Liquid chromatography in pharmaceutical analysis III: separation of diuretic-antihypertensive mixtures.

High-pressure liquid chromatography was used to optimize the resolution of therapeutic agents commonly found in antihypertensive preparations. Seven widely prescribed drugs were investigated. The compounds were chromatographed on reversed-phase octadecyltrichlorosilane (C18) or diphenyldichlorosilane (phenyl) columns, using mixtures of acetonitrile or absolute methanol and distilled water buffered with ammonium acetate, ammonium chloride, or ammonium carbonate. By calculating approximate resolution values, the separation of selected drug mixtures can be predicted.