From Wikipedia, the free encyclopedia
Separation of a desired substance from other substances in the sample
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. 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
.
Laboratory applications and examples
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]
Liquid-liquid extractions in the laboratory usually make use of a
separatory funnel
, where two
immiscible
phases are combined to separate a
solute
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.
[1]
[2]
Common extractants may be arranged in increasing order of polarity according to the
Hildebrand solubility parameter
:
ethyl acetate
<
acetone
<
ethanol
<
methanol
< acetone:water (7:3) < ethanol:water (8:2) < methanol:water (8:2) <
water
Solid-liquid extractions at laboratory scales can use
Soxhlet extractors
. 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
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]
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
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 CO
2
or standard solid-liquid extraction techniques.
[3]
See also
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References
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]
Further reading
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]
- Fundamentals of Analytical Chemistry
(8th ed.).
- Gunt Hamburg, 2014, Thermal Process Engineering: Liquid-liquid extraction and solid-liquid extraction, see
[1]
, accessed 12 May 2014.
- Colin Poole & Michael Cooke, 2000, Extraction, in Encyclopedia of Separation Science, 10 Vols.,
ISBN
9780122267703
, accessed 12 May 2014.
- Stevens, G.W.; Lo, Teh C.; Baird, Malcolm H. I. (2007). "Extraction, Liquid-Liquid".
Kirk-Othmer Encyclopedia of Chemical Technology
(1 ed.). Wiley.
doi
:
10.1002/0471238961.120917211215.a01.pub2
.
ISBN
978-0-471-48494-3
. Retrieved
12 May
2014
.
- Voeste, T.; Weber, K.; Hiskey, B.; Brunner, G. (2006). "Liquid?Solid Extraction".
Ullmann's Encyclopedia of Industrial Chemistry
(1 ed.). Wiley.
doi
:
10.1002/14356007.b03_07.pub2
.
ISBN
978-3-527-30385-4
.
doi
:
10.1002/14356007.b03_07.pub2
. Retrieved
12 May
2014
.
- R. J. Wakeman, 2000, "Extraction, Liquid-Solid", in Kirk-Othmer Encyclopedia of Chemical Technology,
doi
:
10.1002/0471238961.1209172123011105.a01
, accessed 12 May 2014.
- M.J.M. Wells, 2000, "
Essential guides to method development in solid-phase extraction
," in
Encyclopedia of Separation Science
, Vol. 10 (I.D. Wilson, E.R. Adlard, M. Cooke, and C.F. Poole, eds.), London:Academic Press, London, 2000, pp. 4636?4643.
ISBN
978-0122267703
External links
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