The tin oxide electrochemical sensor is the active component in the personal breathalyzer used for ethanol detection. The sensor works by ethanol vapor reacting with oxygen species adsorbed to the SnO2 surface, then releasing trapped electrons back into the conduction band which changes the output voltage. However, to the best of our knowledge, the analytical characterization of this sensor for other volatile organic compounds has not been explored. This sensor, about 1.6 cm in diameter and length, with a hard-wired resistor, is commercially available for less than $10. Only a 5 volt power supply and a voltmeter for readout are required to complete the instrument. Headspace volatility was evaluated in 12 mL glass vials. Response time for detection of concentrated alcohol solutions to a consistent mV plateau value was about 120 sec. Application to following the proof during the distillation of ethanol or percent isopropanol in rubbing alcohol products appears feasible. Determination of ethanol in beer, wine, and rum has compared favorably to such analysis done by indirect HPLC. Amines such as tetramethylethylenediamine as well as other oxygenated organic compounds such as ketones, ethers, and esters are detected easily by this sensor at low percentages. However, the sensor appears to poorly discriminate against specific compounds in the sample matrix. Propylene glycol has been shown to significantly reduce sensor detection values, whereas orange oil has been shown to substantially increase readings.
Author: Luke A. Miller
Faculty Advisor: Neil D. Danielson, Department of Chemistry
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