Determination of the fungicide kresoxim-methyl in grape juices using square-wave voltammetry and a boron-doped diamond electrode

•Kresoxim-methyl was determined by square-wave voltammetry in grape juice.•A boron-doped diamond electrode enabled irreversible oxidation of kresoxim-methyl.•A possible mechanism for the oxidation of kresoxim-methyl is proposed.•Conditions were adjusted for trace level determination of kresoxim-methyl.

A square-wave voltammetric method for the determination of kresoxim-methyl in grape juices was developed using the nanocrystalline boron-doped diamond electrode where an irreversible oxidation occurred. Measurements were made through the anodic scan from +1000 to +1750 mV (Maximum at +1420 mV) in pH 4.0 acetate buffer 0.050 mol L−1. Linear signal response (R2 > 0.999) expanded form the 8.7 × 10−7 mol L−1 (0.27 mg L−1) up to 3.4 × 10−5 mol L−1 (11 mg L−1). The method was applied in the analysis of analyte fortified grape juices. Solid phase extraction allowed pre-concentration of the analyte and eliminated interferences imposed by sample matrix. Recoveries from 91.6% to 105.3% were found and agreed with results achieved using high performance liquid chromatography.

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