A system to thermally desorb a sample into a multi-column GC or GCMS system that can use both the desorption system and GC system for optimizing injection rates, matrix management (e.g., water elimination), optimizing recovery of a specific range of chemicals, and system cleanup is described. Reversing the flow through a first column inside the GC can facilitate the elimination of excess, condensed water as well as heavy chemicals that could otherwise affect the operation and background of the GC. The elimination of flow through both the thermal desorber and a first column in the GC during sample preheat can accommodate the pre-expansion of the sample that could otherwise result in pre-release to the active carrier gas flow in other systems. Transfer lines and rotary valves can be avoided, improving system performance and longevity, with simple maintenance achieved by replacing a desorption liner and the first GC column.
