Extraction (extraction) is the extraction of substances from various materials with solvents (extractants) in special devices called extractors. Extraction is used to extract medicinal substances from raw materials of plant and animal origin, as well as in chemical-toxicological and biochemical analyzes.
Extraction (extraction; from the Latin. Extrahere - pull out, extract) - the process of extracting a substance with a solvent from solutions or solid (vegetable, animal, mineral) materials. Extraction is associated with diffusion, dissolution, and for biological objects - with dialysis. Extraction from liquids is based on the distribution law, according to which
where: m 0 - the amount of extracted substances contained in the volume of the solvent V A before extraction; m n - the amount of this substance remaining in the same volume after the n-fold extraction; V B - the volume of solvent (extractant), which is extracted each time; K - distribution coefficient of the extracted substance between two solvents. The extractant must not mix with the solvent, dissolve the extractable well and poorly dissolve the associated substances, have a low viscosity and diffuse well. It is desirable that the extractant prevents the development of microflora and is not harmful to the body. The most common extractants are: water, alcohol, ether, glycerin, oils, chloroform, etc. Sometimes extraction is carried out with several solvents sequentially or in a mixture.
For quick and complete extraction, increase the contact surface of the phases, grinding and mixing the material; create a possible greater concentration difference, increasing the amount of extractant, often changing it or using the principle of counterflow, increase the temperature, increase the time of extraction, add electrolytes. Extraction of the substance to the data: the volume of the extractant will be more complete if this volume is divided into a number of portions and the extraction is performed repeatedly, rather than once by the whole volume of the extractant. Extraction is usually carried out in a separatory funnel or in an extraction apparatus.
In fig. 1 shows the Soxhlet apparatus for the extraction of solids (1 - refrigerator; 2 - cylindrical part of the device; 3 - siphon; 4 - flask for solvent).
In fig. 2 — an apparatus for automatic extraction of a liquid (1 — a refrigerator; 2 — a separating funnel; 3 and 6 — heaters; 4 — an extraction chamber; 5 — a siphon; 7 — a flask for collecting the extract).
Extraction is performed by shaking the extractant with a solution or solid material (periodic extraction) or by constantly passing the extractant through them (continuous extraction). The solution containing the extracted substance (extract) is separated from the residue by filtration, centrifugation or decanting after settling (decantation). Extraction is widely used in biology, medicine, pharmacy, industry for the isolation and separation of proteins, fats, vitamins, hormones, antibiotics, isotopes, and the production of synthetic rubber, caprolactam, for wastewater treatment, in the manufacture of herbal medicines, tinctures, etc. Food (meat, berry, malt), tanning, dyeing, medicinal and other extracts are widely used.