In the context of calcium phosphate mineralization, P NMR is a useful probe for mineral phase analysis, allowing the understanding of subtle structural modifications induced by ionic substitutions or growth underconfinement, for instance. But before the study CaP mineralization process using the above described freeze-quench device, the behavior of pure phosphate solutions must be evaluated in these preparation conditions to check the correct cryofixation of the solutions and to get 31 P NMR reference spectra at -120 0 C since the low temperature can impact NMR chemical shifts.