Ion exclusion chromatography

Ion exclusion chromatography is a technique,introduced by Wheaton and Bauman, used to separate ionic compounds from non-ionic compounds and to separate mixtures of acids.

1. PREPARED BY ANUSREE V SECOND SEMESTER M.PHARM PHARMACEUTICAL CHEMISTRY AL SHIFA COLLEGE OF PHARMACY ION EXCLUSION CHROMATOGRAPHY

2. OTHER NAMES Ion exclusion partition chromatography Ion chromatography – Exclusion mode Donnan exclusion chromatography 2

3. INTRODUCTION First introduced by Wheaton and Bauman in 1953. IEC is a technique used to separate ionic compounds from non-ionic compounds and to separate mixtures of acids. 3

4. PRINCIPLE Ionic substances pass quickly through the column. Non-ionic (molecular) or partially ionized substances are held up and are eluted more slowly. Functions by Donnan exclusion mechanism . Mobile phase- liquid (water or aqueous acid or base) Stationary phase- ion exchange resins Cationic Anionic 4

5. FEATURES CATIONIC EXCHANGE RESIN ANIONIC EXCHANGE RESIN Counter ion Positively charged Negatively charged Fixed ion Negatively charged Positively charged Examples CMC Diethyl aminoethyl(DEAE), Triethyl aminoethyl(TEAE) Figure 5

6. Chromatographic system consists of 3 phases. Mobile phase Resin phase Occluded liquid phase The mobile phase passes through the interstitial volume existing between the beads of the ion-exchange resin. The resin phase is the solid resin network and functionalized groups, which can be considered to be a semipermeable ion- exchange membrane separating the flowing mobile phase from the stationary occluded liquid inside the resin. 6

7. An occluded liquid phase is formed by mobile phase that becomes trapped within the pores of the resin phase. This trapped liquid acts as the stationary phase of the system. When the column is filled with water, pumped through as a mobile phase, the water molecules accumulate as hydration spheres around the dissociated functional groups of the support. Water contained in the pores of the support and in the hydration spheres is immobilized, thus forming the stationary phase. 7

8. The commonly accepted retention mechanism of IEC involves the formation of a pseudo semi-permeable membrane around the resin stationary phase. The ion exclusion process relies on the establishment of an electrical potential between a dil. MP and a stationary phase of high ion exchange site concentration. Ionic solutes of similar charge to the stationary phase (generally sulfonated cation exchangers are used for weak acid analytes), experience repulsion from the resin surface, where as neutral species can penetrate the resins pores and stationary occluded phase, thus experiencing retention. 8

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10. Thus, analytes are separated by : Exclusion or repulsion if they are ionized and have the same charge as the resin. Adsorption if they are non-polar or partially ionized. 10

11. ADVANTAGES  The eluent is water or aqueous acid or base with little or no organic modifier, which offers environmental and economic benefits in addition to compatibility with aqueous sample matrices. Difficult separations such as simple aliphatic carboxylic acids (e.g., formate, acetate, propionate and butyrate) are possible. 11

12. It is compatible with a wide range of detection methods. The columns can be ion exchange columns, reversed-phase or normal-phase columns, or dynamically modified reversed-phase with an ion pairing agent. It is stable for long-term analysis of complex samples such as wine or mustard. 12

13. INSTRUMENTATION 13

14. The typical ion chromatograph consists of an eluent generator or an eluent reservoir with degassing facilities. An eluent delivery system including an isocratic or a gradient high-pressure pump, sample pretreatment and injection system, which is either a manual valve or an autosampler. A separation column. Column packed with stationary phase material. 14

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16. A detection system, which includes modification of the effluent composition to achieve better selectivity or sensitivity. 16

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19. 19 A data acquisition system, which is mainly based on personal computers. The main feature of typical IC instrumentation is the suppression system allowing the decrease of background conductivity of the effluent and providing better sensitivity for conductimetric detection.

20. APPLICATIONS Technique is mainly used for the separation of weak acids, particularly carboxylic acids, but has also been applied to the separation of carbohydrates, phenols and amino acids and can also be used for the separation of weak bases. 20

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27. REFERENCE Skoog, Holler, Crouch; Instrumental Analysis. Bronislaw Krzysztof Glod, Principles and appications of ion exclusion chromatography, Acta chromatographica, January 1997. K.L. Ng, P.R. Haddad; ACIDS/Liquid chromatography; Encyclopedia Separation Science,2000. 27

28. Yal Yashin and A Ya Yashin , HF Walton; Ion exchange/Ion chromatography instrumentation. Bronislaw Krzysztof Glod , Marc Baumann; A theoretical explanation for the retention mechanism of ion exclusion chromatography; 12 May 2003. Fotouh R. Mansour Christine L. Kirkpatrick  Neil D. Danielson; Ion Exclusion Chromatography of Aromatic Acids; Journal of Chromatographic Science , Volume 51, Issue 7, August 2013, Pages 655–665. www.chrom-china.com quimica.udea.edu.co 28

29. 29 www.semanticscholar.org K. Tanaka, P.R. Haddad, Ion exlcusion chromatography: liquid chromatography ; Encyclopedia of Separation Science , 2000. B. Paull, P.N.  Nesterenko , in  Liquid Chromatography: Fundamentals and Instrumentation , 2013

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