A cloud-point extraction (CPE) method using Triton X-114 non-ionic surfactant was developed for the extraction and preconcentration of carbamate insecticide residues (i.e., methomyl, propoxur, carbofuran, carbaryl, isoprocarb, and promecarb) in fruit samples. The optimum conditions of CPE were 1.5% (w/v) Triton X-114, 7.0% (w/v) NaCl and 20 min equilibrated at 45 degrees C. The surfactant-rich phase was then analyzed by reversed-phase high-performance liquid chromatography with ultraviolet detection at 270 nm, under gradient separation using methanol and 0.1% (v/v) acetic acid. Under the study conditions, six carbamate insecticides were successfully separated within 27 min. Good reproducibility was obtained with the relative standard deviation of <3% for retention time and <9% for peak area. Limits of detection in the studied fruit samples were in the range of 0.1-1.0 mg kg(-1). No carbamate insecticides were detected in the studied fruit samples. The high recoveries of the spiked fruit samples were obtained in the range 80.0-107%. The CPE method has been shown to be a potential useful methodology for the preconcentration of the target analytes, with a preconcentration factor of 14. Moreover, the method is simple, has high sensitivity, consumes much less solvent than traditional methods, and is environmental friendly.

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Reversed electrode polarity stacking mode (REPSM) coupled to micellar electrokinetic chromatography (MEKC) was employed for the simultaneous determination of carbamate insecticide residues in fruit juice samples. A mixture of the studied insecticides (i.e., methomyl, propoxur, carbofuran, carbaryl, isoprocarb, and promecarb) in 10 mmol L −1 phosphate buffer (pH 7.0) was introduced into the capillary tube by hydrodynamic injection at 0.5 psi for 30 s followed by removal of the sample matrix at −15 kV for 0.5 min. The analytes were successfully separated within 8 min using 10 mmol L −1 borate buffer containing 60 mmol L −1 sodium dodecyl sulfate at pH 9.5, and photodiode array detection at 205, 214, and 225 nm. The REPSM-MEKC gave stacking enhancement factors of about 4-13, compared to that without stacking. The limits of detection were in the range 0.01-0.10 mg L −1 , which is acceptable with respect to the maximum residue limits. Good precisions were obtained with relative standard deviation lower than 1.8% (for migration time) and 10% (for peak area). The recoveries for most fruit juice samples were acceptable (>80%). No contamination of the studied carbamates was observed in any sample. The proposed method is simple and effective for preconcentration and removal of matrix interferences in a single step for the determination of the studied carbamate insecticides.

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