Alcohol Biosensor Based on the Immobilization of Meldola Blue and Alcohol Dehydrogenase into a Carbon Nanotube Paste Electrode

Abstract

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.

Keywords:

• Biosensor
• ethanol
• alcohol dehydrogenase
• Meldola Blue
• carbon nanotube paste electrode

The financial support of the Ministry of University and Scientific Research (MURST) is acknowledged.