The sorbent tube and the focusing trap may be packed with one or more sorbents. The type and number of sorbents depends on a number of factors including the sampling setup, the analyte volatility range, analyte concentration, and the humidity of the sample.
One of the most versatile and popular sorbents for thermal desorption is poly(2,6-diphenyl-p-phenylene oxide), known by its trademark Tenax.