70%?

Rae Nishi nishir at ohsu.edu
Fri Sep 22 17:52:22 EST 1995


In article <00996C7A.8F3D6147.61 at sae.ssu.umd.edu>
dte8175 at SAE.SSU.UMD.EDU ("DON ELLIS, II") writes:

> Hello,
> 
> 
> I was wondering why it has become routine to use 70% ethanol to sterilize
> equipment in the lab.  None of the other students around here know, but I'd
> be interested in finding out for myself.
> 
> Thanks in advance,
> 
> Don Ellis, II
> Salisbury State University

Boy, I really have time to kill this afternoon if I'm answering this
question...

I assume you mean 70% ethanol versus 90% or 60% rather than ethanol
versus isopropanol, etc...  40-60% ethanol will kill as effectively as
70% but you have to leave it on longer.  For some reason, ethanol
concentrations above 80% have a low efficacy, perhaps because they do
not wet as effectively.  70% ethanol will kill nearly 90% of cutaneous
bacteria within 2 min, provided the area is moist the whole time with
the alcohol.  A rapid swipe with alcohol is not very effective.  BTW it
is virtually ineffective against fungi and dried spores.  My source of
info is Goodman and Gilman (Pharmacol. Basis of Therapeutics).
 
Rae Nishi
Dept. Cell & Developmental Biology
Oregon Health Sciences University
Portland Oregon 97201
**that's Orygun, NOT Ora-Gone**



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