Determination of Carbamate Pesticides Residues in Vegetables by UPLC-MS/MS with QuEChERS Extraction

Vegetable samples were homogenized and kept at -20℃ separately for use as analytical samples. 10.00 g of the homogenized sample were mixed with 10 mL of a mixture of acetonitrile containing 1.3% (volume fraction) formic acid, and extracted ultrasonically for 20 min. After adding 8.2 g of anhydrous sodium sulfate (as dehydrator) and 3.0 g of sodium chloride (as salting-out agent), the mixture was centrifuged for 5 min. The supernatant was separated and preserved. The sample was extracted once more as described above. The supernatants were combined, and an aliquot of 2.0 mL was taken and purified by swirling with 0.4 g of PSA, 0.25 g of C₁₈ and 8.2 mg of GCB for 2 min, and then centrifuged for 2 min. The supernatant was taken and filtered through 0.22 μm filtering membrane. The filtrate was used as testing solution for determination of residual amounts of the 6 carbamate pesticides by UPLC-MS/MS. In UPLC separation, Agilent Poroshell 120 EC-C₁₈ column was used as stationary phase and mixtures in various ratios of (A) 20 mmol·L^-1 NH₄OAc solution (containing 1 mL of acetic acid perliter) and (B) acetonitrile were used as mobile phases in programed gradient elution. ESI and MRM mode were adopted in MS/MS. Linear relationships were found between values of peak areas of the 6 carbamate presticides and the respective mass concentrations in the same range of 0.200-100 μg·L^-1, with their detection limits (3S/N) in the range of 0.08-0.38 μg·kg^-1. Test for recovery was made by standard addition method, giving results in the range from 81.0% to 111%, and values of RSDs (n=6) ranged from 2.8% to 4.9%.