Abstract
An analytical method for the residue of sethoxydim [(±)2-(1-ethoxyiminobutyl)-5-[2-(ethylthio) propyl]-3-hydroxycyclohex-2-enone, STM] in crops was established using high-performance liquid chromatograph (HPLC). A chopped sample was extracted with 50% aqueous methanol (including 5% Na2S2O3) and STM was transferred to n-hexane. After extracting with 0.1N NaOH, the extract was acidified by HCl. STM in the acidic solution was extracted with dichloromethane. After concentrating to a certain volume, the solution (10μl) was injected into HPLC. HPLC analysis was carried out on a Zorbax SIL column with a 0.5%MeOH/CH2Cl2 elution and with a UV detection of 254nm. The lowest detection limit was 0.02ppm and the recovery was 79.3-83.6%. No STM residue was detected in any crops examined, indicating that the STM was rapidly degraded to metabolites.
