Residue screening in apple, grape and wine food samples for seven new pesticides using HPLC with UV detection. An application to trifloxystrobin dissipation in grape and wine

Abstract

A new analytical procedure was developed and validated, using liquid chromatography, for simultaneous determination of seven new pesticides belonging to different chemical classes (azoles, strobilurines, benzoylureas, and a new oxazolidinedione) in apple, grape and wine food samples. Solvent extraction of pesticides was performed using a cyclohexane-dichloromethane (9 + 1 v/v) mixture and the extract was cleaned-up by solid-phase extraction (SPE) using silica cartridges and elution with tetrahydrofurane. Separation of pesticides flusilazole, fenbuconazole, diniconazole, tebufenozide, famoxadone, trifloxystrobin and flufenoxuron was performed by gradient elution High-Performance Liquid Chromatography (HPLC) with a microbore Hypersil HS C18 column in 35 min total time, using mixtures of acetonitrile-water as the mobile phase. Pesticides were detected and quantified at 210 nm with a variable-wavelength UV detector. Recoveries of pesticides from spiked samples, at 0.05-2.0 mg kg-1 for apple and grape and at 0.025-0.250 mg L-1 for wine, ranged from 82 to 107% for apple and grape and from 87% to 106% for wine with RSD 12%. The limits of quantification (LOQs) of the method, as a signal to noise ratio equalled 10, ranged from 0.02 to 0.10 mg kg-1 for apple and grape and from 0.005 to 0.02 mg L-1 for wine samples. The uncertainty associated with the analytical methodology, estimated using the 'bottom-up' approach, was lower than 12.8% for all pesticides and matrices tested. The proposed methodology was applied for the evaluation of trifloxystrobin residue levels in grapes exposed to field treatments and in the must and wine produced from them.