Supercritical fluid extraction as a means of cleaning and desorbing common air sampling sorbents

Supercritical fluid extraction (SFE) with carbon dioxide has become an increasingly popular alternative extraction method to Soxhlet extraction for the measurement of organic compounds adsorbed on solid matrices. The application of SPE to air sampling materials for recovery of adsorbed (collected) organic pollutants is an obvious extension of this technology. To develop appropriate methods, the first practical steps are the determination of the physical and chemical stability as well as the general cleanliness of the candidate adsorbent materials under the demanding SFE conditions and compare such results to parallel tests with Soxhlet extraction. This paper describes exploratory research with the common air sampling media Tenax-GC, Tenax-GR, XAD-2, and Carboxen 563. All were found to be physically and chemically compatible with SFE. XAD-2 and Carboxen 563 have an initial cleanup advantage over the two Tenax types and Tenax-GC is subject to artifact formation form ozone exposure. All four sorbent types could, once cleaned, be stored for four weeks in sealed cartridges without buildup of contaminants indicating that the SFE cleanup procedure removes impurities from within the sorbents.