Galactose electrochemical oxidation

The presence of glucose, fructose, galactose, arabinose and citric, malic and tartaric acid did not produce interference on the quantification of gluconic acid. Only ascorbic acid yielded an amperometric response under the working conditions, due to the electrochemical oxidation of this compound at the applied potential. Nevertheless, the content of gluconic acid in honey samples is remarkably higher than the possible content of ascorbic acid. Consequently, no significant interference should be expected in the analysis of the proposed real samples. 

Other examples of amperometric enzyme electrodes based on the measurement of oxygen or hydrogen peroxide include electrodes for the measurement of galactose in blood (galactose oxidase,enzyme), oxalate in urine (oxalate oxidase), and cholesterol in blood serum (cholesterol oxidase). Ethanol is determined by reacting with a cofactor, nicotinamide adenine dinucleotide (NAD" ) in the presence of the enzyme alcohol dehydrogenase to produce the reduced form of NAD", NADH, which is electrochemically oxidized. Lactate in blood is similarly determined (lactate dehydrogenase enzyme). 

In 1998, a third efficient functional model of galactose oxidase was published by Saint-Aman et aL 86) who performed the electrochemical catalytic oxidation of primary alcohols to the corresponding aldehydes. was obtained from one equivalent Cu C104, 2 equivalents of triethylamine, and one equivalent of the ligand N,N-his (2-hydroxy-3,5-di- cr -butylbenzyl)-... 

This paper will discuss the characteristics of this detector with respect to the above applications. Stable oxides are formed at potentials in excess of 200 mV vs. SUE. A chrono-coulorometric experiment has been used to follow the formation of the oxide layer, loss of silver due to the formation of soluble hydroxy species, and reduction of the oxide to metallic silver. With respect to carbohydrate oxidation, several factors are important including hydroxide concentration, temperature and potential. The long term stability has been considered and is analyte dependent. Many carbohydrates (i.e. glucose, fructose, galactose) do not cause any observable dimunition while some analytes (cytidine, glycerol) cause a noticable loss of sensitivity. In all cases the sensitivity can be restored by electrochemical treatment in which the oxide is reduced and regenerated. 

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