COMPUTER-PROGRAM FOR SIMULATING THE PERFORMANCE OF THICKBED DIFFUSIVE SAMPLERS - PREDICTED AND EXPERIMENTAL SAMPLE LOSS DUE TO REVERSIBLE ADSORPTION

Using experimentally determined adsorption isotherm constants, a computer model of the performance characteristics of thick-bed diffusive samplers was developed. The model has previously been used to calculate effective uptake rates, and it is now shown that it will predict the loss of sample due to reversible adsorption. The predicted losses of pentane, hexane, heptane and toluene from Tenax(R) TA and Chromosorb(R) 106 compare well with experimental data. The samplers were exposed for 2-16 h, followed by desorption for 2-21 h. The largest deviation between predicted and experimental values was found for pentane on Tenax TA, where the average experimental loss was 30% and the average predicted loss was 41%. Pentane on Chromosorb 106 showed an average experimental loss of 20% while the predicted loss was 19%. Possible applications are the measurements of strongly bound compounds in air, determined with high accuracy, while doing screening measurements of weaker bound compounds, with a less but estimated accuracy, on the same adsorbent.