Sciencemadness Discussion Board

Column chromatography materials

Paddywhacker - 19-4-2010 at 02:27

I tried to make a granulated corn-starch chromatography medium by moistening 90% corn starch + 10% plaster of paris, letting it dry out, and then grinding it and fractionating it by using sieves of different size.

But the dried mixture just crumbled back to a too-fine powder. I thought I'd ask here before wasting any more time and materials.

Has anybody any experience or advice on home-made chromatography packings?

Starch from the grocery shop, as well as silica and alumina flour from the pottery supplies are all too fine and they cake up and block a chromatography column. Packing materials have to be granular, with a limited range of particle sizes. How to go from the fine powder to the granules is the question.

Pomzazed - 19-4-2010 at 02:35

I tend to use the cat-pee sand of the cheapest price bought from the supermarket. It works like silica 60 but you'll need twice or thrice the length of the column for separation. (I use a burette as a column!).

Edit: smaller particle pack like starch may need some pump. Aquarium air pump works fine here :) I tend to dry the solvent under baked MgSO4 overnight and oven-dried the starch at low temp to make an anhydrous condition, which prevent the starch from clogging to gel-like substance.

[Edited on 19-4-2010 by Pomzazed]

DJF90 - 19-4-2010 at 09:00

All the chromatography silica I've used is so fine it goes *everywhere* if you not careful and work with it in the hood. Bear in mind that chromatography is naturally painfully slow, hence the modernisation to flash chromatography. I advise you get a set of bellows... IIRC particle size is between 30 and 60nm?

unionised - 19-4-2010 at 10:30

I doubt anyone is using particles that small. HPLC uses particles of about 2 to 10 microns. 30 to 60 microns is a bit more like it for ordinary chromatography.

DJF90 - 19-4-2010 at 10:42

Sorry yes, three powers of ten out that is! should be 30-60um!

Paddywhacker - 19-4-2010 at 13:31

Ground up kitty litter sounds like an interesting experiment.

I have 50 mesh, 100 mesh and 200 mesh sieves from a pottery supplies place for fractionating the material. 50 to 100 mesh would be good for gravity-fed column chromatography. You could do the same, Pomzazed, and get better performance.

benzylchloride1 - 20-4-2010 at 09:16

Quote: Originally posted by Pomzazed  
I tend to use the cat-pee sand of the cheapest price bought from the supermarket. It works like silica 60 but you'll need twice or thrice the length of the column for separation. (I use a burette as a column!).

Edit: smaller particle pack like starch may need some pump. Aquarium air pump works fine here :) I tend to dry the solvent under baked MgSO4 overnight and oven-dried the starch at low temp to make an anhydrous condition, which prevent the starch from clogging to gel-like substance.

[Edited on 19-4-2010 by Pomzazed]


A question on "kitty litter chromatography" What brand do you use for column chromatography and does it have anything beside silica in it? I like this idea since I am looking for a dirt cheap stationary phase for column chromatography. I do not want to pay $300 per kilogram from Aldrich.

[Edited on 20-4-2010 by benzylchloride1]

aonomus - 20-4-2010 at 09:52

If you want to do reverse phase chromatography, silica gel coated in heavy paraffin oil was the old school technique prior to silanization with alkyl group substituted silyl chlorides. I recall reading somewhere that CaCO3 and CaCO3 reverse phase have also been done, but likely at much lower separation efficiency and low plate numbers.

smaerd - 22-3-2011 at 12:14

Ideally I'd like to figure out a 'decent' affordable OTC stationary phase as well. Some pottery stores sell silica flint 200 and/or 350 mesh. Does this not work because it isn't silica 'gel' and is just silica? The nomenclature of all the sillica's/sillicate's is a bit befuddling for me it's hard to figure it all out. From what I've read 'flint' is just a pottery word. So it's just silica granules at a set size?

Another idea is(sorry if theres a few things slightly off here it's just the quick run down didn't really check the 'work'):
SiO2(aq) + NaOH(aq) -Heat-> Na2(SiO3)
Na2SiO3 + 2HCl -> 2NaCl + H2SiO3
H2SiO3 -heat> SiO2(silica gel?) + H2O

This should work as well but would be a serious pain in the @&#. Lots of heating conc. NaOH, cleaning, etc. Then mashing and filtering through ''expensive'' micron screens using a respirator/dust mask...

I've heard of people using things like diatomaceous earth, but that has to be messy and inconsistent. hmmm...

phlogiston - 22-3-2011 at 15:11

Cheap kitty litter consists mostly of bentonite.
I never used it for chromatography, but have used the stuff for other purposes. Grinding it is a pain in the *, so I've switched to powdered bentonite from a ceramics supply store.

smuv - 22-3-2011 at 16:04

Some brands of kitty litter are pretty much just beads of silica gel. Look for litters with "crystals" in the name. I would imagine that if you pulverized that silica gel (after removing any impurities, which should be doable by hand) you would get decent column performance.

Diatomaceous earth/celite sucks for chromatography! You will get very bad separations. Generally I use these things as solid supports for the very purpose that things don't really tend to stick to them very readily.

smaerd - 3-4-2011 at 17:14

What about cellulose? Someone mentioned this on another forum, and it seems cheap enough to work for TLC plates and column work. Would it give decent separations?

Actually I'm going to give some bentonite a shot it's cheap enough so why not.

[Edited on 4-4-2011 by smaerd]