‘pH-Chromatography’ of some Amphoteric Antibiotics

Abstract

‘pH-CHROMATOGRAPHY’ is a paper chromatography method which can be used for simultaneous determination of the ionic character of antibiotics and of suitable pH values for their extraction¹. The pH-chromatogram of an antibiotic is obtained by chromatographing on a series of strips of chromatographic papers buffered to pH values from 2 to 10. For the development of the strips by the ascending technique an organic solvent saturated with water is used. A suitable solvent is chosen by determining the solubility of the antibiotic being studied by paper chromatography². In our reports on the pH-chromatography of antibiotics^1,3 we described three types of pH-chromatograms, depending on the ionic character of antibiotics: (1) R _F values of pH-chromatograms of antibiotics of acidic nature give S-shaped curves, the maxima of which lie in the acidic range ; with increasing pH values the R _F values diminish. (2) The R _F values of pH-chromatograms of antibiotics of basic character give S-shaped curves of a reverse character ; the maximum of the curves being in the basic and the minimum in the acidic range, respectively. (3) pH-chromatograms of neutral antibiotics have practically the same R _F values along the whole range of pH values, giving a straight line parallel with the starting points.