Separation and toxicity of salithion enantiomers

Abstract

Enantioseletive toxicities of chiral pesticides have become an environmental concern recently. In this study, we evaluated the enantiomeric separation of salithion on a suite of commercial chiral columns and assessed the toxicity of enantiomers toward butyrylcholinesterase and Daphnia magna. Satisfactory separations of salithion enantiomers could be achieved on all tested columns, that is, Chiralcel OD, Chiralcel OJ, and Chiralpak AD column. However, the Chiralpak AD column offered the best separation and was chosen to prepare micro-scale of pure salithion enantiomers for subsequent bioassays. The first and second enantiomers eluted on the Chiralpak AD column were further confirmed to be (-)-S-salithion and (+)-R-salithion, respectively. The half inhibition concentrations to butyrylcholinesterase of racemate, (+)-R-salithion, and (-)-S-salithion were 33.09, 2.92, and 15.60 mg/l, respectively, showing (+)-R-enantiomer being about 5.0 times more potent than its (-)-S-form. However, the median lethal concentrations (96 h) of racemate, (+)-R-salithion, and (-)-S-salithion toward D. magna were 3.54, 1.10, and 0.36 microg/l, respectively, suggesting that (-)-S-salithion was about 3.0 times more toxic than (+)-R-form. Racemic salithion was less toxic than either of the enantiomers in both bioassays, suggesting that antagonistic interactions might occur between the enantiomers during the toxication action. This work reveals that the toxicity of salithion toward butyrylcholinesterase and D. magna is enantioselective, and this factor should be taken into consideration in the environmental risk assessment of salithion.

Enantiomeric determination of azole antifungals in wastewater and sludge by liquid chromatography–tandem mass spectrometry

“…Many commonly used azole antifungals, for example miconazole and ketoconazole, are chiral compounds with one or more chiral centers; also they are usually administered as racemates [29,30]. Enantiomeric separation of some pharmacological and agrochemical azole fungicides by use of capillary electrophoresis, high-performance liquid chromatography, and supercritical-fluid chromatography coupled with ultraviolet or fluorescence detection has been reported [18,29,[31][32][33][34].…”

Synthesis and application of a novel molecularly imprinted polymer‐coated stir bar for microextraction of triazole fungicides in soil

“…Information about the residues in agricultural products and environment is important in assessment of the potential risk associated with the exposure. Several methods for monitoring triazole fungicides have been reported, including gas chromatography (GC) [28], highperformance liquid chromatography (HPLC) [29,30], liquid chromatography coupled with mass spectrometry (LC-MS). However, the complex sample matrices in biological and environmental samples often affect the analytical accuracy.…”

Enantioselective determination of triazole fungicide tebuconazole in vegetables, fruits, soil and water by chiral liquid chromatography/tandem mass spectrometry

“…However, so far as we know, enantioselective determination of tebuconazole enantiomers in environmental and food matrices is currently not available. In the past, the vast majority enantioseparation methods of tebuconazole were performed by chiral HPLC with UV detection [27][28][29][30][31][32][33][34]. Moreover, the chiral separation of tebuconazole was also employed by GC-MS technique equipped with a BGB 172 chiral column; however, the two enantiomers were only partially separated [35].…”