Comparison of ppb-level gas measurements with a metal-oxide semiconductor gas sensor in two independent laboratories

• Published in: Sensors and actuators. B, Chemical Chemical, 2018-11, Vol.273, p.1037-1046
• Main Authors: Bastuck, M., Baur, T., Richter, M., Mull, B., Schütze, A., Sauerwald, T.
• Format: Article
• Language: English
• Subjects: Calibration transfer; Indoor air quality; Inter-lab comparison; Selective quantification; Volatile organic compounds
• ISSN: 0925-4005; 1873-3077; 1873-3077
• DOI: 10.1016/j.snb.2018.06.097

[Display omitted] •Formaldehyde and TVOC quantifiable below exposure limits.•Dynamic operation and signal processing eliminate effects of variable background.•Test data collected under different conditions at an independent lab.•Specific calibration requirements for chemical gas sensors pointed out. In this work, we use a gas sensor system consisting of a commercially available gas sensor in temperature cycled operation. It is trained with an extensive gas profile for detection and quantification of hazardous volatile organic compounds (VOC) in the ppb range independent of a varying background of other, less harmful VOCs and inorganic interfering gases like humidity or hydrogen. This training was then validated using a different gas mixture generation apparatus at an independent lab providing analytical methods as reference. While the varying background impedes selective detection of benzene and naphthalene at the low concentrations supplied, both formaldehyde and total VOC can well be quantified, after calibration transfer, by models trained with data from one system and evaluated with data from the other system. The lowest achievable root mean squared errors of prediction were 49 ppb for formaldehyde (in a concentration range of 20–200 ppb) and 150 μg/m³ (in a concentration range of 25–450 μg/m³) for total VOC. The latter uncertainty improves to 13 μg/m³ with a more confined model range of 220–320 μg/m³. The data from the second lab indicate an interfering gas which cannot be detected analytically but strongly influences the sensor signal. This demonstrates the need to take into account all sensor relevant gases, like, e.g., hydrogen and carbon monoxide, in analytical reference measurements.