Quantification and screening of pesticide residues in food by gas chromatography–exact mass time-of-flight mass spectrometry

A gas chromatography–exact mass time-of-flight mass spectrometry (GC–TOF-MS) method has been developed for the quantification of approximately one hundred pesticides in baby food, pear and lettuce samples. Prior to analysis, co-extractives were removed from acetonitrile:toluene (80:20) extracts using dispersive solid-phase extraction with primary secondary amine (50 mg) and carbon sorbent (50 mg). The concentration of pesticides in the extracts was measured using an extracted mass chromatogram window of 0.05 Th. Samples spiked with pesticides at 0.01 and 0.1 mg kg−1 yielded average recoveries in the range of 70–109% with relative standard deviations less than 26% and displayed good linearity for the majority of the analytes. The method was applied to the screening of pear and lettuce samples for pesticide residues. Targeted quantification and exact mass peak detection, deconvolution and library searching packages were used successfully to detect and identify incurred residues present in the samples at concentrations above 0.01 mg kg−1. The new feature dynamic range enhancement, improved mass accuracy, and hence detection and quantification of the analytes across the concentration range studied.