Editing High-performance liquid chromatography (section)

===Particle size===
Most traditional HPLC is performed with the stationary phase attached to the outside of small spherical [[silicon dioxide|silica]] particles (very small beads). These particles come in a variety of sizes with 5&nbsp;μm beads being the most common. Smaller particles generally provide more surface area and better separations, but the pressure required for optimum linear velocity increases by the inverse of the particle diameter squared.<ref>Majors, Ronald E.. (2010-09-07) [http://www.lcgceurope.com/lcgceurope/article/articleDetail.jsp?id=333246&pageID=3# Fast and Ultrafast HPLC on sub-2 μm Porous Particles — Where Do We Go From Here? – LC-GC Europe]. Lcgceurope.com. Retrieved 2011-06-07.</ref><ref>{{cite journal|last = Xiang|first = Y. |author2=Liu Y. |author3=Lee M.L.|year=2006|title = Ultrahigh pressure liquid chromatography using elevated temperature| journal = Journal of Chromatography A|pmid = 16376355|volume = 1104|issue = 1–2|pages = 198–202|doi = 10.1016/j.chroma.2005.11.118}}</ref><ref>{{cite journal|last = Horváth|first = Cs. |author2=Preiss B.A. |author3=Lipsky S.R.|year=1967|title = Fast liquid chromatography. Investigation of operating parameters and the separation of nucleotides on pellicular ion exchangers| journal = Analytical Chemistry|pmid = 6073805|volume = 39|issue = 12|pages = 1422–1428|doi = 10.1021/ac60256a003}}</ref>

According to the equations<ref>{{Cite journal|last1=Nguyen|first1=Dao T.-T.|last2=Guillarme|first2=Davy|last3=Rudaz|first3=Serge|last4=Veuthey|first4=Jean-Luc|title=Fast analysis in liquid chromatography using small particle size and high pressure|journal=Journal of Separation Science|year=2006|language=en|volume=29|issue=12|pages=1836–1848|doi=10.1002/jssc.200600189|pmid=16970187|issn=1615-9306|doi-access=free}}</ref> of the column velocity, efficiency and [[backpressure]], reducing the particle diameter by half and keeping the size of the column the same, will double the column velocity and efficiency; but four times increase the backpressure. And the small particles HPLC also can decrease the width broadening.<ref>{{Cite journal|last1=Gritti|first1=Fabrice|last2=Guiochon|first2=Georges|title=The van Deemter equation: Assumptions, limits, and adjustment to modern high performance liquid chromatography|url=https://linkinghub.elsevier.com/retrieve/pii/S0021967313009278|journal=Journal of Chromatography A|year=2013|language=en|volume=1302|pages=1–13|doi=10.1016/j.chroma.2013.06.032|pmid=23838304|url-access=subscription}}</ref> Larger particles are used in preparative HPLC (column diameters 5&nbsp;cm up to >30&nbsp;cm) and for non-HPLC applications such as [[solid-phase extraction]].