Multi-residue screening method of acidic pesticides in agricultural products by liquid chromatography/time of flight mass spectrometry

Abstract

A simple and rapid screening method of 95 acidic pesticides in agricultural products was developed. As acidic pesticides adsorb on the primary secondary amine mini-column with fatty acids which become interfering peaks during GC/MS analysis, they were not included in multi-residue analysis entailing PSA clean-up. In this study, the intermediate extracted solutions before PSA clean-up were analyzed by LC/TOF-MS. Accurate mass measurement of TOF-MS enabled the detection of molecular ions and fragment ions with high selectivity. Mean recoveries of 95 pesticides added to 6 agricultural products at 0.1 μg/g were 49–127% with RSD <20%. Limits of quantitation were 0.01–0.02 μg/g for 95 pesticides. The method was applied to 140 samples, and 2,4-D from lemon and orange, fluazifop from baby kidney bean, dichlorprop from apple were detected, respectively, at 0.02–0.03 μg/g below MRLs. The proposed method showed good sensitivity for 95 acidic pesticides and enabled rapid screening in combination with our multi-residue method targeted to 520 pesticides.