Diffusion denuder technique

Diffusion Denuders for Specific Organic Compounds. Diffusion de-nuder techniques have been applied successfully to sampling individual organic materials, including pesticides (82), nicotine (83, 84), and PAH compounds (63). The methodology and results relating to PAH compounds are detailed here. 

Nitric acid and certain other gases can be sampled by diffusion denuder tubes, eliminating artifacts associated with filter collection. The annular denuder variation of this technique permits sampling at higher flow rates (5 to 10 L/min), hence may be useful for airborne sampling, although no airborne data have been reported to date. 

Mixtures of gases and particles can be separated by diffusion denuders combined with filter samplers. Chemically reactive gases are collected on the surface of selectively coated diffusion denuder tubes, whereas particulate components are collected on subsequently placed filters (Stevens et al. 1978 Klockow 1982). Until now, this method has been used exclusively for non-metallic components. Although it can be foreseen that denuder techniques may also be used for the separation of gaseous and particulate metallic components. 

P. Mikuska, K. Motyka, Z. Vecera, Determination of nitrous acid in air using wet effluent diffusion denuder-FIA technique, Talanta 77 (2008) 635 41. 

A diffusion separator has been described as an alternative to the denuder for eliminating filtration artifacts (Eisenreich and Hornbuckle, 1997 Turpin et al., 1993,1997, 1999). The separator, which uses neither filters nor a denuder section, relies on the different mobilities of gases and particles to separate them. The technique was used to speciate particulate and gaseous PAHs in Minneapolis air (Eisenreich and Flornbuckle, 1997). Comparison of filter-... 

Reflection electron microscopy (REM) is used to observe denuded zones created at the terrace edges. By analyzing the denuded zones as a funetion of temperature and time, the diffusivity may be calculated. This technique is limited to studying surfaees where islands may be easily distinguished, as on the Si(lOO) surface where the 2x1 and 1x2 reconstructions that alternate in successive layers are clearly visible [95Doil]. The resolution of the technique is on the order of 0.5 pm... 

For determination of Pb(C2H5)4 and other tetraalkyllead compounds in air by a diffusion technique employing an ICl-coated annular denuder, see [520] see also [442]. For determination of gaseous lead in exhaust gas by microwave-induced air-plasma emission spectrometry, see [532]. Methods for determination of Pb(C2H5)4 in hazardous waste incinerator flue gas were developed, based on gas chromatographic separation and detection by flame ionization or mass spectrometry [565]. 

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