A microconductometric ethanol sensor prepared through encapsulation of alcohol dehydrogenase in chitosan. Application to the determination of alcoholic content in headspace above beverages

A conductometric transducer is proposed for the first time for the detection of ethanol vapor. This ethanol microsensor is prepared by encapsulation of alcohol dehydrogenase (ADH) in chitosan. The electrodeposition of chitosan allows the addressing of the chitosan film on the microconductometric devices and to encapsulate ADH and nicotinamide adenine nucleotide (NAD⁺), which was monitored by IRTF. The analytical performance of the ethanol microsensor was determined in gaseous methanol, ethanol and acetone samples, collected from the head space above aqueous solutions of known concentration. The response time (t₉₀) of the sensor varies from 9 s to 46 s from lower concentrations to higher concentrations. The detection limit is 0.12v/v % in the gas phase, corresponding to 0.22 M in the liquid phase. The relative standard deviation for the same sensor is from 12% for lower concentrations to 2% for higher concentrations. ethanol sensor presents a 2.6 times lower sensitivity for methanol and 28.3 times lower sensitivity for acetone. A detection of ethanol in a red wine sample was performed.