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ChemWiki: The Dynamic Chemistry E-textbook > Analytical Chemistry > Instrumental Analysis > Chromatography > Liquid Chromatography > Ion Exchange Chromatography

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Ion Exchange Chromatography

 

Introduction

Imagine if we had a tube whose surfaces were coated with an immobilized cation. These would have electrostatic attraction for anions. If a solution containing a mixture of positively and negatively charged groups flows through this tube, the anions would preferentially bind, and the cations in the solution would flow through

ion_exch.jpg

  • This is the basis of ion exchange chromatography. The example above is termed "anion exchange" because the inert surface is interacting with anions
  • If the immobile surface was coated with anions, then the chromatography would be termed "cation exchange" chromatography (and cations would selectively bind and be removed from the solution flowing through
  • Strength of binding can be affected by pH, and salt concentration of the buffer. The ionic species "stuck" to the column can be removed (i.e. "eluted") and collected by changing one of these conditions. For example, we could lower the pH of the buffer and protonate anions. This would eliminate their electrostatic attraction to the immobilized cation surface. Or, we could increase the salt concentration of the buffer, the anions in the salt would "compete off" bound anions on the cation surface.

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Last Modified
17:46, 1 Oct 2013

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