Rapid HPLC for quantitation of 4 kinds of avermectin residues in milk.

Avermectins were simply extracted with acetonitrile from milk.The sample solution was diluted with water and mini triethylamine.Avermectins were selectively concentrated by one 500 mg C18 cartridge.The elution was evaporated to dryness and derivatized,and then was determined by HPLC with fluorescence detection.The results showed that the concentrations of the four drugs were linearly correlated with their peak areas and the coefficient ≥0.99.The average recoveries of 4 target drugs range from 70.2% to 110.4% when spiked 2-1 000 μg/kg.The intra-coefficients of variation were in the range of 3.9%-8.2% and the inter-coefficients of variation were in the range of 5.1%-8.2%.The limit of detection was 0.5,0.5,0.4 and 0.2 μg/kg for eprinomectin,avermectin,doramectin and ivermectin,respectively,when calculated with 3 S/N.And the quantitation limit was 1.8,1.6,1.3 and 0.8 μg/kg,respectively.The most significant aspect of the present study was the much simplified sample preparation procedure.Only one reverse SPE without additional cleanup method was used for preparing samples.It is a rapid,specific,and sensitive method for determination of avermectin residues in milk.