Application of ultrasound-assisted emulsification microextraction followed by gas chromatography for determination of organophosphorus pesticides in water and soil samples

In the present study a fast, simple and efficient method for determination of organophosphorus pesticides (OPPs) in water and soil samples was developed by using ultrasound assisted emulsification microextraction (USAEME) based on applying low density organic solvents. Fourteen microlitres 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 mL of separated toluene (about 4 mu L) was injected into a gas chromatographic instrument equipped with a flame ionization detector for analysis. Under the optimum conditions, preconcentration factors of 2390 and 1390 were obtained for diazinon and chlorpyrifos respectively. The method performance was studied in terms of linear dynamic range (LDRs from 0.01 mu g L-1 to 100 mu g L-1), linearity (r(2) >= 0.9984), precision (repeatability < 8.7%), and extraction percentage (79.9 and 46.3%). Also, limits of detections of 0.01 and 0.1 mu g L-1 were obtained for diazinon and chlorpyrifos respectively. The applicability of the USAEME method was evaluated by the extraction and determination of OPPs from some natural water and soil samples.