Electrochemical sensors cross sensitivity

Experimental studies have also shown that selective detection is an important advantage of an electrochemical sensor, but sometimes their responses are affected by the presence of other gases (Park et al. 2003). As established in numerous experiments, cross-sensitivity is often observed when lype II or Type III potentiometric sensors are exposed to gas species that form thermodynamically more stable compounds or kinetically more favorable compounds in spite of lower thermodynamic stability (Weppner 1992). 

Fig. 6.14 Cross-sensitivity to oxygen of NO electrochemical gas sensors fabricated by lonotec Ltd. (68 ppm NO, rper=350 °C) (Reprinted with permission from http //www.ionotec.com/pdfs/noxsensor.pdf)...

Velasco G, SchneU JP, Croset M (1982) Thin solid-state electrochemical gas sensors. Sens Actuators 2 371-384 Wakagi A, Kuwano J (1994) Amperometric PbSnF -based oxygen sensors rapid response at room temperature in the operating pressure range 10 kPa-7.2 MPa. J Mater Chem 4(6) 973-975 Wang L, Kumar RV (2004) Cross-sensitivity effects on a new carbon dioxide gas sensor based on solid bielectrolsrte. Meas Sd Technol 15 1005-1010... 

Further sensor response modelling approaches are in development for other multi-gas sensor pairs. In summary, it is emphasized that accurate determination of plume gas ratios from co-deployed in situ electrochemical (and other) sensors requires a consideration of sensor response times. Non-identical sensor response times can result in scatter and bias in the derived gas ratios, particularly in cases where cross-sensitivities need to be removed. Reported plume gas ratios from multigas instruments may need to be revisited in this context, and the effect is likely also important in the monitoring of other environments, such as urban pollution. 

Fig. 15.6 Upper. SO2 mixing ratio time series obtained in a dilute downwind volcanic plume using low-noise electronics, logging output from two nrai-identical miniature electrochemical SO2 sensors with high sensitivity (black) and lower sensitivity (purple), at 1 Hz and 0.1 Hz, respectively. Lower. Mixing ratio abundances of excess (plume peaks - background) CO and NO2 at a cross-roads in an urban environment (Orleans, France), measured at 1 Hz using low-noise electronics, with the high-sensitivity SO2 sensm used to detect NO2 (cross-sensitivity —120 %) alongside a high-sensitivity sensor for CO...

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