Thermal desorption backflush

Figure 1.2 Schematic of a thermal desorption process with tube desorption and normal/backflush trap desorption steps.

An alternative to desorption of the analytes trapped on an SPE carPidge with an organic solvent is thermal desorption (SPETD). In the first on-line SPETD setup, 100 to 500 pi of aqueous sample were injected into the packed liner of a PTV [75]. The water was evaporated at a high gas flow rate and a backflush setup inserted between the PTV and the analytical GC column ensured that no water entered the analytical column. Next, the analytes were desorbed and transferred to the analytical column by rapidly increasing the injector temperature. Tenax GR and TA were found to be suitable sorbents [76], that is, they combined sufficient retention power for analytes in the liquid phase (sorption), poor interaction with water (drying), and good thermal stability (desorption). The potential of the method was demonstrated by the analysis of 10 pg/L solutions of /7-alkanes and... 

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