Phosphorus-31 spin-lattice NMR relaxation in bone apatite and its mineral standards

For T1ρP, both its magnitude and dependence on the CP contact time gave useful structural information. The dehydrated samples (HAc and BHA) had long T1ρP over 250 ms. Those, which contained water, either structural (BRU) or adsorbed on the crystal surface (HAh, CHA-B, and B1-B6), had shorter T1ρP below 120 ms. It was concluded that the effect of water on T1ρP is much more pronounced than on T1P. The interpretation has involved P-OH groups and adsorbed water, which cover the apatite crystal surface.