Method validation and application of a selective multiresidue analysis of highly polar pesticides in food matrices using hydrophilic interaction liquid chromatography and mass spectrometry.

The effectiveness of highly polar pesticides in agriculture is well known, while their low costs contribute to the frequent use. On the other hand, their physicochemical properties make their analytical determination a challenging task. The aim of this study is the evaluation of a methanol-based extraction method with a simple clean-up step using a selective multiresidue LC-MS/MS method for 14 highly polar pesticides and their metabolites. For the clean-up step, several sorbents from different brands, with diverse mechanisms of action, were tested. Different dilution factors for the final extract were also evaluated in order to check the impact on the matrix effects. The optimised method was validated for matrices from different commodity groups. Recovery studies performed with grapes, lettuce, orange, oat and soya beans showed absolute average recoveries in the range 70-120% with relative standard deviation values below 20% for almost all the pesticides tested. The matrix effects observed were very different in each matrix and for each individual pesticide evaluated. Therefore, isotopically labeled procedural internal standards were used for all compounds in order to correct for recovery and matrix effects. Method Limits of Quantification for most analyte-matrix combinations were 0.02 or 0.05 mg kg-1. The final optimised method appeared to be reproducible and robust in routine analysis of a wide variety of fruits, vegetables and cereals. Monitoring results are presented to show the occurrence of the compounds studied in real samples. The residue concentrations ranged from 0.023 to 30 mg kg-1 for the analytes detected.