Residue analysis of fungicide boscalid in cucumbers following applications of boscalid 50% water dispersible granule

This study determined the residue of fungicide boscalid in/on cucumbers following three applications of boscalid 50% water dispersible granule (WG). The fungicide was applied to cucumbers at two rates, 0.5 and 0.83 kg a.i./ha. Samples were collected at 0, 1, 2, 3, 4, 6, 7, 10, 12, 15, 18, and 21 d after the last application. The sample was extracted with methanol/H2O/2 N HCl (70:25:5, v/v) and n-hexane and subject to GC analysis. Residues of boscalid were determined by GC/μ-ECD with DB-5 capillary column. Recoveries of boscalid in/on cucumbers ranged from 86.0 to 103.6% and the relative standard deviation (RSD) ranged from 1.2 to 4.8%. The limit of quantification was 0.01 μg/mL (S/N>10). This analytical method was applied to study the dissipation of boscalid in/on cucumbers. The results indicated that the residues of boscalid were declined in/on cucumbers with time. Only 5 and 17% of the initial deposits were found in/on the cucumbers 6 d after the last application at the low and high dose, respectively.