In labs we are normally using 70% cleaning ethanol for sterilization. Can anybody know the theory behind it?
higher concentrations of ethanol evaporate very quickly. Concentrations like 95% or 90% may evaporate before than can come in contact with most of the microbial life.
Hi Suleiman,
That means higher concentration of ethanol does not participate in sterilization properly, like 70% ethanol. But we are wiping the bench tops with ethanol and use tissues to dry. That means, there we are not letting it to evaporate but we wipe it. Can you explain more?
70% ethanol is a fair enough solvent for surface disinfection as it does not make the skin dry and does not dissolve some lipids of the skin. Secondly, due to its delayed evaporation the microorganisms get a longer exposure for better inactivation (i would not like to use the word like killed or inhibited).
The % varies between 50 to 80%. the reason behind usefulness of 70% (and near to it) is that it has got more penetration power (although slow) than that of 100% ethanol. at 100% bacterial cells gets or becomes what is called 'sealed off', especially the endospores and they are not killed.
Another reason is its less in flammable and less costlier. generally hospitals use 75% while normal labs use anything between 50 to 80%. I have been using 70% ever since i started microbiology and it works fine.
Its a very good question.
Hope it clears your doubt.
Pradipta
Yes pradipta. Discussions are helpful to expand knowledge. Thank you
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