Guanidinium-Based Potentiometric SO2 Gas Sensor

An SO 2 gas sensor was developed by using a hydrogen sulfite-selective electrode positioned behind a gas-permeable membrane (GPM). The hydrogen sulfite-selective electrode was prepared by incorporating a multicyclic guanidinium ionophore in a plasticized poly(vinyl chloride) membrane. This gas sensor presents important advantages over the conventional Severinghaus-type SO 2 gas sensor that contains a pH electrode immersed in an internal solution behind the GPM. The Severinghaus gas sensor suffers interferences from weak acids that can cross the GPM as gases and change the pH of the internal solution. In contrast, in the proposed sensor, the excellent selectivity of the HSO 3 - electrode and the ability of the GPM to discriminate gaseous from nongaseous species combine to generate the most selective potentiometric SO 2 gas sensor reported to date.