Tricalcium phosphate (sometimes abbreviated TCP) is a
calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar ...
salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
of
phosphoric acid with the
chemical formula
In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...
Ca
3(PO
4)
2. It is also known as tribasic calcium phosphate and bone phosphate of lime (BPL). It is a white solid of low solubility. Most commercial samples of "tricalcium phosphate" are in fact
hydroxyapatite
Hydroxyapatite, also called hydroxylapatite (HA), is a naturally occurring mineral form of calcium apatite with the formula Ca5(PO4)3(OH), but it is usually written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two entities. ...
.
It exists as three crystalline polymorphs α, α′, and β. The α and α′ states are stable at high temperatures.
Nomenclature
''Calcium phosphate'' refers to numerous materials consisting of calcium ions (Ca
2+) together with
orthophosphates (),
metaphosphates or
pyrophosphates () and occasionally oxide and
hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. ...
ions. Especially, the common mineral
apatite
Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the three most common ...
has formula Ca
5(PO
4)
3''X'', where ''X'' is
F,
Cl,
OH, or a mixture; it is
hydroxyapatite
Hydroxyapatite, also called hydroxylapatite (HA), is a naturally occurring mineral form of calcium apatite with the formula Ca5(PO4)3(OH), but it is usually written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two entities. ...
if the extra ion is mainly hydroxide. Much of the "tricalcium phosphate" on the market is actually powdered
hydroxyapatite
Hydroxyapatite, also called hydroxylapatite (HA), is a naturally occurring mineral form of calcium apatite with the formula Ca5(PO4)3(OH), but it is usually written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two entities. ...
.
Preparation
Tricalcium phosphate is produced commercially by treating
hydroxyapatite
Hydroxyapatite, also called hydroxylapatite (HA), is a naturally occurring mineral form of calcium apatite with the formula Ca5(PO4)3(OH), but it is usually written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two entities. ...
with
phosphoric acid and
slaked lime
Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca( OH)2. It is a colorless crystal or white powder and is produced when quicklime (calcium oxide) is mixed or slaked with water. It has m ...
.
[
It cannot be precipitated directly from aqueous solution. Typically double decomposition reactions are employed, involving a soluble phosphate and calcium salts, e.g. (NH4)2HPO4 + Ca(NO3)2.] is performed under carefully controlled pH conditions. The precipitate will either be "amorphous tricalcium phosphate", ATCP, or calcium deficient hydroxyapatite, CDHA, Ca9(HPO4)(PO4)5(OH), (note CDHA is sometimes termed apatitic calcium triphosphate). 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 the wet procedure entails heating a mixture of a calcium pyrophosphate and calcium carbonate:
:CaCO3 + Ca2P2O7 → Ca3(PO4)2 + CO2
Structure of β-, α- and α′- Ca3(PO4)2 polymorphs
Tricalcium phosphate has three recognised polymorphs, the rhombohedral β form (shown above), 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 All forms have complex structures consisting of tetrahedral phosphate centers linked through oxygen to the calcium ions. The high temperature forms each have two types of columns, one containing only calcium ions and the other both calcium and phosphate.
There are differences in chemical and biological properties between the beta and alpha forms, the α form is more soluble and biodegradable. Both forms are available commercially and are present in formulations used in medical and dental applications.
Occurrence
Calcium phosphate
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 whi ...
is one of the main combustion
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combus ...
products of bone
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...
(see bone ash
Bone ash is a white material produced by the calcination of bones. Typical bone ash consists of about 55.82% calcium oxide, 42.39% phosphorus pentoxide, and 1.79% water. The exact composition of these compounds varies depending upon the type of bo ...
). Calcium phosphate is also commonly derived from inorganic
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemist ...
sources such as mineral rock.
Tricalcium phosphate occurs naturally in several forms, including:
* as a rock in Morocco
Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to A ...
, Israel
Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...
, Philippines
The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no),
* bik, Republika kan Filipinas
* ceb, Republika sa Pilipinas
* cbk, República de Filipinas
* hil, Republ ...
, Egypt
Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a List of transcontinental countries, transcontinental country spanning the North Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via a land bridg ...
, and Kola
KOLA (99.9 FM) is a commercial radio station licensed to Redlands, California, and broadcasting to the Riverside-San Bernardino-Inland Empire radio market. It is owned by the Anaheim Broadcasting Corporation and it airs a classic hits radio form ...
(Russia
Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-ei ...
) 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
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with ...
animals
* in milk
Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digest solid food. Immune factors and immune-modulat ...
.
Biphasic tricalcium phosphate, BCP
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. It is a ceramic.
Preparation involves the sintering causing the irreversible decomposition of calcium deficient apatites alternatively termed non-stoichiometric apatites or basic calcium phosphate, an example is:
:Ca10−''δ''(PO4)6−''δ''(HPO4)''δ''(OH)2−''δ'' → (1−''δ'') Ca10(PO4)6(OH)2 + 3''δ'' Ca3(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.
Uses
Food additive
Tricalcium phosphate is used in powdered spices as an anticaking agent
An anticaking agent is an additive placed in powdered or granulated materials, such as table salt or confectioneries, to prevent the formation of lumps (caking) and for easing packaging, transport, flowability, and consumption. Caking mechanisms ...
, e.g. to prevent table salt from caking. The calcium phosphates have been assigned European food additive
Food additives are substances added to food to preserve Taste, flavor or enhance taste, appearance, or other sensory qualities. Some additives have been used for centuries as part of an effort to preserve food, for example vinegar (pickling), sal ...
number E341.
Health and beauty products
It is also found in baby powder
Baby powder is an astringent powder used for preventing diaper rash and for cosmetic uses. It may be composed of talc (in which case it is also called talcum powder) or corn starch. It may also contain additional ingredients like fragrances. ...
, antacids
An antacid is a substance which neutralizes stomach acidity and is used to relieve heartburn, indigestion or an upset stomach. Some antacids have been used in the treatment of constipation and diarrhea. Marketed antacids contain salts of alu ...
and toothpaste
Toothpaste is a paste or gel dentifrice used with a toothbrush to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it is an abrasive that aids in removing dental plaque and food from the teeth, ...
.[
]
Biomedical
It is also used as a nutritional supplement and occurs naturally in cow milk
Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digest solid food. Immune factors and immune-modulat ...
, although the most common and economical forms for supplementation are calcium carbonate (which should be taken with food) and calcium citrate
Calcium citrate is the calcium salt of citric acid. It is commonly used as a food additive ( E333), usually as a preservative, but sometimes for flavor. In this sense, it is similar to sodium citrate. Calcium citrate is also found in some die ...
(which can be taken without food). There is some debate about the different bioavailabilities of the different calcium salts.
It can be used as a tissue replacement for repairing bony defects when autogenous bone graft
Bone grafting is a surgical procedure that replaces missing bone in order to repair bone fractures that are extremely complex, pose a significant health risk to the patient, or fail to heal properly. Some small or acute fractures can be cured wit ...
is not feasible or possible. It may be used alone or in combination with a biodegradable
Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegrada ...
, resorbable polymer
A polymer (; Greek '' poly-'', "many" + '' -mer'', "part")
is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
such as polyglycolic acid. It may also be combined with autologous materials for a bone graft.
Porous beta-tricalcium phosphate scaffolds are employed as drug carrier systems for local drug delivery in bone.
Natural occurrence
Tuite Tuite is a surname. Notable people with the surname include:
* Aidan Tuite, Irish Gaelic footballer
* Gabrielle Tuite (born 1977), American model and actress
* Gerry Tuite (1910–1990), Australian rules footballer
* Hugh Morgan Tuite (1795–1868) ...
, a natural analogue of tricalcium orthophosphate(V), is a rare component of some meteorites. Its formation is related to shock metamorphism.Tuite
Mindat.org
References
{{Authority control
Biomaterials
Calcium compounds
Phosphates
E-number additives