A new electrochemical analyser for nitric oxide and nitrogen dioxide

Individual sensors employing Teflon-bonded diffusion electrodes have been developed to measure nitric oxide and nitrogen dioxide separately, simultaneously, and continuously at part-permillion levels. The NO sensor was biased at 1.5V and that for NO(2) at 0.8V, both relative to the hydrogen electrode. The crucial factor in the virtual elimination of response from carbon monoxide, a relatively abundant air-pollutant, was the use of gold electrodes for both detectors. At 0.8 V NO does not react on gold. Although NO(2) does oxidize at 1.5 V it was removed quantitatively from NO/NO(2) mixtures by triethanolamine on firebrick. The NO(2) reduction signal and the NO oxidation signal were stable and reproducible.