Potentiometric Analysis of Benzalkonium Chloride with 3D Printed Ion-Selective Membranes
Nguyen H. B. Ho, Dalton Lee Glasco, Jeffrey G. Bell
Abstract
Benzalkonium (BA + ) chloride is one of the most common preservatives used in prescription-based and over-the-counter eye drops. Knowing the concentration of BA + in eye drops is important for both quality control (at the pharmaceutical preparation stage) and human health (ocular toxicity has been linked to BA + use). This paper describes the design and fabrication of a benzalkonium-selective potentiometric sensor for the determination of BA + in ophthalmic solutions. The sensor is composed of a 3D-printed ion-selective membrane (ISM) that selectively measures BA + in the presence of potentially interfering ions routinely found in ophthalmic formulations (i.e., Mg 2+ , Ca 2+ , Na + and K + ). The 3D printed BA + -ion-selective electrodes (ISEs) produced a Nernstian response of 55 mV/Decade across a range of 1.0 mM to 31.0 μ M BA + along with an LOD of 8 μ M, which covers the relevant concentration range found in ophthalmic solutions. The 3D printed BA + -ISEs proved to be highly stable with an average drift of 205 μ V/hr. Successful measurement of BA + in diluted ophthalmic solutions was completed from 100–500 μ M. The mass production capability afforded by 3D-printing offers a unique and intriguing fabrication protocol for developing low-cost sensors which could be incorporated quickly and seamlessly by pharmaceutical companies or community-based pharmacies.