Erythromycin series. V. Quantitative analysis of cladinose and methylcladinoside by densitometry of thin-layer chromatograms.

A direct, quantitative, thin-layer chromatographic method is described for the determination of sugar cladinose and methylcladinoside in the presence of other acid-degradation products of the antibiotics erythromycin oxime and erythromycyl-amine. Cladinose and methylcladinoside are separated from compounds which cause interference on pre-coated silica gel F254 plates, and are measured directly on the thin-layer plate using a densitometer. Standard graphs obtained for cladinose and methylcladinoside show a linear relation between the square root of the peak area and the logarithm of the amount of substance present in the spot, as well as between the square of the area and the logarithm of the amount. This method is very successful in stability studies on the antibiotics erythromycin oxime and erythromycylamine in an acid medium. The technique seems to be particularly useful in instances in which the usual analytical methods either cannot be applied or can be applied only with difficulty.