Determination of Residual Amounts of Seven Carbamate Pesticides in Vegetables by HPLC after Pretreatment of MWCNTs-MSPD

A method was developed for determination of seven carbamate pesticides, including aldicarb sulfone, methomyl, 3-hydroxycarbofuran, aldicarb, carbofuran, carbaryl and isoprocarb in vegetables by MWCNTs-MSPD-HPLC. Sample was homogenized with activated MWCNTs and anhydrous magnesium sulfate in a mortar, then the mixture was packed into a column, which was eluted with 20 mL of acetonitrile. The eluent was analyzed by HPLC. RRHD SB-C₁₈ chromatographic column was used as stationary phase, and the mixture of acetonitrile and water with various volume ratios was used as mobile phase for gradient elution. The seven pesticides separated were determined at detection wavelength of 220 nm (for carbaryl), 230 nm (for methomyl) and 200 nm (for the other five pesticides). Under the optimized working conditions, the retention times of the 7 pesticides were 3.625, 4.297, 6.153, 12.686, 17.265, 18.780 and 21.075 min. The results showed that linearity relationships between mass concentrations of the 7 pesticides and their corresponding chromatographic peak areas were kept in the same range of 0.025-5.00 mg·L^-1, with detection limits (3S/N) in the range of 0.0027-0.0110 mg·kg^-1. The spiked recovery test was made on the blank spinach sample at three concentration levels, giving recoveries ranged from 68.8% to 108%, with RSDs (n=5) in the range of 0.90%-7.5%. Six vegetables were analyzed by the prescribed method, the methomyl was detected in Chinese cabbage and cabbage, carbaryl was detected in lentil, and their contents were all within the limits specified in GB 2763-2014. This method was extended for the analysis of the seven carbamate pesticides in fruit samples, and the results of tests for precision and recovery both met the requirements of pesticide residue analysis.