Hi, what pH do you need exactly and what experiments do you want to record? Sodium acetate is good starting point.

To add on to my question, pH will be 2.5. And also the buffer in which my protein exist (after dialysis)is 20mM phosphate buffer, 100mM NaCl, 0.01% Sodium azide and 2mM EDTA.

Can the same buffer act as NMR solvent?

if you mean phosphate...well, it will not be really suitable at pH 2.5, since phosphate is used at range 6.0-8.0. In your case, maybe citric acid is a good option. https://www.sigmaaldrich.com/life-science/core-bioreagents/biological-buffers/learning-center/buffer-reference-center.html

Really thank you. It is very helpful.