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A simple ultrasound-assisted cloud point extraction (UA-CPE) method combined with high performance liquid chromatography-photodiode array (PDA) detection has been developed for the extraction, preconcentration and determination of benzimidazole anthelmintics (e.g., thiabendazole, oxfendazole, mebendazole, albendazole, and fenbendazole) residues in water and milk samples. Parameters affecting the extraction efficiency, such as concentration of surfactant, content of salt additive, incubation temperature and time, and centrifugation were investigated and optimized. The optimum conditions of UA-CPE were 0.75% (w/v) Triton X-114, 7% (w/v) sodium acetate, 2 min ultrasonication, and 10 min centrifugation. The surfactant-rich phase (SRP) was analyzed by subjecting it to HPLC under gradient condition of 1% (v/v) acetic acid and methanol, an Inertsil ODS column (4.6 Â 150 mm, 5 mm), a flow rate of 1.0 mL min À1 , and photodiode array detection at 296 nm. Under the optimum conditions, linearity was obtained in the range of 0.1-100 mg L À1 with the correlation coefficients (r 2 ) higher than 0.996. A high preconcentration factor of up to 164 was obtained, corresponding to limits of detection (LOD) in the range of 0.005-0.1 mg L À1 . Intra-day (n ¼ 5) and interday (n ¼ 3 Â 3) precisions were obtained with relative standard deviation (RSD) for retention time and peak area lower than 2.0 and 7.0%, respectively. The recoveries for the spiked target anthelmintics at different concentrations in water (3, 10, and 70 mg L À1 ) and milk (20, 50 and 100 mg L À1 ) were in the ranges 81.6-111.4% and 75.3-111.4%, respectively. The proposed UA-CPE method has been demonstrated to be simple, effective, and reliable for the analysis of analytes in the samples studied. In addition, the developed method can be used as an alternative technique to the conventional CPE.

A mixed anionic-cationic surfactant cloud point extraction (CPE) has been developed using sodium dodecyl sulfate (SDS) and tetrabutylammonium bromide (TBABr) for the extraction and preconcentration of organophosphorus pesticides (OPPs) at ambient temperature before analysis by high-performance liquid chromatography. The studied OPPs were azinphos-methyl, parathion-methyl, fenitrothion, diazinon, chlorpyrifos, and prothiophos. The optimum conditions of the mixed anionic-cationic CPE were 50 mmol L(-1) SDS, 100 mmol L(-1) TBABr, and 10% (w/v) NaCl. The extracted OPPs were successfully separated within 11 min using the conditions of a Waters Symmetry C8 column, a flow rate of 0.8 mL min(-1), a gradient elution of methanol and water, and detection at 210 nm. Linearity was found over the range 0.05-5 μg mL(-1), with the correlation coefficients higher than 0.996. The enrichment factor of the target analytes was in the range 6-11, which corresponds to their limits of detection from 1 to 30 ng mL(-1). High precisions (intra-day and inter-day) were obtained with relative standard deviation <1.5% (t(R)) and 10% (peak area). Accuracies (% recovery) of the different spiked OPP concentrations were 82.7-109.1% (water samples) and 80.3-113.3% (fruit juice samples). No contamination by the OPPs was observed in any studied samples.

This review covers recent developments in sample preparations and analytical techniques for determination of residues of carbamate pesticides. Special attention is paid to the newly established microextraction techniques, including cloud-point extraction, dispersive liquid-liquid microextraction, and ultrasound-assisted surfactant-enhanced emulsification microextraction. In addition, extractions using a variety of solvents, as well as miniaturized and on-line sample preparation systems, are discussed. Applications of the different methods for the determination of carbamate pesticide residues in food and environmental matrices are included.