Confirmation of eprinomectin, moxidectin, abamectin, doramectin, and ivermectin in beef liver by liquid chromatography/positive ion atmospheric pressure chemical ionization mass spectrometry

A liquid chromatographic (LC) multiresidue screening procedure was develope d for determination of eprinomectin, moxidectin, abamectin, doramectin, and ivermectin in beef liver at 0, 25, 50, and 100 ppb levels. A procedure usi ng low resolution LC/atmospheric pressure chemical ionization (APCI) mass s pectrometry (MS) was developed with further purification steps added to the quantitative LC method to confirm residues. Acetonitrile extracts of liver , prior to derivatization for LC analysis, were further purified by using a Cg solid-phase extraction cartridge and an alumina-B cartridge, The purifi ed extract was analyzed by injection into an LC/positive ion APCI MS. Ident ity of the compound was confirmed by comparison of its retention time and r elative intensity data with those of a standard or recovery from a fortifie d control liver sample, Anthelmintic drugs in acetonitrile extracts of live r containing eprinomectin, moxidectin, abamectin, doramectin, and ivermecti n at 25 ppb, the lowest level of fortification used in the LC determinative method, were successfully confirmed.