Galvanic-type electrochemical sensor for determining the content of hydrohalogens in the air

A galvanic-type amperometric sensor based on manganese dioxide gas-diffusion electrodes has been created for determining the concentration of hydrohalogens (HCl, HBr, HF) in the air. The sensor works on the principle of solid phase reduction of manganese dioxide at the indicator electrode with simultaneous absorption of hydrohalogens from the air by the electrolyte film and oxidation of non-stoichiometric manganese dioxide at the auxiliary electrode. Technical data of the sensor developed have been determined. At a ground current of ±0.25 μA and current signal normalized to 2.0 μA per 1 ppm hydrohalogens, the sensor resolution amounted to less than 0.3 ppm. The sensor life is set by the load of manganese dioxide at the indicator electrode and service conditions. The sensor storage life exceeds 3 years. After the concentration of hydrohalogens has been measured, a ground current of the reverse sign appears to regenerate the sensor life. The sensors are operable over the temperature range from −30 to +50 °C and the relative humidity range from 15 to 98%.