A highly sensitive NO2-selective optode membrane

A new NO2-sensitive polymeric optode membrane is introduced. It takes advan tage of the reactivity of NO2 with an aquacyanocobalt(III)-cobyrinate deriv ative. The detection mechanism leads to a protonation of the Nile Blue deri vative ETH 5418, which changes its visible spectrum thereby. The polymer la yer also contains the aquacyanocobalt(III)-cobyrinate derivative, which sig nificantly 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. A large variety of polymers and plasticizers were tested in order to achiev e 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. (C) 2000 Elsevier Science B.V. All righ ts reserved.