Reagentless enzyme-based sensor using a gas-permeable membrane for determination of alcohols

The sensor described consists of an anode mounted with immobilized alcohol dehydrogenase from Gluconobacter oxydons, a cathode and an electrolyte containing hexacyanoferrate(III). Its surface was covered with a gas-permeable membrane. Measurements were made without consumption of reagent by pumping a sample solution through the flow cell for 1 or 2 min. The calibration plot of the sensor using a porous PTFE gas-permeable membrane was linear up to 0.08 mM of ethanol with a relative standard deviation of 0.5%. The linear range was extended to 1.8 mM if a silicone rubber membrane was used. The selectivity was satisfactory; the penetration of interfering compounds was prevented by the gas-permeable membrane. Results obtained with the sensor and by gas chromatography agreed within 3.4% for alcohol beverages. The sensitivity decreased to 85% of its initial value after continuous use for 9 days. Responses of the sensor to 1-propanol and 1-butanol were examined.