Analytical Sciences

Abstract − Analytical Sciences, 22(5), 789 (2006).

Development of a Detection Tablet for a Portable NO2 Monitoring System
Gaku ISHIGURO,* Tetsuya KAWABE,* Nobuo NAKANO,* and Kunio NAGASHIMA**
*Riken Keiki Co., Ltd., 2-7-6, Azusawa, Itabashi, Tokyo 174-8744, Japan
**Faculty of Engineering, Kogakuin University, 2665-1, Nakanomachi, Hachioji, Tokyo 192-0015, Japan
We have already developed a HCHO monitoring system which is called FP-30. In this experiment, we have developed a NO2 detection tablet which can be used by the monitoring system. The detection tablet for the NO2 was constructed with the sensing paper: porous cellulose paper that contains silica gel as an adsorbent, N-1-naphthylethylenediamine dihydrochloride (NED), and glycerin. The NO2 in sample gas was blown over and adsorbed on the surface of the sensing paper. Then the NO2 reacted with NED, producing a yellow compound. The coloring reaction took place on the surface of the sensing paper. The degree of color change of paper from white to yellow was monitored as a function of the intensity of the reflected light (λ = 475 nm) of an LED. The detection limit was 0.01 ppm when the sampling time was 30 min, and the flow rate of sample gas was 250 ml/min. This sensing paper process was not interfered with by acetaldehyde, acetone, alcohols, hydrocarbons, carbon monoxide or carbon dioxide. The NO2 concentrations in the rooms of a house or school were monitored using this monitoring system and the standard chemiluminescence method. The concentrations of NO2 monitored by both methods were within 18% of the average. This highly sensitive, selective, and handy NO2 gas monitoring system will be widely applicable and convenient for users who are not specialists in this field.