Strong evidence has been obtained which indicates that film diffusion controls the retention of non-polar organics of low aqueous solubility by the sorbent Tenax-GC. Model compounds which have been studied in this context include the four U.S. Environmental Protection Agency priority pollutants 0-dichlorobenzene, 1,2,4-trichlorobenzene, naphthalene, and hexachloro-1,3-butadiene. The data indicate that compounds such as these have large aqueous retention volumes on this sorbent. Once sorbed, little loss occurs for micrograms/l concentrations and sample volumes of several liters. Equations are developed which predict the percent recovery as a function of cartridge dimensions and sample volume flow rate. (Copyright (c) 1982 Elsevier Scientific Publishing Company).