Calcium phosphate
{{short description|Chemical compound}}
{{For|the function of calcium phosphate in organisms|Calcium metabolism}}
{{Chembox
| ImageFile = Hydroxylapatite-338779.jpg
| ImageCaption = Hydroxyapatite crystal
| Section1 = {{Chembox Identifiers
| CASNo = 7758-87-4
| EC_number = 233-283-6
| PubChem = 24456
| UNII = K4C08XP666
| StdInChIKey = QORWJWZARLRLPR-UHFFFAOYSA-H
}}
| Section2 = {{Chembox Properties
| Formula = Ca3(PO4)2
| MolarMass = 310.18 g/mol
| Appearance = White Solid
| Odor = Odorless
| Density = 3.14 g/cu cm{{cite web | url=https://pubchem.ncbi.nlm.nih.gov/compound/Calcium-phosphate | title=Calcium Phosphate }}
| MeltingPtC = 1670
| Solubility = Practically insoluble with water
| Solvent2 = Ethanol
| Solubility2 = Insoluble with ethanol (also acetic acid)
}}
| Section3 = {{Chembox Hazards
| GHSPictograms = {{GHS07}}
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|315|319|335}}
| PPhrases = {{P-phrases|101|102|103|261|264|271|280|270|302+352|304+340|305+351+338}}
| NFPA-H = 2
| NFPA-F = 0
| NFPA-R = 1
| NFPA-S =
| FlashPt = Non-flammable
| ExternalSDS = [https://beta-static.fishersci.com/content/dam/fishersci/en_US/documents/programs/education/regulatory-documents/sds/chemicals/chemicals-c/S25229.pdf fishersci.com]
}}
}}
The term calcium phosphate refers to a family of materials and minerals containing calcium ions (Ca2+) together with inorganic phosphate anions. Some so-called calcium phosphates contain oxide and hydroxide as well. Calcium phosphates are white solids of nutritional value{{cite book|author1=Klaus Schrödter|author2=Gerhard Bettermann|author3=Thomas Staffel|author4=Friedrich Wahl|author5=Thomas Klein|author6=Thomas Hofmann|title=Ullmann's Encyclopedia of Industrial Chemistry|chapter=Phosphoric Acid and Phosphates|series=Ullmann’s Encyclopedia of Industrial Chemistry|year=2008|publisher=Wiley-VCH|place=Weinheim|doi=10.1002/14356007.a19_465.pub3|isbn=978-3527306732|s2cid=94458523 }} and are found in many living organisms, e.g., bone mineral and tooth enamel.{{Cite web|date=2015-07-15|title=What Substances Make Up Your Teeth? – Affordable Dental Care|url=https://www.towncaredental.com/blog/what-substances-make-up-your-teeth/|access-date=2021-01-29|website=www.towncaredental.com|language=en-us}} In milk, it exists in a colloidal form in micelles bound to casein protein with magnesium, zinc, and citrate–collectively referred to as colloidal calcium phosphate (CCP).{{cite book|title=Brined cheeses - The Society of Dairy Technology (SDT)|publisher=Wiley-Blackwell|year=2006|isbn=978-1-4051-2460-7|editor=A. Y. Tamime}} Various calcium phosphate minerals, which often are not white owing to impurities, are used in the production of phosphoric acid and fertilizers. Overuse of certain forms of calcium phosphate can lead to nutrient-containing surface runoff and subsequent adverse effects upon receiving waters such as algal blooms and eutrophication (over-enrichment with nutrients and minerals).{{Cite journal |last1=Xiao |first1=Zhengyang |last2=Tan |first2=Albern X. |last3=Xu |first3=Vincent |last4=Jun |first4=Young-Shin |last5=Tang |first5=Yinjie J. |date=2022 |title=Mineral-hydrogel composites for mitigating harmful algal bloom and supplying phosphorous [sic] for photo-biorefineries |journal=Science of the Total Environment |language=en |volume=847 |pages=157533 |doi=10.1016/j.scitotenv.2022.157533 |pmc=9755271 |pmid=35878849|bibcode=2022ScTEn.84757533X }}
Orthophosphates, di- and monohydrogen phosphates
These materials contain Ca2+ combined with {{chem|PO|4|3−}}, {{chem|HPO|4|2−}}, or {{chem|H|2|PO|4|−}}:
- Monocalcium phosphate, E341 (CAS# 7758-23-8 for anhydrous; CAS#10031-30-8 for monohydrate: Ca(H2PO4)2 and Ca(H2PO4)2(H2O)
- Dicalcium phosphate (dibasic calcium phosphate), E341(ii) (CAS# 7757-93-9): CaHPO4 (mineral: monetite), dihydrate CaHPO4(H2O)2 (mineral: brushite) and monohydrate CaHPO4(H2O)
- Tricalcium phosphate (tribasic calcium phosphate or tricalcic phosphate, sometimes referred to as calcium phosphate or calcium orthophosphate, whitlockite), E341(iii) (CAS#7758-87-4): Ca3(PO4)2
- Octacalcium phosphate (CAS# 13767-12-9): Ca8H2(PO4)6·5H2O
- Amorphous calcium phosphate is a glassy precipitate of variable composition that may be present in biological systems.
Di- and polyphosphates
These materials contain Ca2+ combined with the polyphosphates, such as pyrophosphate and triphosphate {{chem|P|3|O|10|5−}}:
- Dicalcium diphosphate (CAS#7790-76-3]: Ca2P2O7
- Calcium triphosphate (CAS# 26158-70-3): Ca5(P3O10)2
Hydroxy- and oxo-phosphates
These materials contain other anions in addition to phosphate:
- Hydroxyapatite Ca5(PO4)3(OH)
- Apatite Ca10(PO4)6(OH,F,Cl,Br)2
- Tetracalcium phosphate (CAS#1306-01-0): Ca4(PO4)2O
Culinary use
Calcium phosphate was approved by the FDA{{cite web|url=https://www.fda.gov/news-events/press-announcements/fda-approves-three-food-colors-natural-sources|archive-url=https://web.archive.org/web/20250509155205/https://www.fda.gov/news-events/press-announcements/fda-approves-three-food-colors-natural-sources|url-status=dead|archive-date=May 9, 2025|title=FDA Approves Three Food Colors from Natural Sources|publisher=FDA|lang=en}} in the USA for use as a white food coloring because of a 2023 petition from Innophos Inc. of Cranbury, New Jersey. [https://apnews.com/article/fda-food-dyes-natural-color-additives-897923a5969b636e0eee848982906014]
Clinical significance
Calcium phosphate stones account for approximately 15% of kidney stone disease. Calcium phosphate stones tend to grow in alkaline urine, especially when Proteus bacteria are present. It is the most common type in pregnant women.{{cite journal| author=Frassetto L, Kohlstadt I| title=Treatment and prevention of kidney stones: an update. | journal=Am Fam Physician | year= 2011 | volume= 84 | issue= 11 | pages= 1234–42 | pmid=22150656 | doi= | pmc= | url=https://pubmed.ncbi.nlm.nih.gov/22150656 }}
Calcium phosphate is the usual constitution of microcalcifications of the breast, particularly dystrophic calcifications. Microcalcifications as can be seen on mammography can be an early sign of breast cancer. Based on morphology, it is possible to classify by radiography how likely microcalcifications are to indicate cancer.{{cite journal |last1=Nalawade |first1=Yojana V |title=Evaluation of breast calcifications |journal=The Indian Journal of Radiology & Imaging |date=November 2009 |volume=19 |issue=4 |pages=282–286 |doi=10.4103/0971-3026.57208 |pmid=19881103 |issn=0971-3026|pmc=2797739 |doi-access=free }}
File:Urine crystals comparison.png|Urine crystals comparison, with calcium phosphate crystal depicted at top center.
File:Histopathology of dystrophic microcalcifications in ductal carcinoma in situ.jpg|Histopathology of dystrophic calcium phosphate microcalcifications in ductal carcinoma in situ (DCIS) of the breast, H&E stain.
References
{{Reflist}}
{{Calcium compounds}}
{{Phosphates}}
{{DEFAULTSORT:Calcium Phosphate}}