Ethanol and Lactic Acid Sensors Using Electrodes Coated with Dehydrogenase—Collagen Membranes

Abstract

Electrochemical and enzymatic reactions were studied for the purpose of making sensors of ethanol and lactic acid. The dehydrogenase–collagen membrane coated onto a platinum plate was prepared by the electroshaping method. The substrates were dehydrogenated and nicotinamide adenine dinucleotide (NAD) was reduced to form the reduced NAD (NADH) by an enzymatic reaction on the collagen membrane. Flavin mononucleotide (FMN) was chosen as an electroactive substance which could oxidize NADH to return NAD. The reduced FMN (FMNH2) was easily oxidized at the anode and a current was obtained. From the above reactions, the concentrations of ethanol and lactic acid in solutions were found to be determined by a current-substrate concentration relation. The accuracy was estimated to be within 10% error. The activity and stability of enzymes immobilized in the collagen membrane were investigated.