Automated method for determination of penicillins, cephalosporins, and penicillinases

The microiodometric assay of Novick for penicillinase was adapted to the Technicon Autoanalyzer system. With this automated method, it is possible to analyze almost 60 samples per hr. Two different procedures are described: in the first, the samples were incubated with substrate in the machine under standardized conditions; in the second, samples were incubated outside the Autoanalyzer and assayed at intervals for penicilloic acid. As little as 5 mum penicilloic acid could easily be detected in a sample of 0.4 ml. The reproducibility was very good. The hydrolysis of penicillin in a suspension of nongrowing bacteria as well as in a growing culture could also be followed. The automated method has been used both for kinetic studies and in screening for activity in eluates from column chromatography experiments.