I don't see any problems with freezing a buffer. It is inorganic salt - mix it well before use, maybe filtrate it. Remember about the change of density (don't freez full bottle).

Regards

G

Thank you Grzegorz!

To freeze or not freeze comes next but, we need to be certain about the word "freez" in your question. If you mean to drop the temp below zero so that it turns from liquid to solid, then it is better not to freeze. Particularly if the borate buffer is composed of sodium tetraborate decahydrate (Na₂B₄O₇·10H₂O) and boric acid. Although Na₂B₄O₇·10H₂O is soluble in water to about 38.1g/L, once this mass is exceeded gentle warming is required to dissolve it before preparing the buffer. Accordingly, freezing the buffer with the above composition will require constant warming once it is to be used which could potentially affect the concentration of the buffer due to the possible evaporation of the solvent in this case water. However, if the borate buffer consists of boric acid and NaOH it can be frozen.