Chiral pyrethroid insecticide fenpropathrin and its metabolite: enantiomeric separation and pharmacokinetic degradation in soils by reverse-phase high-performance liquid chromatography

Abstract

The enantiomeric separation of fenpropathrin enantiomers on Lux Cellulose-1, Lux Cellulose-3 and Chiralpak IC chiral columns as well as enantioselective degradation of fenpropathrin in soil were investigated by reverse-phase high-performance liquid chromatography (RP-HPLC). The effects of the chiral stationary phase, mobile phase component, mobile phase ratio, temperature and thermodynamic parameters on resolution were carefully evaluated. Fenpropathrin enantiomers achieve a baseline separation (R_s = 2.30) on the Lux Cellulose-3 column with a mobile phase of methanol/water at a ratio of 85/15. Partial separations were achieved on Lux Cellulose-1 and Chiralpak IC columns with maximum R_s = 1.01 and R_s = 0.64, respectively. Enantioselective degradation of fenpropathrin enantiomers in soil was investigated based on the proposed separation method. The half-life (t_1/2) of S-fenpropathrin and R-fenpropathrin was 17.8 days and 12.6 days, respectively, indicating that the degradation of fenpropathrin in soil was enantioselective, with R-fenpropathrin preferentially degraded. Furthermore, the formation and degradation of 3-PBA, the main metabolite of fenpropathrin, were also investigated in three soils. Soil microorganisms were confirmed as the main factor that is responsible for enantioselective degradation of fenpropathrin enantiomers in soil. Such results provide a new approach for fenpropathrin enantiomer separation and contribute to a comprehensive risk assessment of fenpropathrin at the enantiomer level.