Determination of Avermectin Residue in Earthworms by High Performance Liquid Chromatography

A method for determination of avermectin B1a in earthworms was established by high performance liquid chromatography (HPLC) with fluorescence detector. Homogenized earthworms sample was extracted by acetonitrile, and cleaned up on alumina B cartridge and C18 solid-phase cartridge, followed by derivatization with 1-methylimidazole (1-MIZ) and trifluoroacetic anhydride (TFAA), and analyzed by HPLC with fluorescence detector set at 365 nm excitation and 475 nm emission wavelengths. The limit of detection of the method is 0.5 ng·g-1. The average recoveries of avermectin were 104.8%, 86,6% and 83.0%, respectively in earthworm samples fortified at 5, 50, 500 ng·g-1 and the Coefficient of variation ranged from 2.99% to 7.34%.