Multiresidue analysis of avermectins in bovine liver by immunoaffinity column cleanup procedure and liquid chromatography with fluorescence detector

A multiresidue liquid chromatography (LC) method was developed to detect avermectin, ivermectin, doramectin, and eprinomectin simultaneously in bovine liver. The extracted samples were cleaned up by an immunoaffinity column, which was prepared by coupling anti-avermectin polyclonal antibody with CNBr-activated Sepharose 4B. The dynamic column capacities of avermectin, ivermectin, doramectin, and eprinomectin were 3531, 3542, 3543, and 3284 nglmL gel, respectively. The eluate was evaporated to dryness, and residues were derivatized and determined by LC with fluorescence detector set at 365 nm excitation and 465 nm emission wavelengths. Recoveries ranged from 79.3 to 115.9% with coefficients of variation of 1.1-19.4% when avermectin, ivermectin, doramectin, and eprinomectin were spiked at levels of 5-100 ng/g. The limit of quantitation of the method was 2 ng/g for each drug.