mose of standard methods adopted as an offcial method are essentially composed of the active sampling method coupled with such detection methods as Saltzman method[3], chemi- luminescence method[4], sodium arsenite methodf51, and triethanolamine guaiacol/ sodium metabisulfite (TGS) method[6]. The measurement of NO; and/or NO3"in absorbing solutions can be done in short time, whereas a long interval time is required for absorbing and concentrating NO;, in the absorbing solutions. Further, apparatuses used are expensive, big, and heavy; therefore, such apparatuses cannot be used outdoor. When it is necessary to measure the environmental concentration of NO2 in a wide area, the passive sampling method is used. In the method described above, NO, is usually collected by diffusion on absorbent-impregnated screens in badges or
capsules. The apparatuses in passive sampling methods are simple, small and less expensive. Several kinds of the passive sampling methods have been used so far: a nitration plate with firebrick[?], a soaked glass bead@], and a silica gel[91flOI soaked in a triethanolamine (TEA) solution, an alkali filter paper[llJ, and a TEA filter paper method[12][131. Recently, the methods with Teflon membrane filter[14], capillary[15] and kieselguhr