R. Appelqvist, G. Marko‐Varga, L. Gorton
1985
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0
Influential Citations
243
Citations
Quality indicators
Journal
Analytica Chimica Acta
Abstract
Abstract A chemically modified electrode for detection of dihydronicotinamide adenine dinucleotide (NADH) and dihydronicotinamide adenine dinucleotide phosphate (NADPH) is described. Graphite rods were modified by dipping them into solutions of-dimethylamino-1,2-benzophenoxzinium salt (Meldola blue). The modified electrodes were mounted in a flow-through cell in a flow-injection manifold. Samples (50 μl) of pure nicotinamide coenzymes produced strictly linear calibration graphs from 1 μM to 10 mM with a repeatability of 0.2–0.6% RSD. A packed-bed enzyme reactor (210 μl) containing immobilized glucose dehydrogenase was inserted in the manifold for glucose determinations. Oxidized coenzyme was also added to the carrier electrolyte. Straight calibration graphs were again obtained up to 1mM β- d -glucose. The detection limit was 0.25 μM β- d -glucose for 50-μl samples. The electrode was kept at −50 to 0 m V vs. SCE which was low enough to avoid interferences from ascorbic acid, uric acid or quinones.