DEVELOPMENT OF NOX GAS SENSORS BASED ON NITRATE-SELECTIVE POLYPYRROLEELECTRODES

A nitrate-selective polypyrrole-based electrode was used in the develo pment of NOx sensors. The nitrate-selective film was prepared by elect ropolymerizing pyrrole in presence of a nitrate salt. This resulted in a film that responded to nitrate in buffered media with near-Nernstia n slopes and excellent reproducibility. This electrode was incorporate d into a gas-sensing arrangement where it was immersed in a buffered c ompartment and separated from an acidified sample solution by a gas-pe rmeable membrane. Additions of nitrite to the acidified solution resul ted in the production of NOx, which can cross the gas-permeable membra ne into the buffered internal filling solution where it is trapped as nitrate and sensed by the nitrate-selective polypyrrole electrode. Thi s sensor arrangement resulted in detection limits in the mu M range an d had excellent selectivity characteristics.