95% ethanol vs 100% ethanol for DNA extraction - (May/21/2007 )
Hi all: my lab primarily uses the Qiagen DNEasy Tissue kit (spin column format) for extractions. The extraction protocol is like others in that it recommends that you use 96-100% ethanol. In my lab we only have access to 95% ethanol, so that is what we use. I would like to hear from others if there is enough difference in extraction results (DNA yield or effects of inhibitors) when using 100% ethanol compared to 95%. I am trying to convince my lab manager to switch over. If anybody has a clear argument I can make, I'd appreciate the help. I'm new to molecular biology so my background knowledge is a bit spotty.
Thanks,
Angela
I think that it makes almost no difference -- practically the minute you open the bottle of "100%" ethanol it becomes less than 100% anyway -- in fact we routinely avoid using "100%" ethanol because in order to get this "100%" you have do do a drying of the ethanol with i think its benzene? to remove the water-- anyway now you have benzene contamination rather than H2O so why not get the "pure" stuff straight from the distillation at 95%? basically I think people usually mean this when they say 100% EtOH anyways...
HTH -- someone else correct me if I have said something wrong...
i never used 95% ethanol, but now i am interested to do a experiment to precipitate DNA with 95% and 100% ethanol, and check/compare the result 
Dear T. reesei
100% ethanol is not exist. Because during distillation ethanol form with water azeotrope mixture. To reach 98 % ethanol one make distillation with benzol as Beccaf22 said. So you will use 98% ehanol with benzol contaminant, it is suitable for you?
It's possible to get absolutely 100% ethanol using a material called a 'molecular sieve' to filter the water out. But it's very expensive.
But anyway, I interpret 95% ethanol = 100% ethanol or just call it "ethanol" for all intents and purposes. I believe that 97.7% is a very common purity for labs, so that's probably what most of it is 