Method development and validation for cyprodinil and fludioxonil in blueberries by solid-phase microextraction gas chromatography, and their degradation kinetics

A method of analysis for residues of cyprodinil and fludioxonil in blueberries was developed. Fungicide residues were determined by solid-phase microextraction coupled to GC with nitrogen-phosphorous detection. The effect of pH values and fibre coatings was studied. The solid-phase microextraction fibre coating selected was 100 µm polydimethylsiloxane. The method was selective, with adequate precision and high accuracy and sensitivity. Apparent recoveries ranged within the 99-101% range for cyprodinil and the 98-100% range for fludioxonil; LODs and LOQs were 1.2 and 3.9 µg/kg for cyprodinil and 0.4 and 1.3 µg/kg for fludioxonil, respectively. Statistical parameters indicated a matrix effect; consequently, calibration was performed on spiked samples. Degradation of cyprodinil and fludioxonil was studied in a blueberry field located in Concordia (Argentina), with fruit from Emerald and Jewel varieties. The degradation of these fungicides in both blueberry varieties studied followed first-order rate kinetics for both fungicides, and the half-life for cyprodinil was 2.2 and 3.4 days for Emerald and Jewel cultivars, respectively, and for fludioxonil was 12.7 and 16.3 days, respectively.