Stability enhancement of all-solid-state H+ISEs with cross-linked silicon-urethane matrices

An all-solid-state hydrogen-ion-selective electrode (ASHISE) was fabricated using the polymer hybrid membrane. Polymer membranes composed of Tecoflex polyurethane (TPU), polyvinyl chloride (PVC), silicon rubber (SR), and additives (KT rho ClPB, DOA, and TDDA) were cast on a carbon rod. The TPU/SR hybrid membrane exhibited a longer lifetime and a higher sensitivity in the sensing of the H+ ion compared to conventional TPU/PVC and PVC/SR hybrid membranes. Moreover, the addition of SiCl4 to TPU-based matrices enhanced the potentiometric response and ISE stability, due to the chemical bonding between Si and C=O in urethane, in which the cross-linking configuration was confirmed by DSC, FT-IR, and XPS experiments. TPU/SR membranes containing SiCl4 were rendered more stable and showed a pH response over a wide range (i.e., pH 2 - 11.5) with the slope of 60 +/- 2 mV/pH for more than four months. The ASHISE exhibited a small interfering potential variation in the wide range of the salt concentration (from 1.0 x 10(-6) M up to 0.1 M). The ASHISE showed a result comparable to a commercial clinical blood analyzer.