Determination of benzalkonium chloride in aqueous ophthalmic preparations by high-performance liquid chromatography.

A high-performance liquid chromatographic method is described for the determination of homologues of benzalkonium chloride in aqueous ophthalmic preparations. The technique involves direct injection of the sample on a 5-microns Spherisorb-CN column. The mobile phase is acetonitrile-triethylamine (0.1%, v/v) in water (pH 2.5; 40:60, v/v). Detection is carried out at 215 nm. The method is rapid, specific, reproducible and simple, and is especially useful for the assay of this preservative in stability studies and quality control procedures.