Liquid chromatography for the quantitative analysis of antibiotics--some applications using poly(styrene-divinylbenzene).

Problems arising from the microbiological assay of antibiotics are discussed. The existence of several systems to express the potency leads to confusion. The use of potency to express the content of bulk products can lead to difficulties in the interpretation of the content of pharmaceutical preparations. Such problems can be avoided if the content of antibiotics is expressed as percentage weight in weight. This involves the application of selective assay methods such as liquid chromatography. The reproducibility of liquid chromatography depends largely on the quality of the stationary phase. Use of poly(styrene-divinylbenzene) as the stationary phase can lead to good reproducibility as is reported for erythromycin and for the tetracyclines, of which minocycline is discussed as an example.