Enantioselective determination of the insecticide indoxacarb in cucumber and tomato by chiral liquid chromatography-tandem mass spectrometry.

A convenient and precise chiral method was developed and validated for measuring indoxacarb enantiomers in cucumber and tomato using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with a reversed-phase Chiralpak AD-RH column. The target analytes were extracted by acetonitrile and then purified by solid phase extraction (SPE) using NH2 /Carb combined-cartridge. Parameters including the matrix effect, linearity, precision, accuracy, and stability were used. Then the proposed method was successfully applied to investigate the possible enantioselective degradation of rac-indoxacarb in cucumber and tomato under open conditions. The results indicated that the degradation of indoxacarb enantiomers followed first-order kinetics in cucumber and tomato. The half-lives of (+)-S-indoxacarb in cucumber and tomato were 3.0 and 5.9 days, respectively; while the (-)-R-indoxacarb were 7.3 and 12.2 days, respectively. The data of the half-lives showed that (+)-S-indoxacarb was preferentially degraded in cucumber and tomato. Moreover, indoxacarb degraded faster in cucumber than in tomato.