Calcium phosphate explained

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^[1] and are found in many living organisms, e.g., bone mineral and tooth enamel.^[2] 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).^[3] Various calcium phosphate minerals 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).^[4]

Orthophosphates, di- and monohydrogen phosphates

These materials contain Ca²⁺ combined with,, or :

• 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, 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 and triphosphate :

• 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

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.^[5]

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.^[6]

Notes and References

1. Book: Klaus Schrödter. Gerhard Bettermann. Thomas Staffel. Friedrich Wahl. Thomas Klein. Thomas Hofmann. Ullmann's Encyclopedia of Industrial Chemistry. Phosphoric Acid and Phosphates. Ullmann’s Encyclopedia of Industrial Chemistry. 2008. Wiley-VCH. Weinheim. 10.1002/14356007.a19_465.pub3. 978-3527306732. 94458523 .
2. Web site: 2015-07-15. What Substances Make Up Your Teeth? – Affordable Dental Care. 2021-01-29. www.towncaredental.com. en-us.
3. Book: Brined cheeses - The Society of Dairy Technology (SDT). Wiley-Blackwell. 2006. 978-1-4051-2460-7. A. Y. Tamime.
4. Xiao . Zhengyang . Tan . Albern X. . Xu . Vincent . Jun . Young-Shin . Tang . Yinjie J. . 2022 . Mineral-hydrogel composites for mitigating harmful algal bloom and supplying phosphorous for photo-biorefineries . Science of the Total Environment . en . 847 . 157533 . 10.1016/j.scitotenv.2022.157533 . 9755271 . 35878849.
5. Frassetto L, Kohlstadt I. Treatment and prevention of kidney stones: an update. . Am Fam Physician . 2011 . 84 . 11 . 1234–42 . 22150656 .
6. Nalawade . Yojana V . Evaluation of breast calcifications . The Indian Journal of Radiology & Imaging . November 2009 . 19 . 4 . 282–286 . 10.4103/0971-3026.57208 . 19881103 . 0971-3026. 2797739 . free .