Wide-scope analysis of veterinary drug and pesticide residues in animal feed by liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry

Abstract

A fast and generic method has been developed for the simultaneous monitoring of >250 pesticides and veterinary drugs (VDs) in animal feed. A 'dilute-and-shoot' extraction with water and acetonitrile (1% formic acid) followed by a clean-up step with Florisil cartridges was applied. The extracts were analysed by ultra-high performance liquid chromatography coupled to hybrid analyser quadrupole-time-of-flight mass spectrometry using both positive and negative electrospray ionisation. The detection of the residues was accomplished by retention time and accurate mass using an in-house database. The identification of the detected compounds was carried out by searching of fragment ions for each compound and isotopic pattern. The optimised method was validated and recoveries ranged from 60% to 120% at three concentrations (10, 50 and 100 μg kg(-1)) for 30%, 68% and 80% of compounds, respectively, included in the database (364) in chicken feed. Document SANCO 12495/2011 and Directive 2002/657/CE were used as guidelines for method validation. Intra-day and inter-day precisions, expressed as relative standard deviations, were lower than 20% for more than 90% of compounds. The limits of quantification ranged from 4 to 200 μg kg(-1) for most analytes, which are sufficient to verify compliance of products with legal tolerances. The applicability of the procedure was further tested on different types of feed (chicken, hen, rabbit and horse feed), evaluating recoveries and repeatability. Finally, the method was applied to the analysis of 18 feed samples, detecting some VDs (sulfadiazine, trimethoprim, robenidin and monensin Na) and only one pesticide (chlorpyrifos).