COLLABORATIVE STUDY OF THE ANALYSIS OF CHLORTETRACYCLINE BY LIQUID-CHROMATOGRAPHY ON OCTYLSILYL SILICA-GEL

An established method for the analysis of chlortetracycline by liquid chromatography using octylsilylated silica gel as the stationary phase was examined in a multicentre study involving five laboratories and a total of six columns. Three chlortetracycline hydrochloride samples w ere analysed. The main component and the impurities were determined. A n analysis of variance, treating each column as a different laboratory , showed an absence of consistent between-laboratory bias and the pres ence of a significant laboratory-sample interaction. The repeatability and the reproducibility of the method, expressed as relative standard deviations of the result of the determination of chlortetracycline hy drochloride, were calculated to be 0.9% and 1.1% respectively.