Solid-contact ion-selective electrode with stable internal electrode

A new substrate for the construction of solid contact ion-selective electrodes (SC-ISEs) based on a conductive and porous carbon matrix is presented. The conductive characteristics of the substrate, its controlled porosity in combination with the use of a non-aqueous second kind internal reference element offers considerable advantages over the symmetrical configurations. The SC-ISEs presented here are very easy to construct, can be made very small in size, and can be used in high pressure environments. At the same time it is shown that the characteristics of the two electrodes constructed (K+ and NO−3) exhibit at least the same performance characteristics as the best commercially available symmetric counterparts. The potentiometric response is monitored over a period of one month with excellent results with regard to drift, base line stability, response time, selectivity, and detection limit.