I prepared a fresh PBS stock solution (10X) and after few days in the fridge (4°C) I observe some crystallisation on the bottom... which disappears when i heat up the whole solution again...
Is that normal? For information, i mixed the following (in 1L of milliQ water):
- 80 g NaCl
- 2g KCl
- 18.05 g (Na2,HPO4)(2H2O)
-2.4 g KH2PO4
and then i adjusted the pH at 7.4 with HCl.