Benzalkonium chloride (BAK) is a common preservative composed of quaternary ammonium compounds with 8–18 carbon alkyl chains, mainly C12, C14, and C16 homologs. Because BAK can adsorb to surfaces, this study highlights the challenges of predicting adsorption behavior and the importance of conducting a vial compatibility assessment early in HPLC method development for dilute solutions of BAK and analytes with similar physicochemical properties.
