Plasma-polymerised organosiloxane thin films as selective gas sensors

By means of plasma polymerisation, thin films from siloxanes feeds [octamethylcyclotetrasiloxane (OMTS) and hexamethyldisiloxane (HMDSO)] were deposited onto single-crystal quartz resonators with a frequency of oscillation of 5 MHz, and the amount of adsorbed vapour, which is proportional to its volume concentration, was determined from the change in frequency. Selective sorption of inhalant anaesthetics was achieved by annealing quartz resonators covered by poly(OMTS) at 100-200 degrees C. The measurement was carrried out in a dynamic regime in such a way that the vapour of the substance to be measured was brought to the resonators by a carrier gas (air, N-2, N2O). The concentration of anaesthetic vapour measured in the carrier gas varied from 0.25 to 5.0 vol.%, and in H2O vapour from 1% to 90%-relative humidity. The designed system can be applied in practice in anaesthesiology. (C) 1998 Elsevier Science S.A..