Measuring pH in 95% DMSO solutions?

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

jsp at wrote in message news:<20021030163433.3406.qmail at>...
> 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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