ASSESSING BREAKTHROUGH TIMES FOR DENUDER SAMPLERS WITH EMPHASIS ON VOLATILE ORGANIC-COMPOUNDS

This paper presents a theoretical background useful for the prediction of cylindrical denuder sampler performance, applied to volatile organ ic compounds (VOC). Two methods are presented that can be used togethe r with any type of adsorption isotherm. One computer method is based o n a simple recursive modelling of the Gormley-Kennedy equation with a time-dependent denuder length. The other model uses an equation derive d directly from the Gormley-Kennedy expression. In practice, the latte r, simpler model can readily be used. The most crucial part in the bre akthrough assessment is associated with modelling the adsorption isoth erm. Two types of models have been considered: the Langmuir and the Fr eundlich adsorption isotherms. In order to facilitate the comparison b etween samplers with different adsorption capacities and different phy sical dimensions, a reduced length versus time plot is introduced.