I am working with polymer:salt aqueous two phase systems to purify a small organic chemical product. The distribution of the chemical depends on the pH of the solution, so I want to test different pH values and with different salts.
The first problem I have, is that the different salts (Potassium carbonate, Sodium sulfate, Potassium phosphate) will affect the pH due to their acidity/basicity. I thought I might formulate solutions with the desired pH values by mixing specific ratios of the acids and conjugate bases, but the desired pH values are sometimes far from the pKa values of the buffers (e.g. pH 10 in a potassium buffer). I am not sure if the Henderson Hasselbach equation can be used in such cases, and the predicted pH would still be off due to the high ionic strength (~1-2 M), beyond what the Debye Hückel theory can correct for.
Alternatively I thought I might just adjust the pH of the buffers with strong acid/base.
The second problem I have, is that I can't accurately measure the pH values of concentrated (~10-20% w/w) salt solutions with a standard glass electrode. I am considering using the specific salt as a filling solution in the electrode instead of KCl, or using a buffer with the salt for calibration. But I don't know how either approach will work in practice.
Any advice, input, or references would be welcomed!
You need special electrode for salt solutions which mostly used in marine sciences.
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