Guanidinium-based potentiometric SO2 gas sensor

An SO2 gas sensor was developed by using a hydrogen sulfite-selective elect rode positioned behind a gas-perme able membrane (GPM). The hydrogen sulfit e-selective electrode was prepared by incorporating a multicyclic guanidini um ionophore in a plasticized poly(vinyl chloride) membrane. This gas senso r presents important advantages over the conventional Severinghaus-type SO2 gas sensor that contains a pH electrode immersed in an internal solation b ehind 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 sol ution. In contrast, in the proposed sensor, the excellent selectivity of th e HSO3- electrode and the ability of the GPM to discriminate gaseous from n ongaseous species combine to generate the most selective potentiometric SO2 gas sensor reported to date.