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An isocratic liquid chromatographic method with UV detection at 215 nm, which is suitable for the analysis of azithromycin (AZT) in bulk samples, is described. AZT is separated from its synthesis intermediates and a degradation product as well as from six unknown impurities on an XTerra RP18 column at 70 degrees C using a mobile phase consisting of acetonitrile-pH 6.5 0.2M K2HPO4-water (35:10:55, v/v/v) at 1.0 mL/min. The XTerra stationary phase contains methyl groups that are incorporated in the bulk structure of the material. This allows for special selectivities. Robustness is evaluated by a full factorial design experiment. The method shows good selectivity, repeatability, linearity, and sensitivity.

SummaryA selective, repeatable, and robust isocratic liquid chromatographic method has been developed for the analysis of bulk samples of roxithromycin, a semi-synthetic macrohde antibiotic. The method involves the use of XTerra RP18 as stationary phase and acetonitrile-2.0 M (NH4)2HPO+ pH 6. 4-water, 25:30:45, (v/v) as mobile phase, delivered at a flow rate of 1.0 mL min 1. Detection was by UVabsorbance at 215 nm. Sufficient separation of roxithromycin from its homolog containing one more methyleneoxy group (roxithromycin G) and from other related substances was achieved. The robustness of the method was evaluated by means of a full-factorial experimental design.

Amoxycillin products were evaluated for quality by liquid chromatography at the Drug Analysis and Research Unit (DARU), University of Nairobi. Thirty three of these were capsule formulations and 24 were dry suspensions. Three capsule formulations failed the limits on content. The amoxycillin content in one suspension product was below the limit, while in two other products it dropped below 80% on storage at 25°C for 7 days.