Calcium phosphate

Template:Short description Template:For Template:Chembox 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<ref name=Ullmann>Template:Cite book</ref> and are found in many living organisms, e.g., bone mineral and tooth enamel.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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).<ref>Template:Cite book</ref> 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).<ref>Template:Cite journal</ref>

Orthophosphates, di- and monohydrogen phosphates

These materials contain Ca²⁺ combined with Template:Chem, Template:Chem, or Template:Chem:

• 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|Template:Chem]] and triphosphate Template:Chem:

• 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<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> in the USA for use as a white food coloring because of a 2023 petition from Innophos Inc. of Cranbury, New Jersey. [1]

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.<ref name=Frassetto2011>Template:Cite journal</ref>

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.<ref>Template:Cite journal</ref>

• Urine crystals comparison.png

  Urine crystals comparison, with calcium phosphate crystal depicted at top center.

• 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.