Editing High-performance liquid chromatography (section)

===Partition chromatography===
[[File:HILIC Partition Method Graphic.png|thumb|300px|[[HILIC]] partition technique useful range]]
Partition chromatography was one of the first kinds of chromatography that chemists developed, and is barely used these days.<ref>{{Cite journal| volume = 19| issue = 5| pages = 506–512| last = Ettre| first = C.| title = Milestones in Chromatography: The Birth of Partition Chromatography| journal = LCGC| access-date = 2016-02-26| date = 2001| url = http://images.alfresco.advanstar.com/alfresco_images/pharma/2014/08/22/1598ed6f-5bbe-400b-bc08-ff07d2c59826/article-2090.pdf| archive-date = 2016-03-04| archive-url = https://web.archive.org/web/20160304170852/http://images.alfresco.advanstar.com/alfresco_images/pharma/2014/08/22/1598ed6f-5bbe-400b-bc08-ff07d2c59826/article-2090.pdf| url-status = dead}}</ref> The [[partition coefficient]] principle has been applied in [[paper chromatography]], [[thin layer chromatography]], [[gas phase]] and [[countercurrent chromatography|liquid–liquid separation]] applications. The 1952 [[Nobel Prize]] in chemistry was earned by [[Archer John Porter Martin]] and [[Richard Laurence Millington Synge]] for their development of the technique, which was used for their separation of [[amino acids]].<ref>{{Cite journal| volume = 35| issue = 1–2| pages = 91–121| last1 = Martin| first1 = A J P| last2 = Synge| first2 = R L M| title = Separation of the higher monoamino-acids by counter-current liquid-liquid extraction: the amino-acid composition of wool| journal = Biochemical Journal| date = 1941| pmid = 16747393| doi=10.1042/bj0350091| pmc=1265473}}</ref> Partition chromatography uses a retained solvent, on the surface or within the grains or fibers of an "inert" solid supporting matrix as with paper chromatography; or takes advantage of some [[coulombic]] and/or [[hydrogen donor]] interaction with the stationary phase. Analyte molecules partition between a liquid stationary phase and the eluent. Just as in [[HILIC|hydrophilic interaction chromatography]] (HILIC; a sub-technique within HPLC), this method separates analytes based on differences in their polarity. HILIC most often uses a bonded polar [[Stationary phase (chemistry)|stationary phase]] and a mobile phase made primarily of [[acetonitrile]] with water as the strong component. Partition HPLC has been used historically on unbonded silica or alumina supports. Each works effectively for separating analytes by relative polar differences. HILIC bonded phases have the advantage of separating [[acidic]], [[Base (chemistry)|basic]] and neutral solutes in a single chromatographic run.<ref>{{cite book|year=1987 |title=High performance liquid chromatography |url=https://archive.org/details/highperformancel00lind |url-access=registration |publisher=Wiley |author1=Lindsay, S. |author2=Kealey, D. |osti = 7013902}} from review {{cite journal|journal=J. Am. Chem. Soc. |volume=110 |issue=11 |year=1988 |doi=10.1021/ac00162a003|title=Theoretical and experimental foundation for surface-coverage programming in gas–solid chromatography with an adsorbable carrier gas|last1=Hung|first1=L. B.|last2=Parcher|first2=J. F.|last3=Shores|first3=J. C.|last4=Ward|first4=E. H.|pages=1090–1096}}</ref>

The polar analytes diffuse into a stationary water layer associated with the polar stationary phase and are thus retained. The stronger the interactions between the polar analyte and the polar stationary phase (relative to the mobile phase) the longer the elution time. The interaction strength depends on the functional groups part of the analyte molecular structure, with more polarized groups (''e.g.'', hydroxyl-) and groups capable of hydrogen bonding inducing more retention. [[Coulombic]] (electrostatic) interactions can also increase retention. Use of more polar solvents in the mobile phase will decrease the retention time of the analytes, whereas more hydrophobic solvents tend to increase retention times.{{citation needed|date=July 2024}}