Slow MAS spinning (MAS = 2 kHz) was also used to record the SSB manifold after 1 minute of reaction (Figure ). Fitting the resulting CSA pattern with contributions from only HPO₄²⁻ and H₂PO4⁻ (where a 50/50 proportion is expected at pH 6.6 -see Figure ) cannot account for the full SSB signal intensity justifying the presence of an extra contribution in agreement with the presence of ACP. To further analyze these samples, advanced experiments such as two-dimensional (2D) 1 H-31 P or 31 P-31 P correlation NMR could provide valuable insights into the assignment of species present in the mixtures.