HPLC Determination of Residual Thiabendazole in Milk and Milk Products

Sample of milk or milk products was saponified with KOH solution by refluxing for 40 min,and the solution obtained was extracted with ethyl acetate to transfer the residual thiabendazole (TBZ in short) into the organic phase,which was washed with KOH solution for purification.The ethylacetate solution was evaporated to near dryness at temperature not over 45 ℃,and the residue was taken and made up to 1.0 mL,which was used for LC determination.ODS C18 chromatographic column was used as stationary phase,and mixture of methanol and water (70+30) was used as mobile phase.Peak area of TBZ at tR of 4.43 min was measured with DAD,and external standard method was adopted in HPLC determination.Detection limit (3S/N) of the method found was 0.02 mg·kg-1.Tests for recovery and precision at 3 concentration levels were made,giving values of recovery ranged from 94.5%-98.6%,and values of RSD′s (n=10) in the range from 1.3%-4.2%.