Improved method for determination of abamectin and ivermectin in cattle plasma

A liquid chromatographic (LC) method was developed for determination of aba mectin (ABM) and ivermectin (IVM) in cattle plasma. The sample was extracte d with acetonitrile and cleaned up on an alumina column. After conversion t o stable fluorescent derivative with trifluoroacetic anhydride and N-methyl imidazole, the sample was analyzed by LC with fluorescence detection (Ex 36 5 nm and Em 475 nm). Doramectin was used as an internal standard. Recoverie s ranged from 91.2 to 100.7% for IVM and from 87.0 to 98.7% for ABM, with 1 -50 ng/mL fortified samples. The coefficients of variation were < 10.1%. Th e limit of detection was 0.02 ng/mL for ABM and IVM in 1.0 mL samples.