[Histonet] re:water question

Matthew Close matthewtclose <@t> gmail.com
Mon Mar 23 11:55:03 CDT 2009

I think that distilled water starts out at a ph of around 6-6.5, but usually
DI water is closer to 7.  Over time, both will drop in pH unless you buy
specialized housing for the DI water.  Since many people doing IHC at my
university are using RO water, which has a pH similar to what the pH of the
tap source, I would say you are probably okay going with the distilled
water.  My word of caution is to check the level of air in your housing tank
and never let it drop below half.  Typically, the more air in the tank, the
more CO2 going into the water which will gradually lower the pH down to
5.1-5.5 territory.  Also, if you have the option to chose between using a
glass carboy and a plastic one to store water, always go with the glass.
While all of this has never been a real problem for me in terms of
analyzable results, I often wonder if it has anything to do with why,
sometimes, identical staining procedures on identially fixed tissues will
stain notably different.

Matt Close
Department of Biological Sciences
Lehigh University

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