Laboratory Investigations

Calcified Tissue International

, Volume 49, Issue 6, pp 383-388

First online:

Resolution-enhanced fourier transform infrared spectroscopy study of the environment of phosphate ion in the early deposits of a solid phase of calcium phosphate in bone and enamel and their evolution with age: 2. Investigations in thev 3 PO4 domain

  • C. ReyAffiliated withLaboratoire de Physico-chimie des Solides, C.N.R.S. (UA 445)
  • , M. ShimizuAffiliated withSchool of Dental Medicine, Tsurumi University
  • , B. CollinsAffiliated withDepartment of Chemistry, National Institute of Environmental Health Science
  • , M. J. GlimcherAffiliated withLabratory for the Study of Skeletal Disorders and Rehabilitation, The Children's Hospital, Harvard Medical School

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Resolution-enhanced Fourier Transform Infrared (FTIR) spectra of early mineral deposits in enamel and bone show bands at 1020, 1100, 1110, 1125, and 1145 cm−1 in thev 3PO4 domain which do not belong to well crystallized stoichiometric hydroxyapatite. Bands at 1020 and 1100 cm−1 have been shown to occur in nonstoichiometric apatites containing HPO 4 2− ions. Though the bands at 1110 and 1125 cm−1 have not been found in any well crystallized apatite, they are present in newly precipitated apatite. These latter bands disappear progressively during maturation in biological as well as synthetic samples, and partial dissolution of synthetic apatites shows that they belong to species that exhibit an inhomogeneous distribution in the mineral, and that are the first to be solubilized. Comparison of the FTIR spectra of biological apatites with those of synthetic, nonapatitic-containing phosphate minerals shows that the presence of these bands does not arise from nonapatitic, well-defined phases; they are due to the local environment of phosphate ions which may possibly be loosely related or perhaps unrelated to the phosphate groups present in the well-crystallized nonapatitic calcium phosphates. Resolution-enhanced FTIR affords a very precise characterization of the mineral phases which may be very useful in characterizing pathological deposits of Ca−P mineral phases.

Key words

Infrared spectroscopy Bone Enamel Carbonate Phosphate