Multiresidue method for the determination of avermectin and moxidectin residues in the liver using HPLC with fluorescence detection.

A method using high-performance liquid chromatography (HPLC) and fluorescence detection is presented for the simultaneous determination of the antiparasitic agents avermectins (abamectin, ivermectin and doramectin) and moxidectin in liver. Samples are extracted using acetonitrile and cleaned up using solid phase extraction on a C18 column, followed by derivatization with trifluoroacetic anhydride. The samples are injected without further cleanup into the HPLC column and any avermectins or moxidectin present are detected using fluorescence detector set at 361 nm excitation and 465 nm emission wavelengths. The limits of quantification are below the stipulated EU Maximum Residue Limit for each of the avermectins and moxidectin. Mean recoveries in bovine liver ranged from 77.5 to 90.8%, with a RSD from 2.7 to 7.7%. The procedure provides a rapid, reliable and sensitive method for determinating avermectin and moxidectin residues in liver of different species (cattle, sheep, pigs). It is also applicable to muscle without modification.