Methanol in ethanol

Richard Kerr kerrr at CRYPTIC.RCH.UNIMELB.EDU.AU
Mon Apr 6 19:41:03 EST 1998


At 09:05 6/04/98 -0700, you wrote:
>Colleagues:
>
>Like you we use ethanol for DNA or RNA precipitation and 
>washing of the pellet prior to drying by vacuum. Our Stores recently 
>switched to " 95% " ethanol which turns out to have a lot of methanol 
>in it (ethanol:methanol is 84:16). We plan to switch back to ethanol.

Hey Doug,
our store has done the same thing....something to do with 'safety guidelines'
It sounds like your stores people have just picked a 'dud' brand of 95%
EtOH...possibly you could get another few brands in and check them then
nominate your preferred brand.  This would keep them, you and your nucleic
acid happy.

>But, in addition to the question of safety now that the "ethanol" 
>contains "methanol" we are worried about our experiments using this 
>grade of "ethanol". Would nucleic acids prepared with ethanol/methonl 
>mixtures contain any residues after drying that may interfere with 
>the usual techniques e.g., restriction, PCR, RT-PCR etc.?

I suspect that this would only be a problem if the methanol precipitated a
chemical that the ethanol did not....which is not that likely given that the
difference in chain length between them is small.    Both are quite labile
and dry down nicely, even at RT.  The issue I see causing you concern may be
that the '95% EtOH' does not ppt DNA/RNA as efficiently (as you say, it is
only really 84% EtOH)..increasing the volume that you use in your PPTN step
should counter this issue.  

seeya 
R

Richard Kerr.
The Murdoch Institute,
R.C.H. Flemington Rd, Parkville, 3052,
AUSTRALIA.
kerrr at cryptic.rch.unimelb.edu.au
Phone (61) 3 9345 5045.
FAX   (61) 3 9348 1391.
'The most interesting things about vertebrates occur in the neural crest.'
	Peter Thorogood.




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