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

摘要

Many organic compounds such as benzene, its derivatives and simple halogenated hydrocarbons cannot be detected by Usual amperometric sensors. Their detection, however, is possible by means of their adsorption at a Pt-sensor electrode. The charge is automatically determined during a subsequent sweep to potentials above I V (RHE). It is corrected for oxygen adsorption and serves as a measure for the substance concentration. A special potential program serves to repeatedly strip the adsorbate from the surface, thus allowing the continuous detection of such compounds [ I]. By a continuous impedance measurement, the amount of adsorbate is monitored during the adsorption period. In this way, the adsorption period is finished at a preset, constant coverage and a linear dependence on concentration is obtained. Some examples for cross sensitivities are given, as well as ways to reduce them by using appropriate potential programs. A negligible cross sensitivity of a toluene sensor towards CO (<3.5 X 10(-3), toluene = 1) is demonstrated which is important for the detection of BTX compounds in traffic. [References: 25]