Comparative of the adsorption performance of a multi-sorbent bed

Abstract

Ambient air is a very complex mixture of compounds, and has a very variable composition and concentration of pollutants. Hence, a good choice of sorbent or a good combination of different sorbents may allow the determination of a wide range of target compounds in air samples, as well as achieve high breakthrough volumes. The selective characteristics of the sorbent chosen would determine the removing of the target compounds from the air matrix. On the other hand, a choice of a proper sorbent for the range of the studied target compounds would eliminate problems derived from breakthrough values. The capacity of a sorbent to retain specific compounds is usually evaluated by measuring the breakthrough volume of a concrete compound on the sorbent. To maximize sampling efficiency, the maximum volume of air that can be sampled without loss of adsorbent must be known. Tenax TA has been determined to be a not suitable adsorbent for very volatile organic compounds (VVOCs, 0<boiling point<50-100ºC (WHO, 1989)). However, Tenax TA continues being one of the most widely used adsorbents for the preconcentration of VOCs. In addition to that, generally, a single adsorbent cannot be appropriate for the majority of compounds present in ambient air. Hence, a combination of several adsorbents may result in better performances. Two types of adsorbent tubes, one containing a mixture of three adsorbents (Carbotrap, Carbopack X, Carboxen 569) and another containing Tenax TA were compared to evaluate their usefulness as active adsorbents of ambient air VOCs, including VVOCs.

Peer Reviewed

Postprint (author’s final draft)