HPLC Determination of Prohibited Pesticides of Urea Derivatives in Corn Starch

Three prohibited pesticides of urea derivatives,i.e. chlorsulfuron,chlorofluazuron and chloroxuron,in corn starch were determined by HPLC. The pesticides in sample were extracted with methanol ultrasonically and the extract obtained was evaporated and blown to dryness with nitrogen. One mL of methanol was added to dissolve the residue and the solution was used for HPLC determination. The chromatographic column of ZORBAX Eclipse XDB-C18 (2.1 mm×150 mm,5 μm) was used as stationary phase,and mixtures of acetonitrile and water in different proportions were used as mobile phase in the gradient elutions. UV-detection at 220 ℃ with DAD was adopted in the determinations. Linear relationships between values of peak area and concentration of the pesticides were obtained in the same range of 0.2-100.0 mg·L-1 for all the 3 pesticides. Detection limits (S/N=3) found was 0.04 mg·kg-1 for chlorsulfuron,0.03 mg·kg-1 for chlorfluazuron and 0.01 mg·kg-1 for chloroxuron. Test for recovery and precision of the method were tested,giving values of average recovery (n=5) 92.0%,93.4% and 95.9%,and values of RSD′s (n=6) 3.5%,2.7% and 3.8% for the 3 pesticides respectively.