Simultaneous enantioselective determination of isocarbophos and its main metabolite isocarbophos oxon in rice, soil, and water by chiral liquid chromatography and tandem mass spectrometry

An efficient enantioselective method for the simultaneous determination of isocarbophos and its main metabolite isocarbophos oxon in rice, soil, and water was developed using liquid chromatography with tandem mass spectrometry. The enantioseparation was performed on a Chiralpak AD-3R column at 30 degrees C using gradient elution. Target compounds were extracted from soil and rice using acetonitrile with omission of a clean-up procedure, while a C-18 solid-phase extraction column was used for water samples. Quantification was achieved using matrix-matched calibration. The overall mean recoveries for isocarbophos and isocarbophos oxon enantiomers from the five matrices were 89.7-103 and 90.1-98.7%, with relative standard deviations of 2.1-5.4 and 2.5-4.7%, respectively. Moreover, the absolute configurations of isocarbophos oxon enantiomers were determined by liquid chromatography with tandem mass spectrometry through incubation of each isocarbophos enantiomer in soil, the first eluting enantiomer being confirmed as (R)-(-)-isocarbophos oxon. The proposed method was applied to real soil samples and satisfactory results were obtained.