GC–MS conditions, the optimization of the retention times and chromatographic resolution were done in the SCAN mode using a 10 µg/ml mixture standard. To quantify the pesticides in the samples, SIM was then chosen and specific ions were selected for each analyte. Fig. 1 shows the chromatogram of a standard extracted directly from the matrix and obtained by GC–MS in the SIM mode. The resolution was considered satisfactory. The some pesticides which presented stereoisomerism, showed peaks corresponding to the cis(Z) and trans(E)isomers.