soma
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how to prepare sand for chromatography
Anyone have information on how to prepare sand suitable for column chromatography?
Thanks.
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NEMO-Chemistry
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I asked something similar a while back, the general consensus was sand isnt a good choive.
OR
I am misreading what your asking? If you mean the sand that goes on top of the silicon then i would think depending on source (say a beach), i would
wash really well in hydrochloric acid and maybe even sulphuric if there was organics in it.
Then wash really well. I am looking at cheaper alternatives for column chromatography, so far the best i have come up with is a mention of altering
water glass (Sodium salicilicate or whatever its called).
I cant find the reference i used at the moment as i am not on main pc at the mo.
If you intend using sand for the whole column then i would think acid washes as above and ball milling very fine, but then you have the problem of
silicosis.
The other thing i have seen mentioned is cat litter! But it seems NO WHERE remotely near me sells it, all the cat litter here is the clay type.
Have a search around on here there are a couple of threads around on it.
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Ozone
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I am assuming you plan to use it to bed some other, more useful chromatographic media. We used to wash it with HCl (soak overnight in 5M), wash it
well (until pH >4), and ignite it in a furnace at 650°C for 1 hour (total about 3 Hr with heatup/cool down). The column (bed and all) should be
solvent rinsed/conditioned prior to use.
It is best to use fine sand; Florida white sand is excellent.
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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careysub
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Pottery supply outlets sell clean pure silica sand in various mesh sizes at reasonable prices. If you have a hankering for some pottery chemicals
(they are a good source of metal compounds cheap) then it is convenient to get sand also.
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Fulmen
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I would treat it with NaOH to get rid of organics, then HCL to neutralize the NaOH and dissolve anything acid soluble before ignition in a furnace. If
in doubt, wash with a suitable solvent before use.
We're not banging rocks together here. We know how to put a man back together.
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soma
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I'm wondering what is meant by "ignition in a furnace"? I don't have a furnace but could raise the temperature in a metal pan on a stove.
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Ozone
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Honestly, I don't see why you'd want to treat with alkali first (maybe to be rid of amorphous silicates/refractories and/or fines?). The HCl gets rid
of most of the mineral contaminants which are washed out. The furnace gets rid of anything organic.
By ignite they mean to go way past traditional ignition temperatures. 650°C is typical, and they are glowing at that temperature. I used large Coors
crucibles. They must be cooled slowly, or they will shatter. I don't recommend heating anything that size to glowing red heat on your kitchen stove.
It's flat-out dangerous. There are many posts on this forum dealing with improvised furnaces (electric, coal powered, and what have you); look at
those first and do it outside away from your kitchen.
Interestingly, many raw sands (even white) will be pink after ignition. Residual (intercalated, maybe) iron, perhaps. Never had a problem with it.
[edit] Prepared sand can also be purchased from chemical suppliers like Sigma or Supelco. It's nice, but it is also the most expensive sand on the
planet.
O3
[Edited on 29-7-2016 by Ozone]
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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Fulmen
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Minerals can be either be basic or acidic, if I were to go to the trouble I'd like to cover all the possibilities. It would also remove most organics,
might be some metal cations there that could survive the furnace.
We're not banging rocks together here. We know how to put a man back together.
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soma
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Quote: Originally posted by Ozone  | | I don't recommend heating anything that size to glowing red heat on your kitchen stove. It's flat-out dangerous. |
Thanks.
Could you describe what could happen that's dangerous? I heated MgO in a metal pan on a gas stove for about 30 min. at medium flame. It seems to have
hard burned the oxide (I don't, at present, have a TC to measure it) so that would mean it got to between 1000 - 1500C.
[Edited on 30-7-2016 by soma]
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Ozone
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Just standing next to a good-sized object glowing red (and I mean the whole thing, not merely the bottom) will radiate enough heat to let you know it
can be dangerous. You also cannot cool it slowly (depends on crucible material, I suppose) which could lead to vessel failure and dispersal of
material that is still quite hot enough to cause a fire.
At 1500°C and up, the thing would be glowing yellow-ish. I doubt you can hit those temperatures without insulation (firebrick, for example) with a
basic open burner on medium.
Your call, just my thoughts on the matter. I would not do this in my house unless I had a furnace.
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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soma
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The metal pan is stainless steel which melts around 1510C. I don't think a gas stove is capable of melting a stainless pan -- at least it never has
when it got left accidentally on the stove and all the water had boiled out.
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AJKOER
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I recommend following a path used to make high quality sand for photovoltaic applications (99.9999%). Namely, leach with 20% HF (caution: deadly
fumes) and let stand and rinse. Repeat with HCl and finally with aqueous NaOH.
Source: "Improvement of Impurities Removal from Silica Sand by Using a Leaching Process", full article available at: https://www.google.com/url?sa=t&source=web&rct=j&...
I would recommend, to speed up the process in a lab setting, the use of sonification. The latter can also create hydroxyl radicals to breakdown
organic matter including pollutants and the like.
[Edit] Note, all sand is not the same. Some may contain significant precipitates from organic life forms. Mineral content varies. See, for example, http://www.nature.com/scitable/blog/saltwater-science/what_i...
[Edited on 10-8-2016 by AJKOER]
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careysub
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I don't know how well the very fine form of Imsil Silica will do for chromatography (the common A-25 type sold by Axner Pottery for $2/lb is 5
microns), but if you want a source of silica of known and consistent purity at a low price you should consider this.
The Cary Company that makes it publishes a chemical analysis:
Silicon Dioxide (SiO2 ) 98.55
Aluminum Oxide (Al2O3 ) 0.85
Iron Oxide (Fe2O3 ) 0.08
Calcium Oxide (CaO) 0.03
Titanium Dioxide (TiO 2 ) 0.04
Magnesium Oxide (MgO) 0.01
Potassium Oxide (K2O) 0.08
Sodium Oxide (Na2O) 0.04
So 98.55% silica, with the part that is not silica or alumina only 0.4%.
[Edited on 10-8-2016 by careysub]
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soma
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Aldrich sells sand that is 50 - 70 mesh which is 297 -210 microns.
I would think 5 microns would probably be too small.
I've got some tan cement sand that I just soaked in muriatic acid. It's still tan though after washing.
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brubei
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In my lab (CNRS, France) we use Fontainebleau's sand, 0.06 – 0.35 mm typical silicate.
(i think your question is not about silica gel)
[Edited on 11-8-2016 by brubei]
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soma
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Right - I want to use the sand as a support under the silica gel and on top also.
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FriedBrain
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I would say boil it in a large round bottom flask with about half concentrated sulfuric acid with some hydrogen peroxide to destroy most organic
residuals and acid-soluble metal oxides. Maybe add after some boiling a bit more hydrogen peroxide, but cool it first down a bit so it does not boil
suddenly. Also I'm sure you're going to have massive problems with bumping when not well stirred (which is hard), so maybe you just want to heat
things up below the boiling point. After that I would just pour the acid off, wash several times with water and last but not least an organic solvent
like acetone and the solvent your running the column with (~ 2 times) and then just dry it in the oven.
If possible or depending on your starting sands quality getting it through a good sieve shouldn't harm.
I didn't test it though,but I think it should be fine for CC and other normal uses.
You always have time to do some chemistry, but maybe you just have other priorities?
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