Detection of Volatile Organic Solvents Using Potentiodynamic Gas Sensors

Abstract

Amperometric electrochemical gas sensors have the advantage of combining good sensitivity and selectivity at relatively low cost. However, their use is restricted to the detection of gases that are very reactive at potentials positive of that at which oxygen is reduced. We describe here a new detection method for less reactive species such as benzene and halogenated hydrocarbons, which cannot be directly oxidized. Instead, the species is continuously adsorbed at a potential below 0.5 V and then oxidized at potentials where oxygen coadsorbs. The oxidation current is corrected for the oxygen adsorption current by performing an additional potential cycle, in which no adsorption is allowed to occur. We have so far obtained sensitivities in the lower ppm range for benzene, toluene, tetrachloroethene, epichlorohydrin, and vinyl acetate; for saturated halogenated hydrocarbons such as CFCl 3, it is still below 1000 ppm.