Amperometric determination of formaldehyde via the hexacyanoferrate(III) -coupled dehydrogenase reaction

An enzymatic method with amperometric detection was developed for the determination of formaldehyde. Formaldehyde is first oxidized by reaction with NAD⁺ in the presence of formaldehyde dehydrogenase. The resulting NADH is then oxidized by hexacyanoferrate(III) in the presence of diaphorase to produce hexacyanoferrate(II). The anodic current generated by oxidation of the hexacyanoferrate(II) at the surface of a glassy carbon working electrode, held at a potential of 0.40 V vs. an Ag/AgCl reference electrode, is measured. The effects of solution conditions are examined and a linear relationship between rate of current change and formaldehyde concentration is obtained from 0.01 to 0.5 μg ml^?1 with a correlation coefficient of 0.9998. The relative standard deviation for the proposed method is 6.4% at 0.01 μg ml^?1 formaldehyde and 0.88% at 0.5 μg ml^?1.