A disposable reagentless screen-printed amperometric biosensor for the measurement of alcohol in beverages

A disposable sensor strip was fabricated by a screen-printing procedure. This consisted of a Meldola's blue modified carbon working electrode and a Ag/AgCl combined reference/counter electrode printed alongside each other on a PVC substrate. The working electrode was coated with a mixture containing alcohol dehydrogenase (10 units) and NAD(+) (60 mu g) to produce a sensor that would respond to alcohol. In order to improve the stability of the enzyme system the non-reducing sugar known as trehalose was incorporated into the enzyme/cofactor coating. Without trehalose the response to ethanol decreased dramatically over a period of 21 days, and no detectable signal was detected on the last day. With trehalose, 90% activity was observed 49 days after production. Using amperometry in stirred solution a calibration graph exhibited linearity up to a concentration of 35 x 10(-3) mol dm(-3) ethanol. The biosensor was used to determine the concentration of ethanol in a commercial gin sample and good agreement was obtained between the calculated value and that obtained by a recommended gas chromatographic procedure. Butan-1-ol > propan-1-ol > propan-2-ol also gave responses.