Simple Cleanup Procedure for Analysis of Buprofezin Residues and Its Metabolite in Crops by Gas Chromatography

Abstract

Abstract An analytical method for determining residues of buprofezin (2-tert-butylimino-3-isopropyl-5-phenylperhydro- 1,3,5-thiadiazin-4-one) and its p-hydroxy metabolite (p-hydroxybuprofezin, one of its major metabolites in plants) in crops such as rice, citrus, and tomato was investigated. On the basis of the basicity of these compounds, a liquid–liquid partition, rather than column chromatography, was used for cleanup. Samples were extracted with acetone or methanol, and the concentrated extracts were partitioned between n-hexane and 1N HCI. After the aqueous layer was neutralized with 10N NaOH, the compounds were extracted with n-hexane, and the extract was analyzed with a gas-liquid chromatograph (GLC) equipped with an alkali flame ionization detector (AFID). p-Hydroxy- buprofezin was detected after acetylation with acetic anhydride–pyridine because its peak was broad and showed tailing on GLC. The limits of detection for buprofezin and p-hydroxybuprofezin were 0.005 ppm in hulled rice, citrus flesh, and tomato and 0.01 ppm in rice straw and citrus peel. Recoveries of both compounds fortified at 0.1 or 0.2 ppm were 75–97%.