In this work, a novel voltammetric ethanol biosensor was constructed using alcohol dehydrogenase (ADH). Firstly, alcohol dehydrogenase was immobilized on the surface of a glassy carbon electrode modified by cellulose acetate (CA) bonded to toluidine blue O (TBO). Secondly, the surface was covered by a glutaraldehyde/bovine serum albumin (BSA) cross-linking procedure to provide a new voltammetric sensor for the ethanol determination. In order to fabricate the biosensor, a new electrode matrix containing insoluble Toluidine Blue O (TBO) was obtained from the process, and enzyme/coenzyme was combined on the biosensor surface. The influence of various experimental conditions was examined for the characterization of the optimum analytical performance. The developed biosensor exhibited sensitive and selective determination of ethanol and showed a linear response between 1 × 10−5 M and 4 × 10−4 M ethanol. A detection limit calculated as three times the signal-to-noise ratio was 5.0 × 10−6 M. At the end of the 20th day, the biosensor still retained 50% of its initial activity.
A selective dopamine determination using a nafion-coated clinoptilolite-modified carbon paste electrode in the presence of ascorbic acid was studied. Both cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV) were used for measurements of dopamine. To improve the selectivity of the clinoptilolite-modified carbon paste electrode in presence of a high concentration of ascorbic acid, the electrode surface was coated with nafion membrane. Experimental parameters affecting the determination of dopamine, including the clinoptilolite ratio, nafion membrane thickness, preconcentration time, preconcentration solution pH, stripping solution pH and interferences are discussed. The developed sensor has a wide linear range, a low detection limit, and good stability and reproducibility. The sensor offers a good alternative to existing analytical methods for dopamine, permits a relatively short analysis time, and is simple, selective and inexpensive.
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