[Methods of determining admixtures in commercial preparations of tetracycline]

The results and conditions of separation and quantitative determination of the admixtures of epi- and anhydro-derivatives of tetracycline in its market products were compared and analyzed using the following chromatographic methods: chromatography in a thin layer of a sorbent in 2 modifications, circular paper chromatography, chromatography on a column of gel Sephadex G-25. The comparison of the results of the study provided recommendation of the column chromatography with gel Sephadex G-25 for separate or summation quantitative determination of 4-epitetracycline. The method of chromatography in a thin layer of a sorbent may be successfully used for semiquantitative determination of the admixture levels in tetracycline market drugs.