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Journal of agricultural and food chemistry

Enantioselective acute toxicity and bioaccumulation of benalaxyl in earthworm (Eisenia fedtia).


PMID 19694444

Abstract

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 LC(50) values of the R-(-)-form, rac-form, and S-(+)-form were 4.99, 5.08, and 6.66 microg/cm(2), respectively. After 72 h of exposure, the calculated LC(50) values were 1.23, 1.73, and 2.45 microg/cm(2), 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.

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