Talk:Size exclusion chromatography
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[edit] Permeation and filtration?
The gel filtration chromatography page lists gel permeation chromatography as a different method. Are not gel permeation, gel filtration, gel exclusion, size exclusion, and molecular sieve all the same thing? Srnec 20:48, 14 March 2006 (UTC)
Yes, yes, yes, no, and no.
Gel permeation, filtration, exclusion are are the same. Size exclusion is a bit more general, since it doesn't require the stationary phase to be a gel. Molecular sieves can be completely different. Usually these are used in a non-chromatographic mode, and involve a certain amount of affinity (for example, using molecular sieves to dry an organic solvent).
--Takometer 04:29, 26 March 2006 (UTC)
Gel filtration chromatography refers to the Size exclusion chromatography separation of water soluble ligands in aqueous mobile phase. Gel permeation chromatography refers to the Size exclusion chromatography separation of organic soluble ligands in aqueous mobile phase.
[edit] Article cleanup
Technical jargon was a bit overused in the article, I've cut out everything that couldn't be explained or re-wrote it. The gel filtration article now redirects here and I've merged the information. I have also removed the example, as it was overly confusing and better explained by the existing article on gel filtration. A copy of the example is left here for discussion purposes:
- Let's say we have two types of particle we would like to separate, a large and a small particle. Our beads (which completey exclude the large particle) occupy 80% of the unit volume, and 50% of the beads (40% of the total volume overall) are a channel accessible to just the small particle. 25% of the beads (20% overall) are inaccessible to the small particle but accessible to solvent, and 25% is solid. Our column contains 100mL of total volume (beads + solvent), and we flow liquid through the column at .8 mL/min.
- Note that the total volume accessible to solvent is 80 mL, so it will take 100 minutes for the solvent to flow through. The small particles can access 60 mL of space, and they will elute in 75 minutes. The big particles can only see 20 mL of space, and will elute from the column in 25 minutes. Since the big particles are completely excluded from the beads, their elution volume (20mL) is known as the void volume, and the solvent volume is known as the column volume.
I feel this point is worthy of inclusion, but I don't feel confident enough in simplifying it:
- Unlike ion-exchange chromatography or affinity chromatography, SEC relies entirely on diffusion, so samples necessarily undergo a dilution, and resolution is adversely affected by increasing the injection volume. Slower solvent speeds will improve resolution to a certain point, but eventually nonspecific diffusion overtakes as a confounding factor.
I would appreciate if someone could simplify this statement and include it -- Serephine / talk - 12:07, 29 April 2006 (UTC)
[edit] References?
there are no references?? Really? --128.227.51.30 00:13, 2 July 2007 (UTC)
