Development of a Monitoring Tape for Formaldehyde Using Hydroxylamine Sulfate and Methyl Yellow

Abstract

A porous cellulose tape impregnated with a coloring solution that includes hydroxylamine sulfate, Methyl Yellow (pH indicator; pH 2.9-4,0, red—yellow), glycerin and methanol has been developed to provide a highly sensitive means of detecting formaldehyde gas. Formaldehyde reacts with hydroxylamine sulfate to produce sulfuric acid. When a sample including formaldehyde was passed through the tape, the color of the tape changed from yellow to red. The degree of color change was proportional to the concentration of formaldehyde at a constant sampling time and flow rate. The degree of color change could be recorded by measuring the intensity of reflecting light (555 nm). No interference was observed from carbon monoxide (100 ppm), nitrogen monoxide (50 ppm), nitrogen dioxide (105 ppm), carbon dioxide (4,9%), hydrogen (100%), hydrogen sulfide (32 ppm), or hydrogen fluoride (6 ppm). The response of acetaldehyde and propionaldehyde were one fortieth and three-hundredths of that of formaldehyde, respectively, Reproducibility tests showed that the relative standard deviation of relative intensity (n=10) was 3.4% for 4 ppm formaldehyde. The detection limit was 0.1 ppm for formaldehyde at a sampling time of 5 min and a flow rate of 400 ml/min.