SNO2-BASED GAS SENSORS AS CHROMATOGRAPHIC DETECTORS

Being unselective, SnO2-based gas sensors can be used by means of appropriate methods. Various techniques, e.g., pattern recognition or time modulation of the sensor temperature are used. The lack of selectivity is compensated also when one uses these sensors in chromatographic systems. The chromatographic column itself separates the gas mixture into a time sequence, so the sensor receives the different gases at different moments; the first report was made by Figaro Engineering. We used SnO2-based gas sensors as chromatographic detectors; in this paper a complete description of our chromatographic system and of the chromatograms is given. The gas samples we analysed were CO/air mixtures in the 1 to 100 ppm range. The reproducibility was very good; the CO concentration was measured with a maximum error of 10% during a working day. The detection limit was below 1 ppm which is a very good result.