Oligo stability in water at -20 C

Peter pxpst2 at unixs.cis.pitt.edu
Wed Aug 12 14:01:56 EST 1998


In article <19980812151539.19492.rocketmail at send102.yahoomail.com>,
rjdudley at yahoo.com wrote:
 
> The definition is true; however, Milli-Q is not "pure by definition"
> water.  There are dissolved gasses (e.g., CO2, N2, O2).  CO2 is of
> special importance, since it does play a role in buffering water (and
> your blood) with the carbonate-bicarbonate buffering system.  The mere
> act of retrieving water from the Milli-Q tap intorduces CO2. 
> Adidtionally, I don't think that Milli-Q (or other deionization
> systems) scrub protons; they are more geared for nitrates, sulfates,
> etc.

Not true.
Most Milli-Q systems have a .22um filter that is connected at point of
dispencing, therefore, disolved gasses are virtually non-exsistant.  Also
if your conductivity meter is working correctly and it reads >18MOhms then
it is safe to say you have no ions.  Because if you did have ions then you
would see a conductance of less than ~17 MOhms.
Also most Milli-Q systems have a cartirage that is called a "polishing
cartirage".  It is made up of activated carbon which will bind to
uncharged molecules.  It works by a priciple called "adsorption".  With
regard to carbon, all polar or species with lone pair electrons will
bind.  The only way for them to be released is by heating the carbon up.
The charged species that you mentioned will be removed by the initial
cartridges which are made with Strong cation and Anion resin.
If you allow your water to sit exposed to the atmossphere for any length
of time then some C02 would disolve into solution and a buffer may form.

Peter

-- 
"Don't you eat that yellow snow
            watch out where the Huskies go"    FZ

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