Multi-residue analysis of avermectins in swine liver by immunoaffinity extraction and liquid chromatography–mass spectrometry

A multi-residue LC–MS method was developed to determine avermectin residues in swine liver. Abamectin and ivermectin (22,23-dihydroabamectin) were extracted, and cleaned up by immunoaffinty columns with immobilized anti-avermectin polyclonal antibodies. The cleaned samples were separated by high-performance liquid chromatography (HPLC) with a C8 column and determined by negative-ion atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) using selective ion monitoring (SIM) of [M-H]−. Recoveries of abamectin and ivermectin from fortified samples at 5–100 μg kg−1 levels ranged from 74 to 94% and from 65 to 87%, respectively. The limits of detection were 5 μg of abamectin or ivermectin in 1 kg sample.