Improvement and extension to new analytes of a multi-residue method for the determination of pesticides in cereals and dry animal feed using gas chromatography–tandem quadrupole mass spectrometry revisited

This article describes a substantially improved multi-residue method for the determination of a large number of pesticides in cereal samples (wheat, rye, barley, oats, maze, buckwheat etc.) and various animal feeds. The sample preparation method and the GC–MS/MS acquisition method were modified to accommodate new complex cereal and feed matrices and to extend the existing analytical scope to 167 pesticides. The co-extractives were reduced by the joint use of primary secondary amine (PSA) and octadecyl (C18), 75 mg and 50 mg/1 mL of acetonitrile extract, in the presence of MgSO4, and thus the optimal recovery and analytical selectivity were obtained simultaneously. The new cleanup procedure was faster and easier to handle than our previously applied cleanup procedure. The overall recoveries of the pesticides from buckwheat and rye at the three spiking levels of 0.01, 0.05 and 0.25 mg kg−1 were 96 ± 9% with relative standard deviations of 10 ± 4% on average. At the lowest spiking level of 0.01 mg kg−1, 137 of 167 pesticide residues (82%) fulfilled the validation criteria with recoveries in the range of 70–120% and RSDs less or equal 20% whereas in the previous approach it was 93 out of 140 analytes (66%). The developed method was implemented in a routine analysis of approximately 900 real samples, providing an increased scope of the analysis, improved analytical performance parameters and improved ruggedness versus the previous approach. A total of 17% analyzed samples contained pesticide residues. There were 24 different compounds encountered in the samples, of which pirimiphos-methyl, tebuconazole, deltamethrin, and chlorpyrifos-methyl were the most frequent ones.

► GC–MS/MS-based method for trace analysis of multiple pesticides was established.
► Thorough optimization helped to tailor the method to cereals and feedingstaffs.
► The approach significantly improved analytical performance of the method.
► The method was used for analysis of many cereal and feed samples with success.