Determination of multiresidue of avermectins in bovine liver by an indirect competitive ELISA

An ELISA was developed to detect multiresidues of avermectins (AVMs) including abamectin (ABM), ivermectin (IVM), and eprinomectin (EPR) in bovine liver. The modified ABM, 4'-O-succinoyl-ABM was conjugated to bovine serum albumin as the immunogen for the preparation of polyclonal antibodies to AVMs and conjugated to ovalbumin as the coating antigen for the ELISA. Serum with the highest antibody titers to AVMs, which had a cross-reactivity of 100% with ABM, 145.4% with EPR, and 25% for IVM, was selected for the development of an indirect competitive ELISA. The ELISA could detect ABM, IVM, and EPR residues in bovine liver tissues, with a limit of quantitation of 1.06 ng/mL for all three AVMs. Optimal pH, ion strength, organic solvent, and duration of incubations were investigated to increase the sensitivity of the ELISA. Recoveries of these drugs ranged from 53.8% to 80.6% with inter-assay coefficients of variation (CV) of 3.4-17.9% and intra-assay CV of 5.5-14.7%. Analysis results of field samples by the ELISA were consistent with those by a previously developed HPLC method. The ELISA can be used as a rapid method for screening of AVMs residues in bovine liver.