HUMIDITY-INDEPENDENT SOLID-STATE AMPEROMETRIC SENSOR FOR CARBON-MONOXIDE BASED ON AN ELECTROLYTE PREPARED BY SOL-GEL CHEMISTRY

An amperometric sensor consisting of a film of silica gel over an inte rdigitated microsensor electrode provided a humidity-independent respo nse to CO over the range of 9%-76% humidity. The residual solvent cont ents were in the 20%-50% range, depending on the age of the gels and t he humidity. Variations in this range did not change the sensitivity. Gaseous CO was quantified in the absence of a contacting liquid phase using either linear scan voltammetry (LSV) or now injection amperometr y (FIamp) at constant applied potential, With LSV after a 2-min exposu re to the sample, sensors with gels aged for 28-40 days yielded sensit ivities of 0.38, 0.41, and 0.38 nA/ ppmv for measurements at 9%, 33%, and 76% humidity, respectively; the corresponding correlation coeffici ents were 0.992, 0.995, and 0.999. The detection limit with FIamp was 5 ppmv.