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

A previously developed method for the analysis of tetracycline by liquid chromatography on poly(styrene-divinylbenzene) packing materials was 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, considering each column as a different laboratory, proved absence of consistent 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 determination of tetracycline, were calculated to be 0.9 and 1.5% respectively.