Development of a monitoring tape for nitrogen dioxide in air

A porous cellulose tape containing a silica gel impregnated with a processing solution that includes p-toluenesulfonic acid, sulfanilic acid, N-(1-naphthyl)ethylenediamine dihydrochloride, glycerin and methanol has been developed to provide a highly sensitive means of detecting nitrogen dioxide in air. When the sample including nitrogen dioxide was passed through the tape, the color of tape changed to red. The degree of color change was proportional to the concentration of nitrogen dioxide at a constant sampling time of flow rate. The degree of color change could be recorded by measuring the intensity of reflecting light (555 nm). The detection limit was 1 ppb for nitrogen dioxide with a sampling time of 10 min and a flow rate of 30 ml/min. Reproducibility tests showed that the relative standard deviation of response (n = 10) was 3.5% for 0.1 ppm nitrogen dioxide. No interference was observed from methanol (0.5 vol.%), ammonia (40 ppm), ethylene (99.9 vol.%), hydrogen (99.9%), carbon monoxide (306 ppm), sulfur dioxide (50.6 ppm), carbon dioxide (20.5 vol.%), chlorine (2.5 ppm), hydrogen sulfide (27.1 ppm) or nitrogen monoxide (99.1 ppm).