Electrocatalytic Oxidation of NADH in Flow Analysis by Graphite Electrode Modified with 2,6-Dichlorophenolindophenol Salts
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Authors
A.B.Florou,
M.I.Prodromidis,
S.M.Tzouwara-Karayanni
M.I.Karayannis
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WILEY-VCH Verlag
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peer reviewed
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Electroanalysis
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The preparation of a 2,6-dichlorophenolindophenol (DCPI) modified graphite electrode is described. DCPI was successfully immobilized by physical adsorption onto a plain graphite electrode (DCPI-CME) and onto graphite electrodes pretreated with lanthanum nitrate (DCPI-La-CME) or thorium nitrate (DCPI-Th-CME). The electrochemical behavior of DCPI-CME was extensively studied using cyclic voltammetry. The electrochemical redox reaction of DCPI was found to be fairly reversible at low coverage with Eo' = +55 mV (vs. Ag/AgCl/3M KCl) at pH 6.5. A pKa value of 5.8 ± 0.1 for immobilized form of DCPI is determined from the intersection of the lines in the plot Eo' vs. pH. The current Ip has a linear relationship with the scan rate up to 1200 mV s�1, which is indicative for very fast electron transfer kinetics. The calculated value of the standard rate constant is ko = 18 ± 4 s�1. No decrease of either the anodic or the cathodic current of the cyclic voltammogram was observed after 500 runs of successive sweeps. The influence of the morphology of the electrode surface on the electrochemical behavior of the DCPI-CME was studied and a mathematical model is proposed, which partly describes the dependence of the geometrical area of the electrode surface on the grid of the emery paper. The modified electrodes were mounted in a flow-injection manifold, poised at +60 mV (vs. Ag/AgCl/3M KCl) and a catalytic current due to the oxidation of NADH was observed reducing thus the oxidation overpotential of NADH for about 400 mV. Interference from various reductive species present in real samples was investigated. The repeatability was 1.2 % RSD (n = 10 for 0.1 mM NADH). The sensor showed good operational and storage stability.
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Keywords
Electrocatalytic oxidation of NADH, DCPI chemically modified electrodes, Cyclic voltammetry, Flow injection analysis
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http://onlinelibrary.wiley.com/doi/10.1002/%28SICI%291521-4109%28199812%2910:18%3C1261::AID-ELAN1261%3E3.0.CO;2-M/abstract
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en
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Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας