Ion Chromatography 1787246 225498478 2008-07-14T00:37:56Z TimVickers 1635280 /* Separating Proteins */ add image {{Infobox chemical analysis | name = Ion exchange chromatography | image = Metrohm_850.jpg | caption = Ion chromatography workstation | acronym = IC | classification =[[Chromatography]] | analytes = | manufacturers = [http://www.dionex.com Dionex Corp.], [http://www.lachatinstruments.com Lachat Instruments], [http://www.metrohm.com Metrohm, Ltd.] | related = [[High performance liquid chromatography]]<br>[[Aqueous Normal Phase Chromatography]]<br>[[Size exclusion chromatography]]<br>[[Micellar liquid chromatography]] | hyphenated = }} '''Ion-exchange chromatography''' (or ''ion chromatography'') is a process that allows the separation of [[ion]]s and [[polar molecule]]s based on the charge properties of the molecules. It can be used for almost any kind of charged molecule including large [[proteins]], small [[nucleotides]] and [[amino acid]]s. The solution to be injected is usually called a ''sample'', and the individually separated components are called ''analytes''. It is often used in protein purification, water analysis, and quality control. == History == Ion methods have been in use since 1850, when H. Thompson and J. T. Way, researchers in England, treated various clays with ammonium sulfate or carbonate in solution to extract the ammonia and release calcium. In 1927, the first zeolite mineral column was used to remove interfering calcium and magnesium ions from solution to determine the sulfate content of water. The modern version of IEC was developed during the wartime Manhattan Project. A technique was required to separate and concentrate the radioactive elements needed to make the atom bomb. Researchers chose adsorbents that would latch onto charged transuranium elements, which could then be differentially eluted. Ultimately, once declassified, these techniques would use new IE resins to develop the systems that are often used today for specific purification of biologicals and inorganics. In the early 1970s, ion chromatography was developed by Hamish Small and co-workers at Dow Chemical Company as a novel method of IEC usable in automated analysis. IC uses weaker ionic resins for its stationary phase and an additional neutralizing stripper, or suppressor, column to remove background eluent ions. It is a powerful technique for determining low concentrations of ions and is especially useful in environmental and water quality studies, among other applications. The [[Dow Chemical|Dow Chemical Company]] technology was acquired by Durrum Instrument Corp. (maker of the [[Durrum D-500]]), which later formed a separate business unit for its new IC products, naming it Dionex ('''D'''ow '''Ion''' '''Ex'''change). [[Dionex Corporation]] was incorporated in Sunnyvale, California in 1980, and, led by A. Blaine Bowman, purchased the Dionex assets. ==Principle== [[Image:Ion_chromatogram.JPG|thumb|450px|right|Ion Chromatogram]] Ion exchange chromatography retains [[analyte]] molecules based on [[Coulomb's law|coulombic]] (ionic) interactions. The stationary phase surface displays ionic functional groups (R-X) that interact with analyte ions of opposite charge. This type of chromatography is further subdivided into cation exchange chromatography and anion exchange chromatography. The ionic compound consisting of the cationic species M+ and the anionic species can be retained by the stationary phase. Cation exchange chromatography retains positively charged [[cation]]s because the stationary phase displays a negatively charged functional group: <math>\text{R-X}^-\text{C}^+\,+\, \text{M}^+ \, \text{B}^- \rightleftarrows \,\text{R-X}^-\text{M}^+ \,+\, \text{C}^+ \,+\, \text{B}^-</math> Anion exchange chromatography retains anions using positively charged functional group: <math>\text{R-X}^+\text{A}^-\,+\, \text{M}^+ \, \text{B}^- \rightleftarrows \,\text{R-X}^+\text{B}^- \,+\, \text{M}^+ \,+\, \text{A}^-</math> Note that the ion strength of either C+ or A- in the mobile phase can be adjusted to shift the equilibrium position and thus retention time. The ion chromatogram shows a typical chromatogram obtained with an anion exchange column. == Separating Proteins == [[Image:Ion exchange column.jpg|thumb|left|Preparative-scale ion exchange column used for [[protein purification]].]] Proteins have numerous functional groups that can have both positive and negative charges. Ion exchange chromatography separates proteins according to their net charge, which is dependent on the composition of the mobile phase. By adjusting the pH or the ionic concentration of the mobile phase, various protein molecules can be separated. For example, if a protein has a net positive charge at pH 7, then it will bind to a column of negatively-charged beads, whereas a negatively charged protein would not. By changing the pH so that the net charge on the protein is negative, it too will be eluted. Elution by changing the ionic strength of the mobile phase is a more subtle effect - it works as ion from the mobile phase will interact with the immobilized ion in preference over those on the stationary phase. This "shields" the stationary phase from the protein, (and vice versa) and allows the protein to elute. ==Typical Technique== [[Image:ICS-3000.jpg|thumb|right|300 px|Another Ion Chromatography Workstation]] A sample is introduced, either manually or with an autosampler, into a sample loop of known volume. A [[buffer solution|buffered]] aqueous solution known as the mobile phase carries the sample from the loop onto a column that contains some form of stationary phase material. This is typically a resin or gel matrix consisting of [[agarose]] or [[cellulose]] beads with [[Covalent bond|covalently]] bonded charged functional groups. The target analytes (anions or cations) are retained on the stationary phase but can be eluted by increasing the concentration of a similarly charged species that will displace the analyte ions from the stationary phase. For example, in cation exchange chromatography, the positively charged analyte could be displaced by the addition of positively charged sodium ions. The analytes of interest must then be detected by some means, typically by conductivity or UV/Visible light absorbance. In order to control an IC system, a Chromatography Data System (CDS) is usually needed. In addition to IC systems, some of these CDSs can also control Gas Chromatography (GC) and HPLC systems. ==Manufacturers of Ion Chromatographs== *[http://www.dionex.com Dionex Corp.] *[http://www.lachatinstruments.com Lachat Instruments] *[http://www.metrohm.com Metrohm, Ltd.] === Manufacturers of Ion Chromatography Accessories and Columns === *[[Phenomenex]] *[http://www.hamiltoncompany.com/HPLC/hplcindex.asp Hamilton Company] *[[CryoBioPhysica, Inc.]] ==References== *'''Ion Chromatography '''by Hamish Small ISBN 0-306-43290-0''' *'''Handbook of Ion Chromatography''' by Joachim Weiss, Dionex Corporation, ISBN 978-3527287017 *'''Ion Chromatography''' by James S. Fritz and Douglas T. Gjerde, ISBN 3527299149 *'''Ion Chromatography (Journal of Chromatography Library)''' by P.R. Haddad and P.E. Jackson, ISBN 0444882324 *'''Practical Ion Chromatography''' by C. Eith, M. Kolb, A. Seubert, K. Viehweger, [http://www.metrohm.com Metrohm AG], Order Number [http://products.metrohm.com/SearchResult.aspx?searchText=8.792.5013 8.792.5013] (Free Monograph) *'''Sample Preparation Techniques for Ion Chromatography''' by A. Seubert et al., [http://www.metrohm.com Metrohm AG], Order Number [http://products.metrohm.com/SearchResult.aspx?searchText=8.025.5003 8.025.5003] (Free Monograph) *'''Air Monitoring by Ion Chromatography''' by M. Läubli, D. Parab, K. Viehweger, [http://www.metrohm.com Metrohm AG], Order Number [http://products.metrohm.com/SearchResult.aspx?searchText=8.035.5003 8.035.5003] (Free Monograph) ==See also== *[[Isoelectric point]] *[[High performance liquid chromatography]] [[Category:Chromatography]] [[bs:Ionoizmjenjivačka hromatografija]] [[cs:Ionexová chromatografie]] [[de:Anionenaustauschchromatografie]] [[es:Cromatografía líquida]] [[it:Cromatografia a scambio ionico]] [[ja:イオンクロマトグラフィー]] [[ru:Ионообменная хроматография]] [[sv:Jonbyteskromatografi]]