Analysis of penicillin mixtures by paper chromatography of the hydroxamic acid derivatives

Abstract

A rapid method that is independent of biological assays, suitable as a routine procedure for estimating one or more species of penicillin in a mixture and requires less than 8 hrs. for completion, is described. It is based on the fact that the relatively stable hydroxamic acid derivatives of the various penicillins show different partition coefficients between isopropyl ether-isopropyl alcohol and phthalate buffer, at a given pH, and can therefore be separated by paper chromatography. A novel apparatus for use with volatile solvents and heavily buffered papers is described. A direct, qualitative result is obtained by developing the chromatograms with dilute ferric chloride soln. A quantitative result is attained by extracting the Fe complexes of the various hydroxamic acids with butyl alcohol, measuring the degree of extinction in a colorimeter and reading the penicillin concn. from standard curves.