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In this study, flotation-assisted homogeneous liquid-liquid microextraction (FA-HLLME) was developed as a fast, simple, and efficient method for extraction of four polycyclic aromatic hydrocarbons (PAHs) in soil samples followed by gas chromatography-flame ionization detector (GC-FID) analysis. A special home-made extraction cell was designed to facilitate collection of the low-density extraction solvent without a need for centrifugation. In this method, PAHs were extracted from soil samples into methanol and water (1:1, v/v) using ultrasound in two steps followed by filtration as a clean-up step. The filtrate was added into the home-made extraction cell contained mixture of 1.0 mL methanol (homogenous solvent) and 150.0 μL toluene (extraction solvent). Using N(2) flotation, the dispersed extraction solvent was transferred to the surface of the mixture and was collected by means of a micro-syringe. Then, 2 μL of the collected organic solvent was injected into the GC-FID for subsequent analysis. Under optimal conditions, linearity of the method was in the range of 40-1000 μg kg(-1) soil (dry weight). The relative standard deviations in real samples varied from 5.9 to 15.2% (n=4). The proposed method was successfully applied to analyze the target PAHs in soil samples, and satisfactory results were obtained., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Dispersive liquid-liquid microextraction (DLLME) has become a very popular environmentally benign sample-preparation technique, because it is fast, inexpensive, easy to operate with a high enrichment factor and consumes low volume of organic solvent. DLLME is a modified solvent extraction method in which acceptor-to-donor phase ratio is greatly reduced compared with other methods. In this review, in order to encourage further development of DLLME, its combination with different analytical techniques such as gas chromatography (GC), high-performance liquid chromatography (HPLC), inductively coupled plasma-optical emission spectrometry (ICP-OES) and electrothermal atomic absorption spectrometry (ET AAS) will be discussed. Also, its applications in conjunction with different extraction techniques such as solid-phase extraction (SPE), solidification of floating organic drop (SFO) and supercritical fluid extraction (SFE) are summarized. This review focuses on the extra steps in sample preparation for application of DLLME in different matrixes such as food, biological fluids and solid samples. Further, the recent developments in DLLME are presented. DLLME does have some limitations, which will also be discussed in detail. Finally, an outlook on the future of the technique will be given., (Copyright 2009 Elsevier B.V. All rights reserved.)

A simple, rapid and efficient dispersive liquid-liquid microextraction based on the solidification of floating organic drop (DLLME-SFO) method, followed by inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed for the simultaneous preconcentration and determination of heavy metals in water samples. One variable at a time method was applied to select the type of extraction and disperser solvents. Then, an orthogonal array design (OAD) with OA(16) (4(5)) matrix was employed to study the effects of different parameters on the extraction efficiency. Under the best experimental conditions (extraction solvent: 140microL of 1-undecanol; disperser solvent: 2.0mL of acetone; ligand to metal mole ratio: 20; pH: 6 and without salt addition), the enhancement factor ranged from 57 to 96. The calibration graphs were linear in the range of 0.5-250microgL(-1) for Mn, 1.25-250microgL(-1) for Cr, Co and Cu with correlation coefficient (r) better than 0.990. The detection limits were between 0.1 and 0.3microgL(-1). Finally, the developed method was successfully applied to extraction and determination of the mentioned metal ions in the tap, sea and mineral water samples and satisfactory results were obtained., (Copyright 2009 Elsevier B.V. All rights reserved.)

In this study, a fast, simple and efficient ultrasound-assisted emulsification microextraction (USAEME) method was successfully developed based on applying low density organic solvents. Fourteen microliters of toluene was injected slowly into a 12 mL home-designed centrifuge glass vial containing an aqueous sample that was located inside the ultrasonic water bath. The formed emulsion was centrifuged and 2 microL of separated toluene (about 4 microL) was injected into a gas chromatographic system equipped with a flame ionization detector (GC-FID) for analysis. Some polycyclic aromatic hydrocarbons (PAHs) were selected as model compounds for developing the method and evaluating its performance and to compare the efficiency of the proposed method with previously reported techniques. Several factors influencing the emulsification, extraction and collection efficiency such as the nature and volume of organic solvent, emulsification-extraction temperature, ionic strength and equilibrium and centrifugation times were investigated and optimized. Under the optimum conditions, preconcentration factors (PFs) in a range of 1776-2714 were obtained. The performance of the proposed method was studied in terms of linear dynamic range (LDRs from 0.05 to 100 microg L(-1)), linearity (R(2) > or = 0.994), precision (repeatability: RSD% < or = 7.9, reproducibility: RSD% < or = 14.6) and extraction percents (59.2-90.5%). Limits of detection (LODs) in the range of 0.02-0.05 microg L(-1) were obtained for different PAHs. The applicability of the proposed method was evaluated by the extraction and determination of PAHs from several natural water samples.

Dispersive liquid-liquid microextraction (DLLME) coupled with high-performance liquid chromatography (HPLC)-UV detection was applied for the extraction and determination of bisphenol A (BPA) in water samples. An appropriate mixture of acetone (disperser solvent) and chloroform (extraction solvent) was injected rapidly into a water sample containing BPA. After extraction, sedimented phase was analyzed by HPLC-UV. Under the optimum conditions (extractant solvent: 142 microL of chloroform, disperser solvent: 2.0 mL of acetone, and without salt addition), the calibration graph was linear in the range of 0.5-100 microgL(-1) with the detection limit of 0.07 microgL(-1) for BPA. The relative standard deviation (RSD, n=5) for the extraction and determination of 100 microgL(-1) of BPA in the aqueous samples was 6.0%. The results showed that DLLME is a very simple, rapid, sensitive and efficient analytical method for the determination of trace amount of BPA in water samples and suitable results were obtained.

A new microextraction technique termed dispersive liquid-liquid microextraction (DLLME) was developed. DLLME is a very simple and rapid method for extraction and preconcentration of organic compounds from water samples. In this method, the appropriate mixture of extraction solvent (8.0 microL C2Cl4) and disperser solvent (1.00 mL acetone) are injected into the aqueous sample (5.00 mL) by syringe, rapidly. Therefore, cloudy solution is formed. In fact, it is consisted of fine particles of extraction solvent which is dispersed entirely into aqueous phase. After centrifuging, the fine particles of extraction solvent are sedimented in the bottom of the conical test tube (5.0 +/- 0.2 microL). The performance of DLLME is illustrated with the determination of polycyclic aromatic hydrocarbons (PAHs) in water samples by using gas chromatography-flame ionization detection (GC-FID). Some important parameters, such as kind of extraction and disperser solvent and volume of them, and extraction time were investigated. Under the optimum conditions the enrichment factor ranged from 603 to 1113 and the recovery ranged from 60.3 to 111.3%. The linear range was 0.02-200 microg/L (four orders of magnitude) and limit of detection was 0.007-0.030 microg/L for most of analytes. The relative standard deviations (RSDs) for 2 microg/L of PAHs in water by using internal standard were in the range 1.4-10.2% (n = 5). The recoveries of PAHs from surface water at spiking level of 5.0 microg/L were 82.0-111.0%. The ability of DLLME technique in the extraction of other organic compounds such as organochlorine pesticides, organophosphorus pesticides and substituted benzene compounds (benzene, toluene, ethyl benzene, and xylenes) from water samples were studied. The advantages of DLLME method are simplicity of operation, rapidity, low cost, high recovery, and enrichment factor.