The key difference between ion exchange and size exclusion chromatography is that ion exchange chromatography is used to analyze ionic substances according to the charge whereas size exclusion chromatography is used to analyze large molecules according to the size.
Chromatography is an analytical technique that can be used to analyze different mixtures. The chromatographic techniques are named according to the parameter used to analyze the substances – e.g. size exclusion chromatography, ion exchange chromatography, etc.
CONTENTS
1. Overview and Key Difference
2. What is Ion Exchange Chromatography
3. What is Size Exclusion Chromatography
4. Side by Side Comparison – Ion Exchange vs Size Exclusion Chromatography in Tabular Form
5. Summary
What is Ion Exchange Chromatography?
Ion exchange chromatography is an analytical technique in which we can analyze ionic substances. It is often useful to analyze inorganic anions and cations (i.e. chloride and nitrate anions and potassium, sodium cations). Although it is not a very common method, we can analyze organic ions using it. Moreover, we can use this technique for the purification of proteins because proteins are charged molecules at certain pH values. Here, we use a solid stationary phase to which the charged particles can attach. For example, we can use the resin polystyrene-divinylbenzene copolymers as solid support.
Figure 01: Theory behind Ion Exchange Chromatography
To explain this further, the stationary phase has fixed ions such as sulfate anions or quaternary amine cations. Each of these should associate with a counter ion (an ion with opposite charge) if we are to maintain the neutrality of this system. If the counter ion is a cation, then we name the system as a cation exchange resin. But, if the counterion is an anion, the system is an anion exchange resin. Moreover, there are five major steps in ion-exchange chromatography:
- Initial stage
- Adsorption of the target
- Starting of elution
- End of elution
- Regeneration
What is Size Exclusion Chromatography?
Size exclusion chromatography or SEC is an analytical technique in which molecules in a mixture can be separated by their size and molecule weight. Usually, it works with large molecules called macromolecules. Typically, an aqueous solution is used for the analysis. Then it is called the gel filtration chromatography. When an organic solvent, it is called gel permeation chromatography.
Gel filtration chromatography is a form of size exclusion chromatography in which we use an aqueous solution as the mobile phase. Therefore, the mobile phase we often use in this technique is an aqueous buffer. Also, we use a chromatographic column for this separation, and we need to pack the column with porous beads. Usually, Sephadex and agarose are useful as the porous material. Hence, these material are the stationary phase of our experiment. Moreover, we can use the pore size of these beads to determine the size of macromolecules that we are separating. However, it is just an estimation.
Figure 02: An Apparatus for Size Exclusion Chromatography
Gel permeation chromatography is a form of size exclusion chromatography in which we use an organic solvent as the mobile phase. Therefore, we can use solutions such as hexane and toluene for this purpose. The stationary phase is a porous material, the same as in gel filtration chromatography. This technique is often applied to polymers and other organic-soluble material. The method of action of the technique is similar to that of gel filtration chromatography.
What is the Difference Between Ion Exchange and Size Exclusion Chromatography?
Chromatography is an analytical technique that can be used to analyze different mixtures. The key difference between ion exchange and size exclusion chromatography is that ion exchange chromatography is used to analyze ionic substances according to the charge whereas size exclusion chromatography is used to analyze large molecules according to the size.
Below infographic gives more information about the difference between ion exchange and size exclusion chromatography.
Summary – Ion Exchange vs Size Exclusion Chromatography
Chromatography is an analytical technique that can be used to analyze different mixtures. The key difference between ion exchange and size exclusion chromatography is that ion exchange chromatography is used to analyze ionic substances according to the charge whereas size exclusion chromatography is used to analyze large molecules according to the size.
Reference:
1. “Size-Exclusion Chromatography.” Wikipedia, Wikimedia Foundation, 7 Apr. 2020, Available here.
Image Courtesy:
1. “Ion exchange” By Jspiteri at English Wikibooks – Transferred from en.wikibooks to Commons (Public Domain) via Commons Wikimedia
2. “Size Exclusion Chromatography Apparatus” By Kjaergaard at English Wikipedia – Transferred from en.wikipedia to Commons by Jacopo Werther. (Public Domain) via Commons Wikimedia
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