Biochemical gas-sensor (bio-sniffer) for breath analysis after drinking

An alcohol oxidase (AOD) immobilized gas-sensor (bio-sniffer) with stick-type configuration was developed for convenient analysis of ethanol vapor. The stick-type sniffer device was constructed in a sandwich configuration with a filter paper placed between carbon- and Ag/AgCl electrodes. The electrode-coated paper was shaped by knife into 2 mm-wide stick. In order to isolate a sensitive- (length: 5 mm) and terminal-areas, an epoxy-resin adhesive was applied to the middle part of the narrow stick paper. AOD was immobilized to the sensitive area with photocrosslinkable polymer. The characteristics of the stick-type sniffer moistened with phosphate buffer were assessed using standard ethanol vapor supplied from a gas generator. The oxidation current of hydrogen peroxide, produced by the AOD enzymatic reaction by applying ethanol vapor, was detected a computer-controlled potentiostat at a fixed voltage of +900 mV. The calibration range of the ethanol sniffer covered the concentration range encountered in breath after alcohol consumption including the permissible legal limit (130 ppm) for driving, and the sensing range of smell in humans. As the physiological application, the bio-sniffer was used to monitor the concentration change of breath ethanol after drinking.