Simultaneous Determination of Methyl, Ethyl, Propyl, and Butyl 4-Hydroxybenzoates and 4-Hydroxybenzoic Acid in Liquid Antacid Formulations by Gas Chromatography

□ An isothermal chromatographic (GC) method employing an SE-30 column and flame-ionization detection has been developed for the simultaneous assay of methyl, ethyl, propyl, and butyl 4-hydroxybenzoates and 4-hydroxybenzoic acid in liquid antacid formulations. The method, which uses a silica column chromatographic cleanup step prior to GC, is specific for the compounds with respect to possible degradation products, impurities, and excipients.