ENZYMATIC METHOD FOR THE DETERMINATION OF FORMALDEHYDE

This paper describes a sensitive method for the determination of formaldehyde using two sequential reactions catalyzed by two enzymes, formaldehyde dehydrogenase and diaphorase. The principle of this method is based on the quantitative oxidation of formaldehyde, in the presence of formaldehyde dehydrogenase and oxidized nicotinamide adenine dinucleotide (NAD+), to produce formic acid and the reduced dinucleotide (NADH). The NADH produced then reacts with oxidized 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyltetrazolium (INT), in the presence of diaphorase, to produce formazan, a highly chromogenic compound. The formazan formed is measured spectrophotometrically at 500 nm and will be directly proportional to the amount of formaldehyde in the assay solution. As low as 0.05 μg/mL (1.6 × 10−6 M) formaldehyde concentration can be determined, and the linear range was up to 3 μg/mL (1.0 × 10−4 M). This enzymatic method is simple, sensitive, selective and can be used for the determination of formaldehyde in air, particularly in indoor environments. © 1990, American Chemical Society. All rights reserved.