Editing High-performance liquid chromatography (section)

===Internal diameter===
[[File:Nano-LC - (1).jpg|thumb|Tubing on a nano-liquid chromatography (nano-LC) system, used for very low flow capacities]]
The internal diameter (ID) of an HPLC column is an important parameter.<ref>{{Cite journal |last1=Zelenyánszki |first1=Dóra |last2=Felinger |first2=Attila |date=2020-10-01 |title=The Impact of Column Hardware on Efficiency in Liquid Chromatography (LC) |url=https://www.chromatographyonline.com/view/the-impact-of-column-hardware-on-efficiency-in-liquid-chromatography-lc- |journal=LCGC Europe |series=LCGC Europe-10-01-2020 |language=en |volume=33 |issue=10 |pages=498–504}}</ref> It can influence the detection response when reduced due to the reduced lateral diffusion of the solute band. It can also affect the separation selectivity, when flow rate and injection volumes are not scaled down or up proportionally to the smaller or larger diameter used, both in the isocratic and in gradient modes.<ref>{{Cite journal |last=Dolan |first=John |date=2014 |title=LC Method Scaling, Part II: Gradient Separations |url=https://www.chromatographyonline.com/view/lc-method-scaling-part-ii-gradient-separations-0 |journal=LCGC North America |series=LCGC North America-03-01-2014 |language=en |volume=32 |issue=3 |pages=188–193}}</ref> It determines the quantity of analyte that can be loaded onto the column. Larger diameter columns are usually seen in preparative applications, such as the purification of a drug product for later use.<ref>{{Cite journal |last1=Jensen |first1=Ole Elvang |last2=Kidal |first2=Steffen |date=2006-03-01 |title=Using Volumetric Flow to Scaleup Chromatographic Processes |url=https://www.biopharminternational.com/view/using-volumetric-flow-scaleup-chromatographic-processes |journal=BioPharm International |series=BioPharm International-03-01-2006 |language=en |volume=19 |issue=3}}</ref> Low-ID columns have improved sensitivity and lower solvent consumption in the recent ultra-high performance liquid chromatography (UHPLC).<ref name=":2">{{Cite journal |last1=Walter |first1=Thomas H. |last2=Andrews |first2=Richard W. |date=2014 |title=Recent innovations in UHPLC columns and instrumentation |journal=Trends in Analytical Chemistry |volume=63 |pages=14–20 |doi=10.1016/j.trac.2014.07.016 |issn=0165-9936|doi-access=free }}</ref>

Larger ID columns (over 10&nbsp;mm) are used to purify usable amounts of material because of their large loading capacity.

Analytical scale columns (4.6&nbsp;mm) have been the most common type of columns, though narrower columns<ref name=":2" /> are rapidly gaining in popularity. They are used in traditional quantitative analysis of samples and often use a [[spectrophotometer|UV-Vis absorbance detector]].

Narrow-bore columns (1–2&nbsp;mm) are used for applications when more sensitivity is desired either with special UV-vis detectors, [[fluorescence]] detection or with other detection methods like [[liquid chromatography-mass spectrometry]]

Capillary columns (under 0.3&nbsp;mm) are used almost exclusively with alternative detection means such as [[mass spectrometry]]. They are usually made from [[fused silica]] capillaries, rather than the stainless steel tubing that larger columns employ.