IMPROVED SEPARATION OF ERYTHROMYCIN ON AGED REVERSED-PHASE COLUMNS .2.

In a first paper it was reported that chromatography of erythromycin derivatives on short chain reversed-phases could be improved by conditioning the column by heating it at 120-degrees-C after it had been flushed with a mobile phase methanol-water-1M phosphoric acid (50:45:5). Besides an improvement of the resolution and symmetry of the peaks, a reduction of the retention times was observed. In this paper the effect of conditioning was examined using C18 reversed-phases. Here also an improvement of the chromatography of erythromycin derivatives was achieved but reduction of retention times was only observed on a low loaded phase. It is believed that the reduction of the retention times is merely a secundary effect of the conditioning, which removes part of the bonded phase from the less stable stationary phases. The improvement of the chromatography must be related to modifications at the silica gel surface.