Determination of Multi-Class Pesticide Residues in Lettuce and Cucumber by GC-MSD and the Degradation Study on Vegetables Simultaneously

Abstract

A multi-residue method for determination of pesticide residues in vegetables, using ethyl acetate extraction and determination by means of GC–MSD, is presented. The method includes as many as 27 pesticides such as organophosphorous, organohalogen, organonitrogen and pyrethroids pesticides, which are in common use or forbidden on vegetables in China. After extraction with ethyl acetate, the extract is concentrated and evaporated to dryness and redissolved in ethyl acetate before injection on GC–MSD. The recoveries were obtained in the range 70–100% with 5 exceptions in lettuce and 7 exceptions in cucumber, relative standard deviations between 1.92% and25.39% by means of standard addition to the vegetables blank extracts. The degradation of some pesticides in the 27 was studied by the method developed, the mixture of the pesticides commercial formulations was sparged on the vegetables, then the residues of samples obtained in different time were determined by the developed method. The determination indicated that (all pesticides were used as the instruction): 1.a pesticide, used on different plants, the quantity of the pesticide on the part for people’s dietary differs greatly; 2. some pesticides, degradating slowly and with a large dose, are inappropriate used on vegetables which remain on cropland for a short time. This research does not develop models for pesticides degradation, but provides some data on the safe intervals of the pesticides and a potential method for the study of multi-class pesticides safe intervals on a plant simultaneously.