DEVELOPMENT OF AN ANALYTICAL METHOD FOR M ETHOPRENE IN RICE BY HPLC

A new analytical method was developed for the determination of methopr ene, an insecticide, in rice. Methoprene was extracted with n-hexane f rom powdered samples. The concentrated n-hexane extract was purified b y distillation in a Dean-Stark apparatus for 1.5 hr, and then cleaned- up with a Sep-pak Florisil cartridge. The eluate was used as test solu tion. Methoprene in the test solution was determined by UV-HPLC. The c hromatography was performed on an Inertsil ODS-2 column with a mobile phase consisting of acetonitrile and water (9: 1). Recovery of methopr ene was in the range of 80 approximately 86% when the compound was spi ked at the concentration of 0.5 ppm in rice. The detection limit of me thoprene by the proposed method was 0.02 ppm. No methoprene was detect ed in any of 10 samples imported from Thailand, the United States, and P.R. China during November and December, 1993.