Improvement of the QuEChERS method coupled with GC–MS/MS for the determination of pesticide residues in fresh fruit and vegetables

An enhanced methodology for the determination of 31 currently used pesticides (13 insecticides including 7 acaricides, 17 fungicides and 1 herbicide) in food samples was proposed to meet the increasingly stringent legal requirements concerning the maximum pesticide residue limits (MRLs). The procedure involves a modified quick, easy, cheap, efficient, rugged and safe (QuEChERS) method coupled to gas chromatography with tandem mass spectrometry (GC–MS/MS). In order to obtain lower limits of quantification (LOQs), an additional extract preconcentration step prior to their purification was introduced. Retention times of analytes were corrected using the Automatic Adjustment of Retention Time (AART) program, which further improved the efficiency and peak identification after changing the sample matrices. The methodology was validated in accordance with the EU 'SANTE' guide and the obtained LOQs were in the range of 0.63 µg kg−1 (fenazaquin) – 39 µg kg−1 (imazalil), with the coefficient of variability (CV) lower than 6 %. The recoveries were in the range of 82 % (etofenprox) – 112 % (captan) at two different spiked levels. The validated procedure has been successfully applied to the analysis of various fruit and vegetable samples with high water content. The MRLs were exceeded for captan (in cucumbers and Ligol apples), dimethoate (in courgettes), lambda-cyhalothrin (in parsley roots) and linuron (in carrots), while the rest of the samples do not pose a health risk.