THERMAL-DESORPTION EFFICIENCIES FOR DIFFERENT ADSORBATE ADSORBENT SYSTEMS TYPICALLY USED IN AIR MONITORING PROGRAMS

Thermal desorption efficiencies at different temperatures have been determined for selected C5 - C-10 hydrocarbons (isoprene, benzene, toluene, p-xylene, o-xylene, mesitylene, 1,2,4-trimethylbenzene, 1,2,3-trimethylbenzene, alpha-pinene, and beta-pinene) on four adsorbents (Tenax-TA, Tenax-GR, Carbotrap, and Chromosorb 106) using a very simple vapour phase spiking/double desorption method. This two-stage desorption method does not require an accurate amount of analyte to be added to the adsorbent. It is found that alpha- and beta-pinene can be partly or completely decomposed on some adsorbents. A method for estimating the thermal desorption conditions giving complete desorption from data on retention volumes at different temperatures for the adsorbate/adsorbent system is also discussed.