Calcium citrate

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Calcium citrate
Calciumcitrat V2.svg
2D structure of calcium citrate
Ca-citrate-tetrahydrate.png
Calcium citrate tetrahydrate [1]
Calcium citrate.jpg
Calcium citrate tetrahydrate
Names
IUPAC name
2-hydroxy-1,2,3-propane-tricarboxylic acid calcium salt (2:3)
Other names
E333, tricalcium dicitrate
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.011.265 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 212-391-7
E number E333 (antioxidants, ...)
PubChem CID
UNII
  • InChI=1S/2C6H8O7.3Ca/c2*7-3(8)1-6(13,5(11)12)2-4(9)10;;;/h2*13H,1-2H2,(H,7,8)(H,9,10)(H,11,12);;;/q;;3*+2/p-6 Yes check.svgY
    Key: FNAQSUUGMSOBHW-UHFFFAOYSA-H Yes check.svgY
  • InChI=1/2C6H8O7.3Ca/c2*7-3(8)1-6(13,5(11)12)2-4(9)10;;;/h2*13H,1-2H2,(H,7,8)(H,9,10)(H,11,12);;;/q;;3*+2/p-6
    Key: FNAQSUUGMSOBHW-CYFPFDDLAZ
  • [Ca+2].[Ca+2].[Ca+2].O=C([O-])CC(O)(C([O-])=O)CC(=O)[O-].[O-]C(=O)C(O)(CC([O-])=O)CC([O-])=O
Properties
Ca3(C6H5O7)2
Molar mass 498.4334 g/mol (anhydrous)
570.4945 g/mol (tetrahydrate)
AppearanceWhite powder
Odor odorless
Density 1.63 g/cm3 (anhydrous)
2.00 g/cm3 (tetrahydrate) [1]
Melting point Decomposes
Boiling point Decomposes
0.85 g/L (18 °C)
0.95 g/L (25 °C)
Solubility insoluble in alcohol
Structure
Triclinic (tetrahydrate)
P1, No. 2
a = 0.59466(4) nm, b = 1.02247(8) nm, c = 1.66496(13) nm
α = 72.213(7)°, β = 79.718(7)°, γ = 89.791(6)° [1]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Irritant
NFPA 704 (fire diamond)
NFPA 704.svgHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
1
0
Related compounds
Other cations
Magnesium citrate
Strontium citrate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

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 dietary calcium supplements (e.g. Citracal or Caltrate). Calcium makes up 24.1% of calcium citrate (anhydrous) and 21.1% of calcium citrate (tetrahydrate) by mass. The tetrahydrate occurs in nature as the mineral Earlandite.

Contents

Chemical properties

Calcium citrate is sparingly soluble in water. Needle-shaped crystals of tricalcium dicitrate tetrahydrate [Ca3(C6H5O7)2(H2O)2]·2H2O were obtained by hydrothermal synthesis. The crystal structure comprises a three-dimensional network in which eightfold coordinated Ca2+ cations are linked by citrate anions and hydrogen bonds between two non-coordinating crystal water molecules and two coordinating water molecules. [1]

Production

Calcium citrate is an intermediate in the isolation of citric acid from the fungal fermentation process by which citric acid is produced industrially. [2] The citric acid in the broth solution is neutralized by limewater, precipitating insoluble calcium citrate. This is then filtered off from the rest of the broth and washed to give clean calcium citrate.

3 Ca(OH)2(s) + 2 C6H8O7(l) → Ca3(C6H5O7)2(s) + 6 H2O(l)

The calcium citrate thus produced may be sold as-is, or it may be converted to citric acid using dilute sulfuric acid.

Medical uses

It's primarily sold as a food supplement of calcium.

Bioavailability

In many individuals, bioavailability of calcium citrate is found to be equal to that of the cheaper calcium carbonate (CaCO3). [3] However, alterations to the digestive tract may change how calcium is digested and absorbed. Unlike calcium carbonate, which is basic and neutralizes stomach acid, calcium citrate has no effect on stomach acid. [4] [ better source needed ] Calcium carbonate is harder to digest than calcium citrate, [4] and calcium carbonate carries a risk of "acid rebound" (the stomach overcompensates by producing more acid), [4] so individuals who are sensitive to antacids or who have difficulty producing adequate stomach acid may choose calcium citrate over calcium carbonate for supplementation.

According to a 2009 research into calcium absorption after gastric bypass surgery, [5] calcium citrate may have improved bioavailability over calcium carbonate in Roux-en-Y gastric bypass patients who are taking calcium citrate as a dietary supplement after surgery. This is mainly due to the changes related to where calcium absorption occurs in the digestive tract of these individuals.

See also

Related Research Articles

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<span class="mw-page-title-main">Kidney stone disease</span> Formation of mineral stones in the urinary tract

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<span class="mw-page-title-main">Calcium carbonate</span> Chemical compound

Calcium carbonate is a chemical compound with the chemical formula CaCO3. It is a common substance found in rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skeletons and pearls. Materials containing much calcium carbonate or resembling it are described as calcareous. Calcium carbonate is the active ingredient in agricultural lime and is produced when calcium ions in hard water react with carbonate ions to form limescale. It has medical use as a calcium supplement or as an antacid, but excessive consumption can be hazardous and cause hypercalcemia and digestive issues.

<span class="mw-page-title-main">Citric acid</span> Weak organic acid

Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms.

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Calcium pyrophosphate (Ca2P2O7) is a chemical compound, an insoluble calcium salt containing the pyrophosphate anion. There are a number of forms reported: an anhydrous form, a dihydrate, Ca2P2O7·2H2O and a tetrahydrate, Ca2P2O7·4H2O. Deposition of dihydrate crystals in cartilage are responsible for the severe joint pain in cases of calcium pyrophosphate deposition disease (pseudo gout) whose symptoms are similar to those of gout. Ca2P2O7 is commonly used as a mild abrasive agent in toothpastes, because of its insolubility and nonreactivity toward fluoride.

<span class="mw-page-title-main">Dicalcium phosphate</span> Chemical compound

Dicalcium phosphate is the calcium phosphate with the formula CaHPO4 and its dihydrate. The "di" prefix in the common name arises because the formation of the HPO42– anion involves the removal of two protons from phosphoric acid, H3PO4. It is also known as dibasic calcium phosphate or calcium monohydrogen phosphate. Dicalcium phosphate is used as a food additive, it is found in some toothpastes as a polishing agent and is a biomaterial.

Calcium citrate malate is a water-soluble calcium supplement. It is the calcium salt of citric acid and malic acid with variable composition.

<span class="mw-page-title-main">Magnesium citrate</span> Chemical compound

Magnesium citrate is a magnesium preparation in salt form with citric acid in a 1:1 ratio. It contains 11.23% magnesium by weight.

<span class="mw-page-title-main">Calcium formate</span> Chemical compound

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<span class="mw-page-title-main">Calcium sulfite</span> Chemical compound

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<span class="mw-page-title-main">Earlandite</span>

Earlandite, [Ca3(C6H5O7)2(H2O)2]·2H2O, is the mineral form of calcium citrate tetrahydrate. It was first reported in 1936 and named after the English microscopist and oceanographer Arthur Earland FRSE. Earlandite occurs as warty fine-grained nodules ca. 1 mm in size in bottom sediments of the Weddell Sea, off Antarctica. Its crystal symmetry was first assigned as orthorhombic, then as monoclinic, and finally as triclinic.

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References

  1. 1 2 3 4 Herdtweck E, Kornprobst T, Sieber R, Straver L, Plank J (2011). "Crystal Structure, Synthesis, and Properties of tri-Calcium di-Citrate tetra-Hydrate [Ca3(C6H5O7)2(H2O)2]·2H2O". Zeitschrift für anorganische und allgemeine Chemie. 637 (6): 655–659. doi:10.1002/zaac.201100088.
  2. "Use of Lime in the Chemical Industry". National Lime Association. Archived from the original on 2006-09-29. Retrieved 2006-11-25.
  3. Heaney RP, Dowell MS, Bierman J, Hale CA, Bendich A (2001). "Absorbability and cost-effectiveness in calcium supplementation". Journal of the American College of Nutrition . 20 (3): 239–46. doi:10.1080/07315724.2001.10719038. PMID   11444420. S2CID   206488.
  4. 1 2 3 "What you need to know about calcium". Harvard Health Publications. 9 June 2009. Retrieved 4 August 2014.
  5. Tondapu P, Provost D, Adams-Huet B, Sims T, Chang C, Sakhaee K (June 2009). "Comparison of the Absorption of Calcium Carbonate and Calcium Citrate after Roux-en-Y Gastric Bypass". Obesity Surgery. 19 (9): 1256–1261. doi:10.1007/s11695-009-9850-6. PMC   4469176 . PMID   19437082.