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Electrochemical Fuel Cell Breath Analysis |
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Electrochemical Fuel Cell Breath Analysis |
The second most widely accepted form of breath alcohol analysis today is the fuel cell. CMI’s sister company, Lion Laboratories, originally developed fuel cell technology in the 1970s. Fuel cell-based alcohol testers have been used primarily in preliminary, at-the-scene alcohol screeners by law enforcement for many years. More recently, testing instruments that utilize fuel cells have been approved for Department of Transportation-related evidential grade testing.
Alcohol Becomes an Electric Current
Fuel cells are true electrochemical devices and operate on the principle of oxidizing the substance to be analyzed. A catalytic surface is used to increase the oxidation process; this also comprises the anode of the cell. Alcohol is oxidized at the surface of one platinum electrode anode while atmospheric oxygen is simultaneously reduced at the second platinum electrode cathode—the counter electrode in the cell. The two electrodes are separated and supported by a thin, porous disk which is impregnated with an acidic electrolyte.
The fuel cell conditions favor the spontaneous electro-oxidation of alcohol at the cell anode. This process results in an electron flow to the cathode:
Since the volume of breath introduced into the fuel cell is constant, the electron flow is fully proportional to the amount of alcohol in the sample, and the electron flow generated, after passing through the instrument’s measuring electronics, is displayed in terms of the concentration of alcohol present in the breath sample.
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