Influence of Soil Properties on the Enantioselective Dissipation of the Herbicide Lactofen in Soils
2009
Diao, Jinling | Lv, Chunguang | Wang, Xinquan | Dang, Ziheng | Zhu, Wentao | Zhou, Zhiqiang
A scheme was developed to elucidate the dissipation behaviors of the two enantiomers of the herbicide lactofen in soils using a normal-phase high-performance liquid chromatograph (HPLC) with UV detector and a column with a cellulose-tri-(3,5-dimethylphenylcarbamate)-based chiral stationary phase (CDMPC-CSP). Eight soils with a wide range of soil properties were studied. Racemic and the enantiopure (S)-(+)- and (R)-(-)-lactofen were incubated under aerobic and anaerobic conditions. The data from sterilized controls indicated that the dissipation of lactofen was biological. The dissipation was shown to be enantioselective with (S)-(+)-enantiomer being degraded faster than the (R)-(-)-enantiomer, resulting in residues enriched with (R)-(-)-lactofen when the racemic compound was incubated. Lactofen was configurationally stable in soil, showing no interconversion of (S)-(+)- to (R)-(-)- enantiomer and vice versa. Significant correlations of the enantioselectivity, expressed as ES = (k(S) - k(R))/(k(S) + k(R)) of lactofen with soil pH were observed under aerobic and anaerobic conditions. In addition, we found that the enantioselectivity correlated with the soil texture rather than the organic carbon.
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