Potentiometric ion-selective electrodes for determination of cyclopentolate hydrochloride and phenylephrine hydrochloride in their challenging ophthalmic formulation

Introduction of potentiometric ion-selective electrodes (ISEs) opened a new bright area in pharmaceutical analysis acknowledged as being an eco-friendly, simple, and energy-saving technique that is well-suited with microfabrication. In this contribution, potentiometric ISEs were employed as an alternative green analytical tool with the crucial goal of expanding the effective application of the potentiometric sensors in different disciplines of drug-stability studies and quality-control investigations. Four novel cyclopentolate hydrochloride and phenylephrine hydrochloride selective membrane sensors were constructed and evaluated. Sensors' fabrication was achieved using potassium tetrakis (4-chlorophenyl) borate, a cationic exchanger, in a polyvinyl chloride polymeric matrix plasticized with 2-nitrophenyl octyl ether and using 2-hydroxy propyl-beta-cyclodextrin as an ionophore. A comparative potentiometric study was implemented using two designs of ISEs; a conventional liquid inner contact and a glassy carbon solid-contact one. Using solid-contact ISEs, detection limit was substantially decreased and the discriminative ability in the presence of the most interfering substances was enhanced. This permits simultaneous estimation of both drugs, in spite of their similar ionic characteristics, abolishing the need for any pretreatment or separation steps in their challenging combined ophthalmic formulation as well as in rabbit aqueous humor and in the presence of their degradation products.