The extraction process
Regardless of the conditions and the technique used, the profile of the extracted quantity is always the same according to the progress of extraction (see graph):
- At first, the compound to be extracted is solubilized by the extractant – the extracted quantity increases quickly with the extraction duration
- Then a plateau is observed – the extraction process is controlled by diffusion (and sometimes by desorption in the case of certain solid matrices).
Reaching the plateau does not necessarily mean that the compound has been entirely extracted. On the other hand, it is important to understand the shape of the curve for an intended application and to choose an appropriate extraction duration.