A reversed-phase simultaneous determination method for the enantiomers of carfentrazone-ethyl and its metabolite carfentrazone in agricultural and environmental samples was established using high-performance liquid chromatography-tandem mass spectrometry. A complete enantioseparation of carfentrazone-ethyl and its chiral metabolite carfentrazone enantiomers was obtained using a chiral column. The absolute configuration and specific optical rotation of carfentrazone-ethyl and carfentrazone enantiomers were first confirmed as peaks 1, 2, 3, and 4: S-(+)-carfentrazone, R-(-)-carfentrazone, S-(-)-carfentrazone-ethyl, and R-(+)-carfentrazone-ethyl, respectively. The specificity, matrix effect, linearity, precision, accuracy, and stability were surveyed to evaluate the feasibility of the method. The mean recovery was in the range of 77.5-102.8% with relative standard deviations of 0.4-9.8% for the samples. The limits of detection of the enantiomers were evaluated as 0.7 to 6.0 μg/kg, and the limits of quantification were 2.5 to 20 μg/kg. The stereoselective degradation of carfentrazone-ethyl and carfentrazone in rice plant was investigated, and there was no clear enantioselectivity for carfentrazone-ethyl. As for carfentrazone, the enantiomer fractions value reached 0.85 at 7 days after spraying. The developed method was simple and reliable enough for the corresponding risk assessment of carfentrazone-ethyl and its metabolite enantiomers in crop plants, cereal grains, and soil samples.
Keywords: absolute configuration; carfentrazone-ethyl; chirality; enantioseparation; metabolite.
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