Continuous detection of volatile aromatic, unsaturated or halogenated hydrocarbons in air by adsorption on Pt-electrodes and subsequent oxidative desorption

Many organic compounds such as benzene, its derivatives and simple halogena ted hydrocarbons cannot be detected by Usual amperometric sensors. Their de tection, however, is possible by means of their adsorption at a Pt-sensor e lectrode. The charge is automatically determined during a subsequent sweep to potentials above I V (RHE). It is corrected for oxygen adsorption and se rves as a measure for the substance concentration. A special potential prog ram serves to repeatedly strip the adsorbate from the surface, thus allowin g the continuous detection of such compounds [ I]. By a continuous impedanc e measurement, the amount of adsorbate is monitored during the adsorption p eriod. In this way, the adsorption period is finished at a preset, constant coverage and a linear dependence on concentration is obtained. Some exampl es for cross sensitivities are given, as well as ways to reduce them by usi ng appropriate potential programs. A negligible cross sensitivity of a tolu ene sensor towards CO (<3.5 X 10(-3), toluene = 1) is demonstrated which is important for the detection of BTX compounds in traffic.