Determination of diquat residues in rape seeds

摘要

AbstractA method for the determination of diquat residues in rape seeds has been developed. It is based on the original procedure of Calderbank, Morgan and Yuen1as modified by Kirsten2for diquat residues in potato tubers, which includes acid hydrolysis, ion exchange clean‐up, colour formation and spectrophotometry. When applied to rape seeds the background was too high. Ion pair extraction with bromthymol blue in dichloromethane removed most interfering substances. Measurement of absorbance at three wavelengths 10 nm apart increased the specificity further.Because of varying recoveries from rape seeds (range 35‐60) in the procedure isotope dilution analysis was applied to each sample. The limit of detectability at 40‐50 recovery in a 20 g sample is 0.07 mg/kg and in a 50 g sample 0.03 mg/kg. The application to field trials is illust