Polymeric hydrogel integrated paper-based potentiometric ion-sensing device for the determination of sodium ions in human urine.

A paper-based potentiometric sensor integrated with a polymeric hydrogel has been developed for sodium ion (Na) determination in human urine. The construction of an all-solid-state ion selective electrode (s-ISE) and an all-solid-state reference electrode (s-RE) on a photo paper substrate was achieved using an inkjet printing method. For s-ISE fabrication, carbon nanotubes (CNTs) and gold nanoparticles (AuNPs) were printed on the substrate as a nanocomposite solid contact. A polymeric hydrogel containing lithium acetate (CHCOOLi) was then prepared and used as an intermediate layer to improve the adhesion between the ion selective membrane (ISM) and the AuNP/CNT solid contact, leading to enhanced detection sensitivity. The printed s-RE consisted of a pseudo silver/silver chloride electrode (p-Ag/AgCl) coated with a polymeric hydrogel containing KCl to improve the potential stability of the sensor. Under the optimal conditions, the hydrogel-integrated paper-based potentiometric sensor provided a response toward Na over a linear range of 10 M to 1 M with a near Nernstian slope of 56.42 ± 0.68 mV per decade. This sensor exhibited fast response, good sensitivity, and reasonable selectivity for Na measurement. Furthermore, the developed sensor was effectively applied for the detection of Na in urine samples with high accuracy. The presented work can be considered as a good addition to the growing field of potentiometric analytical platforms suitable for large-scale production using inkjet printing technology.