Study of enzymatic electrodes using phenothiazine derivatives as mediators

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It is difficult to establish electrochemical sensors for aldehydes and alcohol, because those substrates are electro inactive and/or a large over voltage is necessary to oxidize. To circumvent these problems, this study attempted to construct the modified electrodes immobilized dehydrogenaces. When aldehydes and alcohol are oxidized enzymaticaly with dehydrogenaces, NADH was generated by reducing NAD^+. But the electro-oxidizing reaction of NADH is irreversible and difficult. I found that phenothiazine is a good mediator for oxidizing NADH previously. So I combined the enzyme electrodes above mentioned and phenothyazine to determine aldehydes and alcohol.After the solution of aldehyde dehydrogenace (ALDH) and NAD^+ was dropped no the membrane filter loaded phenothiazine and dried, the filter was fixed on glassy carbon electrodes. Acetaldehyde and five aldehydes could be determined by this modified electrodes. The similar results were obtained for alcohol. The determination of aldehydes was not affected by co-existence of ascorbic acid, because the potentials for oxidation of phenothiazine was low (200mV vs. SCE). Also meldora blue gave good results for the oxidation mediator of NADH.It was shown that the enzymatic electrodes were constructed by fixing the membrane filter loaded mediator, enzyme and cofactor. This modification procedure will contribute to the preparation of aldehydes and alcohol sensors.The paper about these results will be published.