Enantioseparation and determination of indoxacarb in tobacco and soil by ultra-performance convergence chromatography with tandem mass spectrometry

In order to enantioseparate and analyze the indoxacarb in tobacco and soil, a method was proposed for the simultaneous enantiomeric analysis of indoxacarb in tobacco and soil using ultra-performance convergence chromatography with tandem mass spectrometry (UPC²-MS/MS). Sample preparation prior to UPC²-MS/MS analysis followed QuEChERS (quick, easy, cheap, effective, rugged and safe) procedure. The UPC²-MS/MS method used a Chiralcel IG-3 column with a mobile phase consisting of CO₂ and methanol. The extract was analyzed quantitatively by UPC²-MS/MS under the multiple reaction monitoring (MRM) mode, and the results were quantified by matrix matching standard working curve. The results showed that:1) The enantiomer of indoxacarb reached baseline separation, and the chiral separation time was only 5 minutes. 2) Under the optimal conditions, the recoveries for the enantiomers were 83.7%-96.6% with relative standard deviation(RSD) less than 6.0% at 2.5, 7.5 and 15.0 mg/kg levels. Good coefficients of determination (R² ≥ 0.993 2) were achieved for all studied enantiomers in the tobacco and soil in the concentration range of 50-1 000 ng/mL. The LOD for the enantiomers in tobacco and soil varied from 0.028 to 0.048 mg/kg, and the LOQ varied from 0.088 to 0.148 mg/kg. 3) Ten tobacco samples and ten soil samples were tested by this method, and only one soil sample was found to contain R-indoxacarb (1.05 mg/kg) and S-indoxacarb (0.88 mg/kg). The proposed method is green, convenient and reliable for the enantioselective determination of enantiomers of indoxacarb in tobacco and soil.