Measuring pH in 95% DMSO solutions?

Rene renevanwezel at hotmail.com
Thu Oct 31 12:46:30 EST 2002


jsp at bio.auc.dk wrote in message news:<20021030163433.3406.qmail at ww02.hostica.com>...
> Hi there,
> 
> I'm trying to make a 95% DMSO, 4.5% H2O, 0.5% CH2ClCOOH solution at pH 5, by adjusting pH with HCl.
> 
> Im using a standard pH-meter (Hamilton minitrode), but I can't seem to get stable readings due to the low water activity. If I clean the electrode and re-introduce it into the DMSO solution I get a completly different reading. Does anyone have a good suggestion how to accurately measure the pH?
> 

Get your water fraction at pH5 and then mix with DMSO. You could try
diluting your solution 10 fold to see whether your pH is still around
5 and not fluctuating.



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