Development of a glass ampoule system for evaluation of long-term sorption/desorption behavior of vapor phase volatile organic compounds in geosorbents

Knowledge of the sorption/desorption behavior of volatile organic compounds (VOCs) in natural materials is critical to understanding the fate and tran sport of contaminants in saturated and unsaturated soil and sediment system s. Currently, a number of protocols exist to evaluate sorption isotherms of VOCs in the vapor phase. However, each of these methods possesses an inabi lity to equilibrate samples for long periods of time while maintaining high mass recoveries; this problem is exacerbated when the compounds of interes t exhibit high vapor pressures. This paper describes a new headspace analys is technique which employs a new glass ampoule system, which, when compared with commercially available glass arnpoule systems and three other headspa ce analysis methods used for batch sorption experiments, was shown to exhib it improved mass recovery over long equilibration periods. The new headspac e analysis protocol was also evaluated for application to full cycles of so rption/desorption experiments with similarly good mass recoveries. Results of this study show that the new headspace analysis protocol employing the n ew glass ampoule system is a reliable and relatively inexpensive method for obtaining both sorption and desorption data for VOCs.