Improvement of a monitoring tape for nitrogen dioxide in air

A porous cellulose tape containing a silica gel that was previously impregnated with a processing solution containing p-toluenesulfonic acid, sulfanilic acid, N-1-naphthyl ethylene diamine dihydrochloride, ethylene glycol and methanol has been developed to provide a highly sensitive detection of nitrogen dioxide in air. When the sample including nitrogen dioxide was passed through the tape, the color of tape changed to red, and the degree of color change could be recorded by measuring the intensity of reflecting light (555 nm). The calibration graph was linear up to approximately 0.10 ppm. The detection limit was 0.5 ppb for nitrogen dioxide with a sampling time of 8 min and a flow rate of 60 ml min(-1). No interferences were observed from ammonia (40 ppm), sulfur dioxide (51 ppm), carbon dioxide (21%), ozone (0.75 ppm), hydrogen sulfide (27 ppm) or nitrogen monoxide (99 ppm).