Improvement in the multiresidue liquid chromatographic analysis of residues of mono- and dibasic penicillins in bovine muscle tissues

A recently developed multiresidue method using gradient liquid chromatograp hic conditions for analysis of residues of beta-lactam drugs in bovine musc le tissues after precolumn derivatization with acetic anhydride was modifie d to permit isocratic analysis. The modification included replacing the acy lating reagent, acetic anhydride, with benzoic anhydride and increasing sam ple size for extraction from 2 to 3 g. The modifications have reduced analy sis time per sample from >1 h to about 22 min without loss in detection sen sititivities for the beta-lactams, resulting in a significant increase in t he number of samples that can be analyzed in 1 day from 1 to 8. The modific ations make the multiresidue LC method more suitable than the original meth od for use in regulatory programs for routine analysis of these veterinary drug residues in bovine muscle tissues.