Planar chromatography for screening of ivermectin residues in swine and cattle tissues.

A method was developed for qualitative detection of ivermectin residues. It involves extraction of 1 g tissue sample with 5 mL acetonitrile and C18 solid-phase extraction. After derivatization with trifluoroacetic anhydride, the extract is purified again on the same but previously reconditioned C18 column. The eluate is evaporated, and the residue is diluted in methanol. The method allows detection of residues in swine and cattle meat, liver, and fat at levels as low as 5 micrograms/kg.