Editing Analytical chemistry (section)

==== Chromatographic assays ====
{{further|Chromatography}}
Chromatography can be used to determine the presence of substances in a sample as different components in a mixture have different tendencies to adsorb onto the stationary phase or dissolve in the mobile phase. Thus, different components of the mixture move at different speed. Different components of a mixture can therefore be identified by their respective [[Retardation factor|R<sub>''ƒ''</sub> values]], which is the ratio between the migration distance of the substance and the migration distance of the solvent front during chromatography.
In combination with the instrumental methods, chromatography can be used in quantitative determination of the substances. Chromatography separates the analyte from the rest of the sample so that it may be measured without interference from other compounds.<ref name=":0" /> There are different types of chromatography that differ from the media they use to separate the analyte and the sample.<ref>{{Citation |last=Poole |first=C. F. |title=CHROMATOGRAPHY |date=2000-01-01 |url=https://www.sciencedirect.com/science/article/pii/B0122267702000211 |encyclopedia=Encyclopedia of Separation Science |pages=40–64 |editor-last=Wilson |editor-first=Ian D. |place=Oxford |publisher=Academic Press |language=en |isbn=978-0-12-226770-3 |access-date=2022-10-07}}</ref> In [[Thin-layer chromatography]], the analyte mixture moves up and separates along the coated sheet under the volatile mobile phase. In [[Gas chromatography]], gas separates the volatile analytes. A common method for chromatography using liquid as a mobile phase is [[High-performance liquid chromatography]].