Alcohol and Electrochemical Sensors
For any gas to be detectable by an electrochemical sensor, it must first be “electroactive.”
In voltammetry and related techniques, a substance that undergoes a change of oxidation state, or the breaking or formation of chemical bonds, in a charge-transfer step.
Most alcohols are electroactive. Indeed, considerable work has been done in the development of alcohol fuel cells, and several alcohol breath meters used by police agencies are based on electrochemical sensors.
Parts-per-million level concentrations of alcohol would simply be detected, and would react away, generally without incident. However, in many cases where our sensors are exposed to alcohol, the concentrations are not low. Rather, the concentrations are at levels in excess of 500 ppm, and even higher. Bear in mind that the OSHA PEL for isopropyl alcohol is 400 ppm.
At such relatively high concentrations, an Interscan sensor—intended for operation at ppm and sub-ppm levels—will surely react to the alcohol, but this overexposure will cause the instrument to go off-scale, until all the alcohol reacts away. Moreover, certain reaction products could build up on the sensing electrode, creating a long-term “background” effect, that can markedly affect sensor performance.