Pressurized Liquid Extraction (PLE)
Pressurized liquid extraction (PLE) is an extraction technique dedicated to solid matrices (also called pressurized hot solvent extraction –PSE, or accelerated solvent extraction - ASE).
It is based on a simple principle: a solid sample is extracted by a highly heated solvent (or mix of solvents) so as to accelerate the extraction process. As the solvent has to be maintained in its liquid state, the extraction is performed under pressure. It is conducted in several successive steps (see diagram).
Nitrogen purging recovers all the solvent and extracted compounds so that they can be transferred to the collection tube.
The solvent is pumped into the extraction cell, which is heated to the required extraction temperature (the cell pressure is adjusted according to the temperature).
The ground solid sample is put into the extraction cell (made of stainless steel to withstand high pressures).
After a given extraction time, the exit valve of the cell is opened: the liquid inside the cell is transferred to a collection tube.