Benzalkonium Chloride (BAC) refers to a series of quaternary ammonium chloride homologues. The pervasive use of BAC in consumer products results from its antiseptic and antifungal properties with widespread applications ranging from cleaning products and disinfectants to sanitizing wipes and ophthalmic solutions. Because of its extensive use, BAC has been the subject of numerous studies, including the evaluation of the reactivity of BAC with ocular tissue and the study of worldwide municipal wastewater, which found BAC to be the most prevalent quaternary ammonium compound in wastewater, with concentrations ranging between 200 and 300 mg/L.
The USP method for the quantitation of BAC utilizes a 10 μm particle size cyano column (L10) for the separation of the BAC homologues. The isocratic method uses acetonitrile and 0.1M sodium acetate (pH 5.0) as mobile phases, resulting in a separation requiring between 15 and 30 minutes. In addition to long analysis times, these separations suffer from reproducibility issues due to the traditionally poor chemical and mechanical stability of the cyano stationary phases. Here we present an alternative method employing a Charged Surface Hybrid (CSH) C18 stationary phase under UPLC® conditions, resulting in improved peak shapes with significant reductions in both analysis time and solvent consumption. Additionally, we include an example of this method that is transferred to conditions using the XSelect CSH C18 X P 2.5 μm stationary phase (UPLC and HPLC), demonstrating the ability to transfer methods across different instrument platforms.