Extraction (chemistry)
Separation process based on solute distribution between two phases.
Extraction in chemistry is a separation process consisting of the separation of a substance from a matrix. The distribution of a solute between two phases is an equilibrium condition described by partition theory, based on exactly how the analyte moves from the initial solvent into the extracting solvent. The term washing may also refer to an extraction in which impurities are extracted from the solvent containing the desired compound.
- field
- Chemistry
- known_for
- Separation process of substances from a matrix
- types
- Liquid–liquid, acid-base, supercritical fluid, solid-liquid, solid-phase, maceration, ultrasound-assisted, microwave-assisted, heat reflux, instant controlled pressure drop, pressurized liquid, perstr
- laboratory_applications
- Separatory funnel for liquid-liquid extraction; Soxhlet extractor for solid-liquid extraction
- everyday_applications
- Boiling tea leaves, brewing coffee, oil extraction of aromas, decaffeination of tea and coffee
Lore & Background
Extraction in chemistry is defined as a separation process that isolates a substance from a matrix. The equilibrium condition governing the distribution of a solute between two phases is described by partition theory, which depends on how the analyte moves from the initial solvent into the extracting solvent. The term 'washing' may also be used when impurities are extracted from the solvent containing the desired compound. Various types of extraction exist, including liquid–liquid extraction, acid-base extraction, supercritical fluid extraction, solid-liquid extraction, solid-phase extraction, maceration (grinding), ultrasound-assisted extraction, microwave-assisted extraction, heat reflux extraction, instant controlled pressure drop extraction, pressurized liquid extraction, and perstraction.
Reader's Guide
In laboratory applications, liquid-liquid extractions typically use a separatory funnel, where two immiscible phases are combined to separate a solute from one phase into the other based on relative solubility. Common extractants can be arranged in increasing order of polarity according to the Hildebrand solubility parameter, from ethyl acetate to water. Solid-liquid extractions at laboratory scales can use Soxhlet extractors, where a solid sample is placed in a thimble and an extracting solvent is refluxed to dissolve the desired compound, which then passes through a filter into the flask. Everyday examples include boiling tea leaves in water to extract tannins, theobromine, and caffeine, as well as brewing coffee using pressurized fluid (espresso machine) or heat reflux (coffee percolator). Chefs use oil to extract aroma-bearing compounds from herbs and spices. Decaffeination of tea and coffee removes caffeine molecules, often using supercritical fluid extraction with CO2 or standard solid-liquid extraction techniques.
Did You Know?
- The distribution of a solute between two phases is an equilibrium condition described by partition theory.
- Common extractants can be arranged in increasing order of polarity according to the Hildebrand solubility parameter.
- Boiling tea leaves in water extracts tannins, theobromine, and caffeine as an example of solid-liquid extraction.
- Decaffeination of tea and coffee often utilizes supercritical fluid extraction with CO2.
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