Editing High-performance liquid chromatography (section)

=== Aqueous normal-phase chromatography ===
'''Aqueous normal-phase chromatography''' ('''ANP''') is also called '''hydrophilic interaction liquid chromatography''' ('''HILIC''').<ref name=":1">{{Cite journal |last=McCalley |first=David V. |date=2017-11-10 |title=Understanding and manipulating the separation in hydrophilic interaction liquid chromatography |url=https://pubmed.ncbi.nlm.nih.gov/28668366/ |journal=Journal of Chromatography A |volume=1523 |pages=49–71 |doi=10.1016/j.chroma.2017.06.026 |issn=1873-3778 |pmid=28668366}}</ref> This is a chromatographic technique which encompasses the mobile phase region between reversed-phase chromatography (RP) and organic normal phase chromatography (ONP). HILIC is used to achieve unique selectivity for hydrophilic compounds,<ref name="doi.org">{{Cite journal |last1=Buszewski |first1=Bogusław |last2=Noga |first2=Sylwia |date=2012 |title=Hydrophilic interaction liquid chromatography (HILIC)—a powerful separation technique |url=https://doi.org/10.1007/s00216-011-5308-5 |journal=Analytical and Bioanalytical Chemistry |language=en |volume=402 |issue=1 |pages=231–247 |doi=10.1007/s00216-011-5308-5 |issn=1618-2650 |pmc=3249561 |pmid=21879300}}</ref> showing normal phase elution order, using "reversed-phase solvents", i.e., relatively polar mostly non-aqueous solvents in the mobile phase.<ref name=":1" /> Many biological molecules, especially those found in biological fluids, are small polar compounds that do not retain well by reversed phase-HPLC. This has made hydrophilic interaction LC (HILIC) an attractive alternative and useful approach for analysis of polar molecules. Additionally, because HILIC is routinely used with traditional aqueous mixtures with polar organic solvents such as ACN and methanol, it can be easily coupled to MS.<ref name="doi.org"/>