Use of Enzymes for the Determination of Environmental Pollutants

Abstract

This paper describes three enzyme-based analytical methods for sulfur dioxide, formaldehyde, and formic acid using sulfite oxidase, formaldehyde dehydrogenase, and formate dehydrogenase, respectively. In the determination of sulfur dioxide, air samples are collected in triethanolamine buffer solution and then reacted with sulfite oxidase/NADH/NADH peroxidase solution. The decrease in NADH, which is proportional to the concentration of sulfur dioxide, is determined spectrophotometrically at 340 nm or fluorometrically at λ_ex of 340 nm and λ_em of 467 nm. In the determination of formaldehyde, formaldehyde dehydrogenase catalyzed the reaction of formaldehyde with NAD⁺ to form NADH which can be measured spectrophotometrically. For higher sensitivity and better detection limit, NADH is coupled to INT/diaphorase to produce formazan, a highly chromogenic compound. In the determination of formic acid, formate dehydrogenase is employed and NADH formed is measured spectrophotometrically. The NADH produced is also coupled to the diaphorase-catalyzed reduction of resazurin to form resorufin which can be measured fluorometrically.