COLLABORATIVE STUDY OF THE ANALYSIS OF TETRACYCLINE BY LIQUID-CHROMATOGRAPHY ON POLY(STYRENE-DIVINYLBENZENE)

A previously developed method for the analysis of tetracycline by liqu id chromatography on poly(styrene-divinylbenzene) packing materials wa s examined in a collaborative study involving five laboratories and a total of seven columns. The main compound and the impurities of three tetracycline samples were determined. An analysis of variance, conside ring each column as a different laboratory, proved absence of consiste nt laboratory bias. The laboratory-sample interaction was significant. Estimates for the repeatability and the reproducibility of the method , expressed as relative standard deviations of the result of the deter mination of tetracycline, were calculated to be 0.9 and 1.5% respectiv ely.