Re: [Histonet] anhydrous EtOH clarification.

From:Philip Oshel


The beads are most likely either silica gel or molecular sieve. I 
don't know of specific sources in Canada, but cases of silica-gel 
beads in little capsules for drying electronics and pharmaceuticals 
can be gotten relatively cheaply from suppliers for those industries. 
I'm trying to track down such a supplier now that someone else here 
used, and if I get the information, I'll pass it on.
Molecular sieves are better, in that they have a greater capacity for 
H20. We use them routinely to keep are EtOH dry for electron 
microscopy preparation.
Molecular sieves can be purchased from industrial gas suppliers -- 
they're typically used for drying gases. Shop around, though, the 
prices can vary by a factor of 2 or more.
You want 4 Angstrom beads -- the pore size that traps H20 -- and 
preferably with some indicator beads. Get the small size beads for 
greater surface area.
Be sure to pipette from the top of the liquid if you use molecular 
sieves to avoid dust, or put the sieves in dialysis tubing.
You should also be able to get these from electron microscopy supply 
houses, but for higher prices. It's worth while doing some shopping 
on the internet.


>For laser capture the EtOH must remain 100% dry. Using a bottle of 
>regular anhydrous EtOH after it has been opened once or twice 
>sometimes has absorbed enough moisture from the air to cause 
>interferance with the LCM film and negatively affect the capture.
>I know that arcturus sells EtOH which has small beads mopping up any 
>moisture contaimination. I just don't want to keep buying a whole 
>'kit' just for 500ml's of 100% EtOH. The kit is certified RNase free 
>and works very well but not econimal for our purposes. The only 
>other source i found for this type of material no longer ships to 
>Hopefully that clears things up a little bit. As for those who wrote 
>to me explaining that 'all' EtOH is anhydrous, please excuse me for 
>assuming that you were familiar with problems facing laser capture 
>as I am sure you would have better understood the nature of my 
>Thanks again for all the help. I have learned a lot from histonet 
>over the last year, it is an excellent resource.
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Philip Oshel
Supervisor, BBPIC microscopy facility
Department of Animal Sciences
University of Wisconsin
1675 Observatory Drive
Madison,  WI  53706
voice: (608) 263-4162
fax: (608) 262-5157 (dept. fax)

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