Extraction methodologies in plants: general introduction
Résumé
The extraction stage is considered to be a key step of most analytical strategies, as it greatly influences the type and quality of analytical data. In case of plants, which are interesting materials for a broad range of domestic or industrial-scale applications, extraction is a particularly crucial step as solid samples are considered most of the time. Indeed, extractions from solids are well known to be more critical than from liquids, owing to limitations by diffusion and/or strong solute–solid interactions; solutes may also be trapped into cells within the plant materials. Consequently, careful knowledge about the plant material itself (its structure and composition) and whenever possible about the compounds to be extracted (their expected levels, polarity, and stability) is of great help for conceiving and optimizing an extraction process; the fate of the extract is also important to consider, as the selectivity expected for the extraction differs between target and fingerprint approaches. Practically, even though several extraction techniques are available, none is the best and should be recommended for any application. However, the use of recent techniques should be favored, as they reduce both the solvent volume and the time required for the extraction; the hyphenation or combination of techniques should be investigated to take benefit from the advantages of several techniques.