MICROELECTROCHEMICAL SENSOR FOR NITROGEN-OXIDES

A sensor for nitrogen oxides is presented based on the Back Cell(TM) sensor design. This unique sensor design allows response times many times faster than those of conventional amperometric ps sensors to be achieved. Conventional amperometric NO sensors operating at an NO oxidation potential suffer from interference caused by oxidation of NO2, which occurs in the same potential range. In the present sensing scheme, the sensor is operated at two different potentials. At the first potential, both NO and NO2 are oxidized; the second potential produces a reduction current proportional to NO2 concentration alone. This signal can be subtracted from the first signal to obtain an interference-free measurement of the NO concentration. In practice, the oxidation current when both NO and NO2 are present is higher than the sum of their individual currents, indicating a synergistic effect between the two gases. This type of NO(x) sensor may find application in environmental monitoring.