Laboratory retention of vapor-phase PAHs using XAD adsorbents

This investigation focuses on the retention of polycyclic aromatic hydrocarbons (PAHs) on XAD (-2, -4, and -16) resins, which is crucial for estimating PAH gas/particle partition coefficients. The XAD resins were found to exhibit higher specific retention volumes (Vg, net gas-phase retention volume per unit weight (gram) of sorbent) than PUF for some 3-ring PAHs at 20 oC. The 3-ring compounds broke through the XAD adsorbents more easily than the 4-ring compounds at constant temperature. For the equation, Log Vg=m log PL+b (PL: subcooled liquid vapor pressure) the average m values were approximately –0.2 and –0.3 at 20 and 40 oC, respectively. Moreover, the Vg values were lower at 40 oC than at 20 oC for each PAH compound. The XAD-4 appeared to have a greater Vg value (adsorbent weight based) for each compound among the adsorbents at 40 oC. It was possible that PAH micropore adsorption dominated on XAD-4, different from the predominance of the PAH surface adsorption on the other two adsorbents.