No abstract

Residues of 14 kinds of b-lactam and macrolide antibiotics in bovine muscles were extracted with acetonitrile and the extract was partitioned with n-hexane to remove fat. High-performance liquid chromatography was carried out on a TSK-gel ODS-80TM column using gradient elution with acetonitrileῌ0.05ΐ trifluoroacetic acid and the drugs were quantitated by diode array detection. The recoveries of the drugs from bovine muscles spiked at 0.1 ppm were over 63ΐ and each quantitation limit was 0.04 ppm.

Abamectin, doramectin, eprinomectin, ivermectin, milbemectin, and moxidectin in bovine muscle and liver were extracted with acetonitrile. The extracts were partitioned with n-hexane and then evaporated to dryness. The residue was cleaned up on Bond Elute NH2 cartridge, and the drugs were eluted from the cartridge with methanol–ethyl acetate (3 + 7). The eluate was evaporated to dryness, and residues were derivatized with N,N-dimethyl-formamide–acetic anhyride-1-methylimidazole. The derivatives were determined by liquid chromatography with fluorescence detection. Recoveries of the 6 drugs were 79.6–63.8% in muscle and 71.6–60.6% in liver at 0.01 ppm levels. The quantitation limits were 5 ppb for each drug.