Enantioseparation and Quantification of Chiral Pesticide Indoxacarb Residues in Tea by UHPLC-Q-TOF/MS

In order to meet the need of enantioseparation and quantification of chiral pesticide indoxacarb residue determination in tea, an effective reversed phase chiral analytical method was developed for the resolution and determination of indoxacarb enantiomers in tea by ultra- high pressure liquid chromatography-quadrupole-time of flight mass spectrometry （UHPLC-Q-TOF/MS）. Indoxacarb enantiomers were extracted by acetonitrile followed by Florisil and GCB mix-column cleanup from tea, then separated on a Lux 3 μ Cellulose1 column with V（0.10% formic acid）∶V（methanol）=15∶85 as the mobile phases at 0.40 mL/min. Over the concentrations in the range of 0.002 5—0.600 mg/L for both of indoxacarb enabtiomers, the correlation coefficients (r) of the calibration curves are 0.997 3 and 0.993 1 for each other, and the estimated limits of detection(LODs) are 0.001 mg/L. The average recoveries of two indoxacarb enantiomers in green tea at three spiked concentration levels(0.01, 0.10 and 1.00 mg/kg) range from 80.75% to 101.69% with relative standard deviations (RSDs) lower than 15% (n=6). The limits of quantitation (LOQs) of two indoxacarb enabtiomers are 0.002 5 mg/kg in green tea. The result shows that this method is reliable, accurate and suitable for the residue determination of indoxacarb enantiomers in tea.