Denuder sampling system for the determination of gaseous and particle-bound organic health hazardous substances

Determination of aromatic hydrocarbons in air using diffusion denuders

“…Denuders with a length of 90 cm, which have also been investigated, work up to flow rates of I 1/min without clearly decrease in uptake efficiency. The measured uptake rates were found to be in good agreement with theoretically predicted values calculated on the basis of the Gormley-Kennedy-equation [20,11].…”

“…The use of charcoal paper as wall coating material allowed to re-use the denuders after a thermal regeneration procedure. For details about the sampling system see [11].…”

“…The apparatus was laboratory-made. Regarding details about the operation principle of the test gas generators see earlier publications [11,[16][17][18][19]. For this study, the flows of the four gas generators were combined and mixed-up with the humidified gas stream.…”

“…For this purpose, a re-usable denuder sampling system was developed. The operation principle of the system as well as results of laboratory studies which demonstrate the satisfactory functioning of the denuders to trap chlorinated hydrocarbons and `polar' ketones have been published earlier [11]. The sampling system was primary intented to be used in the field of workplace air monitoring.…”

Amônia (NH3) atmosférica: fontes, transformação, sorvedouros e métodos de análise

“…Porém, em nosso laboratório, observou-se que quando a determinação é espectrofotométrica, deve-se evitar o uso do ácido ascórbico, pois ele resulta na formação de uma solução fortemente colorida, o que produz um branco muito alto, inviabilizando portanto a análise colorimétrica 52 . A maioria dos problemas relacionados com a caracterização do NH x em fases gasosa e particulada foram convenientemente solucionados através da introdução da técnica dos tubos de difusão [53][54][55] , conhecidos como "denuders", que permitem a amostragem prévia da fase gasosa e posterior coleta das partículas em "filter packs". A separação é baseada no princípio de que moléculas e partículas apresentam movimentos distintos dentro de um fluxo laminar.…”