why 70% ethanol but not absolute ethanol

[leekaming]

We often use 70% ethanol in routine lab antiseptic. Can we use 100% ethanol instead? If not, why?
what is the mechanism behind?

[relaxin]

I was once told that 70% ethanol is more effective in lysing bacteria than absolute ethanol. This was determined empirically.

[r.rosati]

What passes from generation to generation of researchers is that 100% ethanol dehydrates instead of lysing, and some microrganisms might survive this.
But if you end up with an actual reference for this, I'd be curious heheh.

[Astarte]

I've always been told that absolute ethonal evaporates too quickly to kill off the microorganisms completely, but sorry no references.

[r.rosati]

Take a look at this reference, it's not a plenary paper on ethanol disinfection :) but it's something:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC88911/

[Astarte]

Hey, and there is a reference in there supporting the evaporation theory! Increasing evaporation time increases the antimicorbial activity of the alcohol!

[GelBandIt]

As further evidence that 100% ethnaol and 70% ethanol have different properties, paper chromatography of black sharpie ink (or attempting to erase it form a plastic surface) will reveal that there is at least one component of black sharpie ink that is soluble in 100% ethanol but not 70% ethanol. 100% ethanol removes sharpie completely.

Maybe this has something to do with the way it interacts with the cell membrane.

[memari]

This old link maybe is useful.

http://molecularbiology.forums.biotechniques.com/viewtopic.php?f=8&t=13785


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Babak

[simonclark]

Take a look at this reference, it's not a plenary paper on ethanol disinfection but it's something:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC88911/

absolute ethanol evaporate very easily and quickly ...so use 70% ethanol but not absolute one .