Extraction in chemistry is a

separation process A separation process is a method that converts a mixture or a solution of chemical substances into two or more distinct product mixtures, a scientific process of separating two or more substance in order to obtain purity. At least one product mi ...

consisting of the separation of a substance from a

matrix Matrix most commonly refers to: * ''The Matrix'' (franchise), an American media franchise ** ''The Matrix'', a 1999 science-fiction action film ** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchis ...

. Common examples include '' liquid-liquid extraction'', and ''

solid phase extraction Solid-phase extraction (SPE) is an extractive technique by which compounds that are dissolved or suspended in a liquid mixture are separated from other compounds in the mixture according to their physical and chemical properties. Analytical labor ...

''. The distribution of a solute between two phases is an equilibrium condition described by partition theory. This is based on exactly how the analyte moves from the initial solvent into the extracting solvent. The term ''washing'' may also be used to refer to an extraction in which impurities are extracted from the solvent containing the desired

compound Compound may refer to: Architecture and built environments * Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall ** Compound (fortification), a version of the above fortified with defensive struct ...

Types of extraction

Liquid–liquid extraction Liquid–liquid extraction (LLE), also known as solvent extraction and partitioning, is a method to separate compounds or metal complexes, based on their relative solubilities in two different immiscible liquids, usually water (polar) and an orga ...

Solid-phase extraction Solid-phase extraction (SPE) is an extractive technique by which compounds that are dissolved or suspended in a liquid mixture are separated from other compounds in the mixture according to their physical and chemical properties. Analytical labor ...

* Acid-base extraction * Supercritical fluid extraction * Ultrasound-assisted extraction * Heat reflux extraction * Mechanochemical-assisted extraction * Maceration * Microwave-assisted extraction * Instant controlled pressure drop extraction (DIC, from the French, Détente instantanée contrôlée) *

Perstraction Perstraction is a membrane extraction process, where two liquid phases are contacted across a membrane. The desired species in the feed, selectively crosses the membrane into the extracting solution. Perstraction was originally developed to overc ...

Laboratory applications and examples

Liquid-liquid extractions in the laboratory usually make use of a

separatory funnel A separatory funnel, also known as a separation funnel, separating funnel, or colloquially sep funnel, is a piece of laboratory glassware used in liquid-liquid extractions to separate (''partition'') the components of a mixture into two immiscib ...

, where two immiscible phases are combined to separate a

solute In chemistry, a solution is a special type of homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. If the attractive forces between the solvent ...

from one phase into the other, according to the relative solubility in each of the phases. Typically, this will be to extract organic compounds out of an aqueous phase and into an organic phase, but may also include extracting water-soluble impurities from an organic phase into an aqueous phase. Common extractants may be arranged in increasing order of polarity according to the

Hildebrand solubility parameter The Hildebrand solubility parameter (δ) provides a numerical estimate of the degree of interaction between materials and can be a good indication of solubility, particularly for nonpolar materials such as many polymers. Materials with similar valu ...

ethyl acetate Ethyl acetate ( systematically ethyl ethanoate, commonly abbreviated EtOAc, ETAC or EA) is the organic compound with the formula , simplified to . This colorless liquid has a characteristic sweet smell (similar to pear drops) and is used in glues ...

acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscib ...

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

< acetone:water (7:3) < ethanol:water (8:2) < methanol:water (8:2) <

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

Solid-liquid extractions at laboratory scales can use

Soxhlet extractor A Soxhlet extractor is a piece of laboratory apparatus invented in 1879 by Franz von Soxhlet. It was originally designed for the extraction of a lipid from a solid material. Typically, Soxhlet extraction is used when the desired compound has a ' ...

s. A solid sample containing the desired compound along with impurities is placed in the thimble. An extracting solvent is chosen in which the impurities are insoluble and the desired compound has at least limited solubility. The solvent is refluxed and condensed solvent falls into the thimble and dissolves the desired compound which then passes back through the filter into the flask. After extraction is complete the solvent can be removed and the desired product collected.

Everyday applications and examples

Boiling tea leaves in water extracts the tannins, theobromine, and caffeine out of the leaves and into the water, as an example of a solid-liquid extraction.

Decaffeination Decaffeination is the removal of caffeine from coffee beans, cocoa, tea leaves, and other caffeine-containing materials. Decaffeinated drinks contain typically 1–2% of the original caffeine content, and sometimes as much as 20%. Decaffeinate ...

of tea and coffee is also an example of an extraction, where the caffeine molecules are removed from the tea leaves or coffee beans, often utilising supercritical fluid extraction with CO₂ or standard solid-liquid extraction techniques.

References

External links

* {{Separation processes Analytical chemistry