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Article: Solid titration of octacalcium phosphate

TitleSolid titration of octacalcium phosphate
Authors
KeywordsHydroxyapatite
Octacalcium phosphate
Solid titration
Solubility
Issue Date2009
PublisherS Karger AG. The Journal's web site is located at http://www.karger.com/CRE
Citation
Caries Research, 2009, v. 43 n. 4, p. 322-330 How to Cite?
AbstractOctacalcium phosphate (OCP) is of considerable importance as a precursor in the formation of dental enamel and an intermediate phase in the precipitation of hydroxyapatite (HAp) in bone. However, agreement is poor on the solubility product (pKsp), possibly due to the formation of the more stable phase HAp. The system was investigated using solid titration, which has shown reliability in work on HAp and related fluoride minerals, with OCP in 100 mM KCl at 37.0 ± 0.1°C. The constitution of the end point precipitate was determined by X-ray diffraction and selected-electron area diffraction; the particle morphology and elements present were examined by high-resolution field emission scanning, transmission electron microscopy and energy-dispersive X-ray analysis. The titration curve for OCP was found for pH ∼3.4-7.4. The precipitate was HAp at pH 3.6 and 4.5; no residual OCP or other phase was detected. Dicalcium phosphate dihydrate (DCPD) was then found to form at pH 3.6 on further addition of OCP titrant after equilibrium had been achieved, possibly due to easier nucleation at lower pH. However, markedly crystalline HAp was formed in equilibrium for OCP titration with HAp seeding, verifying HAp as the more stable phase. A solubility isotherm for OCP was not obtained as HAp appears to be less soluble in the pH range studied. This adds weight to the view that HAp may be the most stable phase of all calcium phosphates, with further doubt being cast on DCPD being the most stable phase below pH 4.2. However, metastable DCPD may form in an Ostwald succession, depending on supersaturation and nucleation conditions. Copyright © 2009 S. Karger AG, Basel.
Persistent Identifierhttp://hdl.handle.net/10722/170146
ISSN
2015 Impact Factor: 2.278
2015 SCImago Journal Rankings: 1.014
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorPan, HBen_HK
dc.contributor.authorDarvell, BWen_HK
dc.date.accessioned2012-10-30T06:05:36Z-
dc.date.available2012-10-30T06:05:36Z-
dc.date.issued2009en_HK
dc.identifier.citationCaries Research, 2009, v. 43 n. 4, p. 322-330en_HK
dc.identifier.issn0008-6568en_HK
dc.identifier.urihttp://hdl.handle.net/10722/170146-
dc.description.abstractOctacalcium phosphate (OCP) is of considerable importance as a precursor in the formation of dental enamel and an intermediate phase in the precipitation of hydroxyapatite (HAp) in bone. However, agreement is poor on the solubility product (pKsp), possibly due to the formation of the more stable phase HAp. The system was investigated using solid titration, which has shown reliability in work on HAp and related fluoride minerals, with OCP in 100 mM KCl at 37.0 ± 0.1°C. The constitution of the end point precipitate was determined by X-ray diffraction and selected-electron area diffraction; the particle morphology and elements present were examined by high-resolution field emission scanning, transmission electron microscopy and energy-dispersive X-ray analysis. The titration curve for OCP was found for pH ∼3.4-7.4. The precipitate was HAp at pH 3.6 and 4.5; no residual OCP or other phase was detected. Dicalcium phosphate dihydrate (DCPD) was then found to form at pH 3.6 on further addition of OCP titrant after equilibrium had been achieved, possibly due to easier nucleation at lower pH. However, markedly crystalline HAp was formed in equilibrium for OCP titration with HAp seeding, verifying HAp as the more stable phase. A solubility isotherm for OCP was not obtained as HAp appears to be less soluble in the pH range studied. This adds weight to the view that HAp may be the most stable phase of all calcium phosphates, with further doubt being cast on DCPD being the most stable phase below pH 4.2. However, metastable DCPD may form in an Ostwald succession, depending on supersaturation and nucleation conditions. Copyright © 2009 S. Karger AG, Basel.en_HK
dc.languageengen_US
dc.publisherS Karger AG. The Journal's web site is located at http://www.karger.com/CREen_HK
dc.relation.ispartofCaries Researchen_HK
dc.rightsCaries Research. Copyright © S Karger AG.-
dc.subjectHydroxyapatiteen_HK
dc.subjectOctacalcium phosphateen_HK
dc.subjectSolid titrationen_HK
dc.subjectSolubilityen_HK
dc.subject.meshBone Substitutes - Chemistryen_US
dc.subject.meshCalcium Phosphates - Chemistryen_US
dc.subject.meshCrystallographyen_US
dc.subject.meshHydroxyapatites - Chemistryen_US
dc.subject.meshPhase Transitionen_US
dc.subject.meshSolubilityen_US
dc.subject.meshTitrimetryen_US
dc.subject.meshX-Ray Diffractionen_US
dc.titleSolid titration of octacalcium phosphateen_HK
dc.typeArticleen_HK
dc.identifier.emailPan, HB: haobo@hku.hken_HK
dc.identifier.emailDarvell, BW: b.w.darvell@hku.hken_HK
dc.identifier.authorityPan, HB=rp01564en_HK
dc.identifier.authorityDarvell, BW=rp00007en_HK
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1159/000226231en_HK
dc.identifier.pmid19556792-
dc.identifier.scopuseid_2-s2.0-67649203115en_HK
dc.identifier.hkuros163520-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-67649203115&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume43en_HK
dc.identifier.issue4en_HK
dc.identifier.spage322en_HK
dc.identifier.epage330en_HK
dc.identifier.isiWOS:000268106900012-
dc.publisher.placeSwitzerlanden_HK
dc.identifier.scopusauthoridPan, HB=7403295092en_HK
dc.identifier.scopusauthoridDarvell, BW=7005953926en_HK

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