Eletrochemical reduction of patulin and 5-hydroxymethylfurfural in both neutral and acid non-aqueous media. Their electroanalytical determination in apple juices

The electro-reduction of patulin mycotoxin and 5-hydroxymethylfurfural at glassy carbon electrodes in acetonitrile +0.1 mol L−1 tetrabutylammonium perchlorate, in both the absence and the presence of different aliquots of trifluoroacetic acid is reported. 5-hydroxymethylfurfural is the most common interference in the determination of patulin in products derived from apples. The electrochemical techniques were cyclic and square wave voltammetries, and controlled potential bulk electrolysis. The number of electrons exchanged in the patulin electro-reduction of n=1 could be inferred from controlled potential bulk electrolysis measurements. Ultraviolet-visible and infrared spectroscopies were used to identify patulin electro-reduction product/s. A value of (2.1±0.1)×10−5 cm2 s−1 for the patulin diffusion coefficient was calculated from convoluted cyclic voltammograms. A method based on square wave voltammetry was developed for the quantitative determination of patulin in both fresh, and commercial apple juices in the presence of 5-hydroxymethylfurfural. Calibration curves obtained from solutions of the commercial reagent, and commercial apple juices were linear in the range from 3.0×10−7 to 2.2×10−5 mol L−1. The lowest concentration measured experimentally for a signal to noise ratio of 3:1 was 3×10−7 mol L−1 (45 ppb) and a recovery percent of 84% was determined for commercial apple juices. This electroanalytical methodology appears as a good screening method for the determination of patulin in apple juices.