Determination of nine organophosphorus pesticide residues in corn by capillary electrophoresis with solid phase extraction

A practical method was developed for simultaneously determining phorate, coumaphos, chlorpyrifos, profenofos, dichlorvos, terbufos, dimethoate, parathion and isocarbophos residues in corn samples by solid phase extraction (SPE) and capillary electrophoresis (CE). During the SPE, the effects of ionic strength, pH, extraction temperature and time were studied to evaluate the extraction efficiency of nine organophosphorus. Perform headspace SPE in 10 ml solution, and optimized parameters as follows: NaCl dosage 1.5 g, solution pH 5.5, extraction temperature 50℃ and extraction time 35 min. During the CE process, the effects of separation conditions such as pH value, ionic strength, additional additives, and separation voltage on the separation efficiency of nine organophosphorus were studied. The optimized CE conditions are as follows: the separation solution is a phosphate buffer solution with pH 7.0, containing 45 mmol/L NaCl and 25 mmol/L pyrrolidone, and the separation voltage is 17 kV. All nine organophosphorus showed good linear relationships. Their detection limits were 0.5–0.7 μg/kg. Their quantitation limits were 1.0–1.2 μg/kg. The recoveries were 85.2 % - 113.3 %. The method can be used to determine organophosphorus pesticide residues in corn samples rapidly.