A comparative study of solid and liquid inner contact benzalkonium chloride ion-selective electrode membranes

► A new approach for determination of low concentrations of the BzCl preservative is presented. ► Two new, a solid and a liquid contact, electrodes for benzalkonium chloride were designed. ► A comparison of the electrodes characteristics was performed. ► Solid contact electrode (SC ISE) showed lower detection limit because of diminished ion fluxes. ► Electrodes showed accurate and reproducible detection of BzCl in preparations as eye and ear drops.