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Platinum Metals Rev., 2000, 44, (2), 57

Detecting Gas Emissions with an Electronic Nose

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Gas emissions inside cars, caused by the release of volatile organic compounds (VOCs) from the interior trim materials, such as leather or plastics, contribute greatly to their internal air pollution. When the VOCs condense on surfaces, they leave an oily film, visible as fogged windscreens. Leather produces gas emissions, which can be high enough to cause nuisance and discomfort Existing methods of analysing such emissions are a DIN standard fogging test and tests for total VOCs using a gas chromatography-flame ionisation detector (GC-FID) or a GC-mass spectrometer (MS). However, these give inconsistent readings, are time consuming and in the DIN test only one material at a time can be measured.

Now researchers in Sweden have utilised a semiconductor gas sensor array which is combined with a pattern recognition routine, an “electronic nose”, to detect gas emissions from the leather used in cars (E.-L. Kalman, A. Löfvendahl, F. Winquist and I. Lundström, Anal. Chim. Acta, 2000, 403, (1-2), 31-38).

Aimed at mimicking the human olfactory system, the electronic nose is an analyser which can recognise, classify and quantify gaseous emissions and odours. The sensor array consists of 10 metal-oxide semiconductor field-effect transistors (MOSFETs) with gates of thin platinum, iridium and palladium of different thicknesses and combinations operated at two different temperatures, and five sensors based on semiconducting metal oxides (MOS).

Sensor array data gave similar and additional information to GC-MS. The electronic nose could also detect deviating leather samples with unusual gaseous emissions. The method is rapid, simple and inexpensive and while having problems with drift, may find use as an on-line monitor of interior trim materials.

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