A highly sensitive NO2-selective optode membrane

A new NO2-sensitive polymeric optode membrane is introduced. It takes advantage of the reactivity of NO2 with an aquacyanocobalt(III)-cobyrinate derivative. The detection mechanism leads to a protonation of the Nile Blue derivative ETH 5418, which changes its visible spectrum thereby. The polymer layer also contains the aquacyanocobalt(III)-cobyrinate derivative, which significantly reduces the response time and improves the operational lifetime of the sensor compared to a blank membrane. No cross-sensitivity to NO, CO, CO2 and only a small interference by SO2 was observed. e variety of polymers and plasticizers were tested in order to achieve resistance to high temperature and to improve the lifetime of the sensor. Until now, the plasticized poly(vinylchloride) membranes still remain the material of choice in view of a good compromise between stability, response time and solubility of components.