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. 2004 Dec 1;109(6):553-68.
doi: 10.6028/jres.109.042. Print 2004 Nov-Dec.

Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material

Milenko Markovic  1 , Bruce O Fowler  2 , Ming S Tung  1
Affiliations

Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material

Milenko Markovic et al. J Res Natl Inst Stand Technol. .

Abstract

Numerous biological and chemical studies involve the use of calcium hydroxyapatite (HA), Ca10(PO4)6(OH)2. In this study detailed physicochemical characterization of HA, prepared from an aqueous solution, was carried out employing different methods and techniques: chemical and thermal analyses, x-ray diffraction, infrared and Raman spectroscopies, scanning and transmission microscopies, and Brunauer, Emmett, and Teller (BET) surface-area method. The contents of calcium (Ca(2+)), phosphate (PO4 (3-)), hydroxide (OH(-)), hydrogenphosphate (HPO4 (2-)), water (H2O), carbonate (CO3 (2-)), and trace constituents, the Ca/P molar ratio, crystal size and morphology, surface area, unit-cell parameters, crystallinity, and solubility of this HA were determined. This highly pure, homogeneous, and highly crystalline HA is certified as a National Institute of Standards and Technology (NIST) standard reference material, SRM 2910.

Keywords: Raman; chemical analysis; crystal size; crystallinity; hydroxyapatite; infrared; morphology; preparation; solubility; surface area; thermal analysis; unit-cell parameters; x-ray diffraction.

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Figures

Fig. 1
Fig. 1
TG-curve for HA-SRM in the temperature range from 30 °C to 900 °C in a nitrogen atmosphere. The left ordinate denotes the mass fraction and the right ordinate gives the corresponding calculated number of water layers progressively removed from the HA-SRM surface.
Fig. 2
Fig. 2
Transmission electron micrograph (top) and scanning electron micrograph (bottom) of the HA-SRM crystals. Both micro-graphs have the same magnification and the bar length in the top micrograph is 0.5 μm.
Fig. 3
Fig. 3
Infrared percent transmittance spectra of HA-SRM from concentrations of 0.8 mg and 4.0 mg of HA-SRM/400 mg of KBr in the 4000 cm−1 to 300 cm−1 region. BL denotes the KBr pellet baseline.
Fig. 4
Fig. 4
Infrared absorbance spectrum of the ν3 PO4 mode of HA-SRM (dashed line) and second derivative of the absorbance spectrum (solid line). The second derivative spectrum ordinate scale, not shown, is arbitrary. The second derivative spectrum was adjusted to full ordinate range and the minima denoted by numbers identify band positions in the absorbance spectrum.
Fig. 5
Fig. 5
Infrared absorbance spectrum of the ν4 PO4 mode of HA-SRM (dashed line) and second derivative of the absorbance spectrum (solid line). The absorbance band at 633 cm−1 and second derivative band at 633 cm−1 derive from the OH− librational mode. The description of the second derivative spectrum is the same as that given in Fig. 4.
Fig. 6
Fig. 6
Raman spectra of HA-SRM from 4000 cm−1 to 50 cm−1 recorded at relative intensities of 1 and 10 below 1200 cm−1 and 3.3 above 1200 cm−1. BL denotes the baseline.
Fig. 7
Fig. 7
X-ray diffraction pattern of HA-SRM in the 2θ range from 3° to 70°.
See this image and copyright information in PMC

References

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    1. Markovic M, Fowler BO, Tung MS, Lagergren ES. Composition and Solubility Product of a Synthetic Calcium Hydroxyapatite. Chemical and Thermal Determination of Ca/P Ratio and Statistical Analysis of Chemical and Solubility Data. In: Amjad Z, editor. Mineral and Scale Formation, Proc of ACS Symposium. Plenum; New York: 1995. pp. 271–282.
    1. Certificate of Analysis, Standard Reference Material 2910. National Institute of Standards and Technology; Gaithersburg, MD, USA: 1997.

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