MEASUREMENTS OF VOCS IN SOILS THROUGH A TIN OXIDE MULTISENSOR SYSTEM

A tin oxide multisensor with 15 sensor elements has been prepared usin g the r.f. reactive sputtering technique. Some components of this mult isensor have been doped with Pt, Pd and Al by sputtering. Each sensor has been characterized by electrical measurements for various volatile organic compounds (VOCs) in a concentration range from 50 to 500 ppm in synthetic air at 300 degrees C. The best response has been obtained by Pt and Pd doped sensors for the oxygenated gaseous compounds, but for all gases tested a good recognition is shown. For the concentratio n range used it has been possible to detect the threshold limit values (TLV) for airborne contaminants of toluene, octane and methyl-ethyl-k etone. The influence of the oxygen species (O- and O-2(-)), ionosorbed on the sensing surface, on the VOCs detection is also discussed. (C) 1997 Elsevier Science S.A.