Determination of antimicrobial preservatives in pharmaceutical formulations using reverse-phase liquid chromatography.

A specific stability-indicating reverse-phase high-performance liquid chromatographic analytical method has been developed to quantitate the antimicrobial preservatives methylparaben, propylparaben, butylparaben, sorbic acid, and benzoic acid in a series of typical pharmaceutical formulations. The mobile phase of this system is a water-acetonitrile mixture, modified by various acids and buffers. The proportions of water and acetonitrile as well as the type and amounts of modifiers are varied in order to achieve optimum chromatography. This method has been used successfully to quantitate preservatives in solutions, suspensions, creams, lotions, and ointments, and can be readily adapted to routine automated assays, either for routine product evaluation or stability programs.