In HPLC the analytes which is tobe separated are separated into liquid solvent and for extraction of that various techniques are available like liquid-liquid extraction, solid-liquid extraction, solvent extraction, microwave, accelearted solvent extraction etc. whereas in GC the anaytes are heated at approx. 240 C and converted in to vapour which is passed through the separating column and extraction techniques is same in both processes.
Mechanism: HPLC- when solvent containing the analytes is passed through the separating column, due to their affinity with the stationary phase present in column (most commonly used C-18) it got attached with that due to interaction forces and separate.
GC- The sample is heated at higher temperature and converted into vapour and passed through the column which is separated.
analytes carrying medium