Tricalcium phosphate

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Tricalcium phosphate
Tricalcium phosphate.svg
Names
IUPAC name
Tricalcium bis(phosphate)
Other names
Tribasic calcium phosphate
Identifiers
ATC code A12AA01
7758-87-4 YesY
ChEBI CHEBI:9679 YesY
ChemSpider 22864 YesY
Jmol-3D images Image
PubChem 516943
UNII K4C08XP666 YesY
Properties
Ca3O8P2
Molar mass 310.18 g·mol−1
Appearance White amorphous powder
Density 3.14 g/cm3
Melting point Liquifies under high pressure at 1670 K (1391 °C)
0.002 g/100 g
Thermochemistry
-4126 kcal/mol (α-form)[1]
Hazards
EU Index Not listed
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
Related compounds
Other anions
Calcium pyrophosphate
Other cations
Trimagnesium phosphate
Trisodium phosphate
Tripotassium phosphate
Related compounds
Monocalcium phosphate
Dicalcium phosphate
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Tricalcium phosphate (sometimes abbreviated TCP) is a calcium salt of phosphoric acid with the chemical formula Ca3(PO4)2. It is also known as tribasic calcium phosphate and bone phosphate of lime (BPL). Calcium phosphate is one of the main combustion products of bone (see bone ash). Calcium phosphate is also commonly derived from inorganic sources such as mineral rock.[2]

It has three crystalline polymorphs α, α' and β. The α and α' states are formed at high temperatures. As rock, it is found in Whitlockite.

Nomenclature[edit]

Main article: Calcium phosphate

Calcium phosphate refers to minerals containing calcium ions (Ca2+) together with orthophosphates (PO43−), metaphosphates or pyrophosphates (P2O74−) and occasionally hydrogen or hydroxide ions. Especially, the common mineral apatite has formula Ca5(PO4)3X, where X is F, Cl, OH, or a mixture; it is hydroxyapatite if the extra ion is mainly hydroxide. Much of the "tricalcium phosphate" on the market is actually powdered hydroxyapatite.

Preparation of pure Ca3(PO4)2[edit]

It is generally believed that tricalcium phosphate cannot be precipitated directly from aqueous solution. Typically a double decomposition reaction involving a soluble phosphate and calcium salts (e.g. (NH4)2HPO4 + Ca(NO3)2)[3] is performed under carefully controlled pH conditions. The precipitate will either be "amorphous tricalcium phosphate", ATCP, or calcium deficient hydroxypatite, CDHA, Ca9(HPO4)(PO4)5(OH), (note CDHA is sometimes termed apatitic calcium triphosphate).[3][4][5] Crystalline tricalcium phosphate can be obtained by calcining the precipitate. β-Ca3(PO4)2 is generally formed, higher temperatures are required to produce α-Ca3(PO4)2.

An alternative to a wet procedure is to heat a dry mixture of a calcium phosphate and calcium carbonate which has an overall Ca/P ratio of 3:2, for example:[4]

CaCO3 + Ca2P2O7 → Ca3(PO4)2 + CO2

Crystal structure of β-, α- and α'- Ca3(PO4)2 polymorphs[edit]

Tricalcium phosphate has three recognised polymorphs, the rhombohedral β- form, and two high temperature forms, monoclinic α- and hexagonal α'-. β-tricalcium phosphate has a crystallographic density of 3.066 g cm−3 while the high temperature forms are less dense, α-tricalcium phosphate has a density of 2.866 g cm−3 and α'-tricalcium phosphate has a density of 2.702 g cm−3 They all have complex structures and have been described as containing "columns" of cations and anions. The β-form has two types of columns, each containing calcium and phosphate ions. The high temperature forms each have two types of columns, one containing only calcium ions and the other both calcium and phosphate.[6]

There are differences in chemical and biological properties between the beta and alpha forms, the alpha form is more soluble and biodegradeable. Both forms are avalable commercially and are present in formulations used in medical and dental applications.[6]

Natural occurrence[edit]

Tricalcium phosphate occurs naturally in several forms, including:

  • as a rock in Morocco, Israel, Philippines, Egypt, and Kola (Russia) and in smaller quantities in some other countries. The natural form is not completely pure, and there are some other components like sand and lime which can change the composition. In terms of P2O5, most calcium phosphate rocks have a content of 30% to 40% P2O5 in weight.
  • in the skeletons and teeth of vertebrate animals
  • in milk.

Biphasic tricalcium phosphate, BCP[edit]

Biphasic tricalcium phosphate, BCP, was originally reported as tricalcium phosphate but X-Ray diffraction techniques showed that the material was an intimate mixture of two phases, hydroxyapatite, HA, and β-tricalcium phosphate.[7] It is a ceramic.[8] Preparation involves the sintering causing the irreversible decomposition of calcium deficient apatites[4] alternatively termed non-stoichiometric apatites or basic calcium phosphate,[9] an example is:[10]

Ca10-δ(PO4)6-δ(HPO4)δ(OH)2-δ → (1-δ)Ca10(PO4)6(OH)2 + 3δCa3(PO4)2

β-TCP can contain impurities, for example calcium pyrophosphate, CaP2O7 and apatite. β-TCP is bioresorbable. The biodegradation of BCP involves faster dissolution of the β-TCP phase followed by elimination of HA crystals. β-TCP does not dissolve in body fluids at physiological pH levels, dissolution requires cell activity producing acidic pH.[4]

Uses[edit]

Tricalcium phosphate is used in powdered spices as an anticaking agent. It is also found in baby powder.

Calcium phosphate is an important raw material for the production of phosphoric acid and fertilizers, for example in the Odda process. Phosphate ore quality and quantity is often specified as percent BPL (bone phosphate of lime), where 1% BPL is equivalent to 0.458% P2O5.[11]

Calcium phosphate is also a raising agent (food additive) E341. As a mineral salt found in rocks and bones, it is used in cheese products.

It is also used as a nutritional supplement[12] and occurs naturally in cow milk[citation needed], although the most common and economical forms for supplementation are calcium carbonate (which should be taken with food) and calcium citrate (which can be taken without food).[13] There is some debate about the different bioavailabilities of the different calcium salts.

It is commonly used in porcelain and dental powders, and medically as an antacid or calcium supplement, although calcium carbonate is more common in this regard.

It can be used as a tissue replacement for repairing bony defects when autogenous bone graft is not feasible or possible.[14][15][16] It may be used alone or in combination with a biodegradable, resorbable polymer such as polyglycolic acid.[17] It may also be combined with autologous materials for a bone graft.[18][19]

Porous beta-Tricalcium phosphate scaffolds are employed as drug carrier systems for local drug delivery in bone.[20]

Another practical application of the compound is its use in gene transfection. The calcium ions can make a cell competent to allow exogenous genes to enter the cell by diffusion. A heat shock afterwards then invokes the cell to repair itself. This is a quick and easy method for transfection, albeit a rather inefficient one.

Calcium triphosphate is used to remove fluoride from water in water filtration systems.[21]

References[edit]

  1. ^ Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A21. ISBN 0-618-94690-X. 
  2. ^ Yacoubou, Jeanne, MS. Vegetarian Journal's Guide To Food Ingredients "Guide to Food Ingredients". The Vegetarian Resource Group, n.d. Web. 14 Sept. 2012.
  3. ^ a b Destainville, A., Champion, E., Bernache-Assollant, D., Laborde, E. (2003). "Synthesis, characterization and thermal behavior of apatitic tricalcium phosphate". Materials Chemistry and Physics 80 (1): 269–277. doi:10.1016/S0254-0584(02)00466-2. ISSN 1742-7061.   – via ScienceDirect (Subscription may be required or content may be available in libraries.)
  4. ^ a b c d Rey, C.; Combes, C.; Drouet, C.; Grossin, D. (2011). "1.111 - Bioactive Ceramics: Physical Chemistry". In Ducheyne, Paul. Comprehensive Biomaterials 1. Elsevier. pp. 187–281. doi:10.1016/B978-0-08-055294-1.00178-1. ISBN 978-0-08-055294-1.   – via ScienceDirect (Subscription may be required or content may be available in libraries.)
  5. ^ Dorozhkin, Sergey V. (December 2012). "Amorphous calcium (ortho)phosphates". Acta Biomaterialia 6 (12): 4457–4475. doi:10.1016/j.actbio.2010.06.031. ISSN 1742-7061.   – via ScienceDirect (Subscription may be required or content may be available in libraries.)
  6. ^ a b Carrodeguas, R.G.; De Aza, S. (2011). "α-Tricalcium phosphate: Synthesis, properties and biomedical applications". Acta Biomaterialia 7 (10): 3536–3546. doi:10.1016/j.actbio.2011.06.019. ISSN 1742-7061.   – via ScienceDirect (Subscription may be required or content may be available in libraries.)
  7. ^ Daculsi, G.; Legeros, R. (2008). "17 - Tricalcium phosphate/hydroxyapatite biphasic ceramics". In Kokubo, Tadashi. Bioceramics and their Clinical Applications. Woodhead Publishing. pp. 395–423. doi:10.1533/9781845694227.2.395. ISBN 978-1-84569-204-9.   – via ScienceDirect (Subscription may be required or content may be available in libraries.)
  8. ^ Salinas, Antonio J.; Vallet-Regi, Maria (2013). "Bioactive ceramics: from bone grafts to tissue engineering". RSC Advances (Royal Society of Chemistry) 3 (28): 11116–11131. doi:10.1039/C3RA00166K. Retrieved 15 February 2015. (subscription required (help)). 
  9. ^ Elliott, J.C. (1994). "3 - Hydroxyapatite and Nonstoichiometric Apatites". Studies in Inorganic Chemistry 18. Elsevier. pp. 111–189. doi:10.1016/B978-0-444-81582-8.50008-0. ISSN 0169-3158. Retrieved 15 February 2015.   – via ScienceDirect (Subscription may be required or content may be available in libraries.)
  10. ^ Vallet-Regí, M.;Rodríguez-Lorenzo, L.M. (November 1997). "Synthesis and characterisation of calcium deficient apatite". Solid State Ionics. 101–103, Part 2: 1279–1285. doi:10.1016/S0167-2738(97)00213-0.   – via ScienceDirect (Subscription may be required or content may be available in libraries.)
  11. ^ Ober, JA, Phosphate Rock: U.S. Geological Survey Mineral Information 
  12. ^ Bonjour JP, Carrie AL, Ferrari S, Clavien H, Slosman D, Theintz G, Rizzoli R (March 1997). "Calcium-enriched foods and bone mass growth in prepubertal girls: a randomized, double-blind, placebo-controlled trial". J. Clin. Invest. 99 (6): 1287–94. doi:10.1172/JCI119287. PMC 507944. PMID 9077538. 
  13. ^ Straub DA (June 2007). "Calcium supplementation in clinical practice: a review of forms, doses, and indications". Nutr Clin Pract 22 (3): 286–96. doi:10.1177/0115426507022003286. PMID 17507729. 
  14. ^ Paderni S, Terzi S, Amendola L (September 2009). "Major bone defect treatment with an osteoconductive bone substitute". Musculoskelet Surg 93 (2): 89–96. doi:10.1007/s12306-009-0028-0. PMID 19711008. 
  15. ^ Moore DC, Chapman MW, Manske D (1987). "The evaluation of a biphasic calcium phosphate ceramic for use in grafting long-bone diaphyseal defects". Journal of Orthopaedic Research 5 (3): 356–65. doi:10.1002/jor.1100050307. PMID 3040949. 
  16. ^ Lange TA, Zerwekh JE, Peek RD, Mooney V, Harrison BH (1986). "Granular tricalcium phosphate in large cancellous defects". Annals of Clinical and Laboratory Science 16 (6): 467–72. PMID 3541772. 
  17. ^ Cao H, Kuboyama N (September 2009). "A biodegradable porous composite scaffold of PGA/beta-TCP for bone tissue engineering". Bone 46 (2): 386–95. doi:10.1016/j.bone.2009.09.031. PMID 19800045. 
  18. ^ Erbe EM, Marx JG, Clineff TD, Bellincampi LD (October 2001). "Potential of an ultraporous beta-tricalcium phosphate synthetic cancellous bone void filler and bone marrow aspirate composite graft". European Spine Journal : Official Publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society. 10 Suppl 2: S141–6. doi:10.1007/s005860100287. PMID 11716011. 
  19. ^ Bansal S, Chauhan V, Sharma S, Maheshwari R, Juyal A, Raghuvanshi S (July 2009). "Evaluation of hydroxyapatite and beta-tricalcium phosphate mixed with bone marrow aspirate as a bone graft substitute for posterolateral spinal fusion". Indian Journal of Orthopaedics 43 (3): 234–9. doi:10.4103/0019-5413.49387. PMC 2762171. PMID 19838344. 
  20. ^ Kundu, B; Lemos A; Soundrapandian C; Sen PS; Datta S; Ferreira JMF; Basu D (2010). "Development of porous HAp and β-TCP scaffolds by starch consolidation with foaming method and drug-chitosan bilayered scaffold based drug delivery system". J Mater. Sci. Mater. Med. 21 (11): 2955–69. doi:10.1007/s10856-010-4127-0. PMID 20644982. 
  21. ^ He, GL, Assessment of Fluoride Removal From Drinking Water by Calcium Phosphate Systems