Multicomponent analysis of some environmentally important gases using semiconductor tin oxide sensors

Alumina sapphire based, tin oxide thick film sensors, undoped and doped with precious metals (gold, platinum and palladium) were prepared and annealed at different temperatures, before being examined for determination of carbon monoxide, nitrogen dioxide and methane as single gas or in binary mixtures. Gold-doped tin oxide sensor was found to respond to both CO and NO2 separately more rapidly than undoped sensor, however, the simultaneous determination of both gases in their binary mixture was not possible. Therefore, in the binary mixture an amperometric sensor was used for the determination of CO while the SnO2 sensor was used for NO. The multicomponent determination of CO and NO was achieved using a set of two platinum-doped tin oxide sensors annealed at 600 degreesC. one at a working temperature of 150 degreesC selective for NO2, and the other at 300 degreesC selective for CO. On the other hand, the multicomponent determination of CH4 and NO2, was achieved using a set of two tin oxide sensors, one is doped with Pd and working at 300 degreesC selective for methane and the other doped with Pt and working at 150 degreesC selective for nitrogen dioxide. (C) 2001 Elsevier Science B.V. All rights reserved.