*2.3.1.2.1 Supercritical fluid extraction*

It is a process of separating one component (the extractant) from another (the matrix) using supercritical fluids as the extracting solvent. In practice, more than 90% of all analytical supercritical fluid extraction (SFE) is performed with carbon dioxide (CO2) as the most used fluid. The CO2 is chosen for several reasons including the following: relatively low critical pressure (74 bars) and temperature (32°C), inertness, non-toxic, nonflammable, high soluble, non-corrosive, safe, available in high purity at relatively low cost, perfect conditions for thermosensitive compounds extraction, selectivity for desired compounds, and easy removal from the extract. At lower temperatures, to avoid potential damage of desired components of EOs, supercritical CO2 extraction technique is highly recommended [39, 40]. Extraction of EOs by SFs, particularly with CO2, provides products free of toxic waste, having a higher quality (especially it reserves the thermal instability of compounds) than EOs obtained by conventional methods (**Figure 6**) [40–42].
