DETERMINATION OF PESTICIDE RESIDUES IN WHEAT GRAIN BY THE GC-MS/MS METHOD AFTER THEIR ISOLATION USING THE MODIFIED QUECHERS METHOD AND HYPER CROSS-LINKED POLYSTYRENE AT THE PURIFICATION STAGE

Hyper cross-linked polystyrene was proposed for purification of extracts after sample preparation by QuEChERS method using multicomponent dispersive solid-phase extraction for determination of 19 pesticide residues in wheat grain by gas chromatography with tandem mass spectrometric detection. Sample preparation included extraction with water and acetonitrile and further purification of the extracts using hyper cross-linked polystyrene. The method provided quantitative separation of pesticides (degrees of separation ranged from 66 to 100 %). Pesticides were identified by selected transitions in multiple reaction monitoring mode. Determination was carried out by matrix graduation method and the limits of detection and determination were 0.03-0.3 and 0.1-1.0 µg/kg, respectively. The analysis of contaminated wheat samples showed that the results satisfactorily coincide with the data obtained by the classical QuEChERS method for determination of pesticide residues in agricultural products.