I recently had a discussion about making a 70% ethanol solution to clean workbenches in a lab where people work with bacteria. My question now is: should you make that 70% ethanol with demineralized water or with tap water? My colleague argues with demi water because this water is “purer” as far as bacteria are concerned. In my opinion this is not correct: demineralised water is not sterile water. I think there is another reason why you should use demineralized water.
Or is there no real reason why you should use demineralised water to make 70% ethanol solution?
Answer
Hi Jan,
with us we use demineralised water for 70% EtOH solutions. The reason is not so much that demineralized water is (more) sterile, because since the solution is used for disinfection, the ethanol in the 70% solution will automatically kill possible contaminations from the tap or demineralized water.
The reason is rather that demineralised water, in contrast to tap water, contains few dissolved substances. When, for example, we treat the work surface or glassware with that 70% solution, we are sure that no limescale (certainly in Leuven, for example!) or other salt spots remain.
A certain reason is probably also habit: we like to use demineralized water because it is simply purer than tap water.
I don’t think you need to look anymore.
Regards,
Benjamin
Answered by
Dr. Benjamien Moeyaert
Biochemistry, biophysics, spectroscopy, microscopy, neuroscience, virology, gene therapy
Old Market 13 3000 Leuven
https://www.kuleuven.be/
.