Contaminant breakthrough: a theoretical study of charcoal sampling tubes.

A previously developed theoretical model was applied to investigate contaminant breakthrough on charcoal sampling tubes. Associated with the model are two important theoretical parameters. These parameters are k' (a rate constant) and tau (the time required for 50% contaminant breakthrough). In this study, values of K' and tau were determined for n-heptane at five different concentration levels in air: 98, 117, 234, 330, and 988 ppm. These values were used along with pertinent theoretical considerations to calculate the entire (0-100%) breakthrough curve (plot of percent breakthrough versus time) regarding the adsorbance of n-heptane on charcoal sampling tubes. In addition, available experimental data for perchloroethylene, isobutyl acetate, ethyl acetate, and dichloromethane were used in conjunction with the theory to generate theoretical breakthrough curves over the entire range of 0 to 100%. In each case, calculated theoretical breakthrough curves are in remarkable agreement with corresponding experimental data. With the use of an additional theoretical parameter, a, the theory was extended to calculate the weight of contaminant collected on a single element (section) of a charcoal sampling tube at 10% breakthrough and at each of several different contaminant assault concentrations.