Enantioselective degradation of diclofop-methyl in cole (Brassica chinensis L.)

Abstract

The stereoselective degradation of the racemic diclofop-methyl and its chiral degradation product, diclofop (the hydrolysate of diclofop-methyl), in cole has been investigated. Both enantiomers of diclofop-methyl and diclofop were extracted by organic solvent and detected by chiral high-performance liquid chromatography–diode array detector (DAD). Cellulose-tris-(3,5-dimethylphenylcarbamate)-based chiral column was used for the chiral separation of the four enantiomers applying a mixture of n -hexane and 2-propanol (98:2) concluding 0.1% TFA as mobile phase at a flow rate of 1.0 mL/min. The assay method was linear over a range of concentrations (0.5–250 mg L −1 ), and the mean recovery was more than 60% for all the enantiomers. The limit of detection for all the enantiomers was 0.2 μg g −1 in plant. Racemic diclofop-methyl was foliar sprayed to cole. Stereoselective behaviour was observed in the diclofop-methyl degradation process. The ( S )-diclofop-methyl dissipated faster than ( R )-diclofop-methyl. In the case of diclofop, the generation and degradation rates of ( S )-enantiomer were higher than ( R )-enantiomer in the plant.