文摘
The enantioselectivities of individual enantiomers of benalaxyl in acute toxicity and bioaccumulation in earthworm (Eisenia fedtia) were studied. The acute toxicity was tested by paper contact test. After 48 h of exposure, the calculated LC50 values of the R-(−)-form, rac-form, and S-(+)-form were 4.99, 5.08, and 6.66 μg/cm2, respectively. After 72 h of exposure, the calculated LC50 values were 1.23, 1.73, and 2.45 μg/cm2, respectively. Therefore, the acute toxicity of benalaxyl enantiomers was enantioselective. A method for determining residues of the two enantiomers of benalaxyl in earthworm tissue by high-performance liquid chromatography based on cellulose tri-(3,5-dimethylphenyl-carbamate) chiral stationary phase was developed. During the bioaccumulation experiment, the enantiomer fraction in earthworm tissue was maintained approximately at 0.6, whereas enantiomer fraction in spiked soil was maintained at 0.5; in other words, the bioaccumulation of benalaxyl was enantioselective in earthworm tissue. Peak-shaped accumulation curves were observed for both enantiomers, and the calculated biota to soil accumulations (kg dry kg−1 wet weight) at steady state were below 1 for both enantiomers. During the elimination experiment, 79.0% of R-(−)-enantiomer and 89.6% of S-(+)-enantiomer in earthworm tissue were eliminated within 2 days.