Electrochemical sensor for NADH based on Meldola's Blue immobilized on silica gel modified with titanium phosphate

By means of cyclic voltammetry and amperometry, the evaluation of a modified electrode of Meldola's Blue immobilized on titanium phosphate coated onto a silica gel surface is described. The adsorbed Meldola's Blue was incorporated into a carbon paste electrode, and electrochemical behavior of the electron mediator was investigated under different conditions. The midpoint potential was found to be - 30 mV vs see and the ratio of cathodic and anodic peak current was about 1. Changing the pH of the solution between 3 and 8 did not shift the midpoint potential but for pH values lower than 3 the midpoint potential shifted to more positive potentials. The nature of the anion of the supporting electrolyte did not affect the response of the electrode, but the nature of the cation significantly influenced the voltammetric response when a sodium salt was used as electrolyte. The electrocatalytic oxidation of reduced nicotinamide adenine dinucleotide (NADH) was verified and the response time of the sensor was found to be 10 s by amperometry, applying 0 mV of potential vs see. The linear response range was 1.0 10(-5)-5.0 10(-5) M and the stability was very good with 500 measurements being carried out with the same electrode, obtaining a rsd lower than 4%. Copyright (C) 1996 Elsevier Science Ltd.4191465146