acid herbicide in aqueous samples. DLLLME is a rapid and environmentally friendly sample pretreatment method. In this study, 25microL of 1,1,2,2-tetrachloroethane was added to the sample solution and the targeted analytes were extracted from the donor phase by manually shaking for 90s. The organic phase was separated from the donor phase by centrifugation and was transferred into an insert. Acceptor phase was added to this insert. The analytes were then back-extracted into the acceptor phase by mixing the organic and acceptor phases by pumping those two solutions with a syringe plunger. After centrifugation, the organic phase was settled and removed with a microsyringe. The acceptor phase was injected into the UPLC system by auto sampler. Fine droplets were formed by shaking and pumping with the syringe plunger in DLLLME. The large interfacial area provided good extraction efficiency and shortened the extraction time needed. Conventional LLLME requires an extraction time of 40-60min; an extraction time of approximately 2min is sufficient with DLLLME. The DLLLME technique shows good linearity (r(2)>or=0.999), good repeatability (RSD: 4.0-12.2% for tap water; 5.7-8.5% for river water) and high sensitivity (LODs: 0.10-0.60microg/L for tap water; 0.11-0.95microg/L for river water).

Dispersive liquid-liquid microextraction method based on solidification of floating organic drop for extraction of organochlorine pesticides in water samples.

A new simple and rapid dispersive liquid-liquid microextraction method has been developed for the extraction and analysis of organochlorine pesticides (OCPs) in water samples. The method is based on the solidification of a floating organic drop (DLLME-SFO) and is combined with gas chromatography/electron capture detection (GC/ECD). Very little solvent is required in this method. The disperser solvent (200microL acetonitrile) containing 10microL hexadecane (HEX) is rapidly injected by a syringe into the 5.0mL water sample. After centrifugation, the fine HEX droplets (6+/-0.5microL) float at the top of the screw-cap test tube. The test tube is then cooled in an ice bath. After 5min, the HEX solvent solidifies and is then transferred into a conical vial, where it melts quickly at room temperature, and 1microL of it is injected into a gas chromatograph for analysis. Under optimum conditions, the enrichment factors and extraction recoveries are high and range between 37-872 and 82.9-102.5%, respectively. The linear range is wide (0.025-20microgL(-1)), and the limits of detection are between 0.011 and 0.11microgL(-1) for most of the analytes. The relative standard deviation (RSD) for 1microgL(-1) of OCPs in water was in the range of 5.8-8.8%. The performance of the method was gauged by analyzing samples of lake and tap water.