QUANTITATIVE DETECTION OF GASEOUS SUBSTANCES AT LOW ppm AND SUB-ppm LEVELS BY MEANS OF ENZYME DIFFUSION BADGES

Abstract

A family of diffusion dependent enzyme badges for measurement of gaseous hydrogen peroxide, formaldehyde, acetaldehyde, and ethanol is presented. The main functional part of it is a porous solid support at the top of which the required enzymes are applied, e.g. by lyophilization. The badge is activated by dipping the enzyme-coated support into a reagent solution. Capillary forces and evaporation produce a flow of reagent solution to the surface resulting in a permanent water and reagent supply as well as in concentrating the enzyme(s) at the surface. The gaseous substrate molecules reach the surface by diffusion. The high specifity of the badges results from the catalytic conversion of the gaseous compounds by the enzymes. The colored compounds finally produced by the combined enzymatic and chemical reactions are concentrated at the surface because evaporation prevents their diffusion into the support material.?) This way a selective determination of the concentration of gaseous enzyme substrates becomes feasible, simply by color comparison or by reflectometry. These badges allow simple, selective and reliable spot measurements of hydrogen peroxide and formaldehyde down to 100 ppb after 15 min exposure.