Enantioselective Degradation and Chiral Stability of Profenophos in Soils

Profenophos, which has one chiral center and exists as two enantiomers, is a widely used organophosphorus insecticide. In this paper, the degradation of (±)-profenophos and (+)-profenophos in five soils was investigated using enantioselective high-performance liquid chromatography (HPLC). Our results showed that profenophos was degraded fast in soils with half-lives ranging from 4.2 h to 495.1 h. Further chiral analysis demonstrated the occurrence of enantioselectivity during the degradation of (±)-profenophos. Also, it was observed obviously that different enantioselectivities were showed in different soils. In Tianjin and Hubei alkaline soils, the (+)-enantiomer was degraded faster than the (-)-enantiomer. However, in Baoding alkaline soil both enantiomers were degraded at similar rates, and in Hubei and Guangdong acidic soils the enantioselectivity was reversed. In order to evaluate the effects of soil pH on the enantioselective degradation of profenophos, a Tianjin alkaline soil was acidified to pH 5.53 and the degradation of profenophos in this soil resulted in slower degradation rate and similar enantioselectivity. At last, during the degradation of enantiomer pure (+)-profenophos, no enantiomerization was observed in both nonsterilized and sterilized soils.