Alcohol biosensor based on the immobilization of Meldola Blue and alcohol dehydrogenase into a carbon nanotube paste electrode

The preparation and electrochemical characterization of a new carbon nanotube paste (CNTP) amperometric biosensor for ethanol is described. The biosensor is formed by a CNTP electrode modified with the phenoxazine compound Meldola Blue (MB) as mediator. It shows a good electrocatalytic activity towards NADH oxidation at potentials around 0.0 V vs. Ag/AgCl, which represents a strong diminution in the overpotential. The biosensor is based on the activity of a commercially available alcohol dehydrogenase enzyme (ADH) and is realized by co‐immobilizing the enzyme ADH, the coenzyme NAD+, and the mediator into the paste. Analytical parameters such as enzyme, co‐enzyme and mediator immobilization concentration, pH, temperature, and probe lifetime are studied and optimized. The biosensor yields a linear response to 1×10−7 –4×10−6 mol/L ethanol at an operating potential of +50 mV (vs. Ag/AgCl), where interfering reactions do not occur, with a detection limit of 1×10−7 mol/L and a good reproducibility (RSD of 2.8%, n=6). Application of the biosensor to the determination of ethanol in alcoholic beverages was achieved successfully.