Rapid Determination of Cyromazine Residue in Vegetables by Cation Exchange High Performance Liquid Chromatography

A total of 10 g of vegetable sample was taken, and 20 mL of acetic acid-acetonitrile mixed solution at volume ratio of 1∶99 was added. The mixture was shaken for extraction for 20 min, and 6 g of anhydrous magnesium sulfate was added. The mixture was shaken for 5 min, and centrifuged for 2 min. An aliquot (4 mL) of the supernatant was taken and passed through an activated amino solid phase extraction column, and all the effluent was collected. The column was eluted by 2 mL of acetonitrile-toluene mixed solution at volume ratio of 3∶1, and the eluate was collected and combined with the above mentioned effluent. The obtained solution was blown to near dryness by nitrogen at 40 ℃, and re-dissolved in 1.0 mL of the mixed solution (mobile phase) of 20 mmol·L⁻¹ sodium acetate solution containing 0.2% (volume fraction) acetic acid and acetonitrile at volume ratio of 65∶35 by vortex for 1 min. After passing through a 0.22 μm filter membrane, the filtrate was analyzed by high performance liquid chromatograph. The mobile phase was used for isocratic elution separation of the target in the filtrate on the ZORBAX 300-SCX strong cation exchange chromatographic column, with the external standard method for quantitative analysis. It was shown that linear relationship between values of the mass concentration and peak area of cyromazine was kept in the range of 0.02-2.00 mg·L⁻¹, with detection limit (3S/N) of 0.006 mg·kg⁻¹. Test for recovery was made according to the standard addition method, giving recoveries in the range of 83.6%-90.5%, and RSDs (n=6) of the determined values ranged from 1.5% to 9.0%. The proposed method was applied to the analysis of 43 batches of vegetable samples, with the detection rate of 28% for cyromazine. The detection amounts of cyromazine in 3 batches of cowpeas exceeded the limit specified in GB 2763—2021.