Headspace vs. thermal desporption

[javaslinger]

Can someone please give me a better idea of the difference between purge and trap, dynamic headspace, and thermal desorption. The more I look, the more I see people describing them differently. I can't figure out the clear differenence or distinction.

Thanks,

Ken

[Earl]

Purge and trap is very similar to thermal desorption, essentially they are the same thing. With purge and trap you purge the analytes, using an inert gas, from their matrix onto a thermal desorption trap which is then heated onto a GC. With thermal desorption, you take the trap out and take samples directly onto the trap and then desorb them into a second trap within your system, which is arranged much like the purge and trap. Dynamic headspace, on the otherhand, does not use a trap (generally speaking), samples are heated in a closed vial and the volatalized gases are forced onto a GC.
Purge and trap for water matrices, thermal desorption for air and dynamic headspace for solids (generally speaking again).
Hope this helps!