Development of an improved method to extract pesticide residues in foods using acetontrile with magnesium sulfate and chloroform

Abstract

A multiresidue method was developed based on extraction of 10 g sample with 10 mL acetonitrile and subsequent liquid–liquid partitioning formed by adding 4 g MgSO 4 plus 1 mL chloroform. During the partitioning process, the extraction recoveries of polar analytes were found to be essentially determined by the acetonitrile content in the aqueous phase. The use of MgSO 4 gave the least acetonitrile left in the aqueous phase (lower than 5%) and thus promoting complete partitioning of analytes into the organic phase. At the same time, removal of water from the acetonitrile phase was achieved by adding only a small amount of chloroform with no influence on the acetonitrile content in the aqueous phase, thus leading to decreasing the co-extraction of polar matrix components. The most complete mutual separation of acetonitrile and water was achieved by the joint use of MgSO 4 and chloroform and thus the optimal extraction recovery and analytical selectivity were obtained simultaneously. The new method, with higher recoveries of polar analytes, better analytical selectivity and simpler manipulation, is a claimed improvement to the original QuEChERS method. The proposed method was finally validated by the determination of 20 pesticides in a mixed food matrix by using liquid chromatography tandem mass spectrum (LC–MS/MS). Acceptable linearity, sensitivity, recovery, precision and selectivity results were obtained.