Sodium citrate tribasic or Trisodium citrate, is a chemical compound, salt of citric acid, soluble in water. 

The name defines the structure of the molecule

• "Sodium". It's an alkali metal, symbol Na, with atomic number 11. It's an essential element for life and plays a key role in regulating blood pressure and plasma volume.
• "Citrate". It's the salt or ester of citric acid, a weak organic acid found in many plants, especially citrus fruits. It has the chemical formula C₆H₅O₇.
• "Tribasic". Indicates that citric acid has three acid groups (three carboxylic groups) and can thus form three different sodium salts.

Description of the raw materials used in its production:

• Citric Acid - A weak organic acid that's naturally found in citrus fruits like lemons and oranges.
• Sodium Hydroxide (NaOH) or Sodium Carbonate (Na₂CO₃) - Commonly known as caustic soda or soda ash, respectively.

Industrial chemical synthesis of Sodium Citrate Tribasic, step by step:

• Reaction - Citric acid is neutralized by gradually adding sodium hydroxide or sodium carbonate in an aqueous solution.
• Crystallization - Once the reaction is complete, the formed sodium citrate precipitates and crystallizes out of the solution.
• Filtration - The solution is then filtered to separate the crystallized sodium citrate from the remaining liquids.
• Drying - The crystals are then dried to remove any remaining moisture.
• Quality control - Once Sodium Citrate Tribasic is obtained, it undergoes various quality checks to ensure it meets specifications.

It appears as small crystals or a fine, white powder.

What it is used for and where

It is used in various applications: medical, pharmaceutical, cosmetic.

Food

It is used in beverages as an acidity corrector and antioxidant.

Labeled as E331 on the food additives list as an acidity regulator to restore pH to normal, it has also been shown to improve dough in baked goods as adding sodium citrate to dough produced improved gluten aggregation and increased gluten yield over the control by raising the pH and approaching the isoelectric point of glutenin and gliadin. In addition, sodium citrate resulted in an increased particle size distribution of the glutenin macropolymer (1).

For example, in cheese, the inclusion of sodium citrate resulted in expansion of the protein matrix and increase in cheese hardness.

Medical

Citrate plays a notable role in cellular metabolism and is an important intermediate in the tricarboxylic acid cycle. In medicine it is used as an anticoagulant in stored blood, and for alkalinization of urine in the prevention of kidney stones.

In medicine, infused sodium citrate resulted in acidification and anticoagulation of blood similar to lactic acid and sodium citrate, respectively, without affecting blood gas analysis (2). 

Kidney stones affect people all over the world and have a high recurrence rate even with treatment. Citrate salts prevent new stone formation and reduce further stone growth in patients with residual stones that contain predominantly oxalate (3).

The results of this study demonstrated that treatment with sodium citrate at higher concentrations or for longer periods exerts a cytotoxic effect on AGS cells through induction of the intrinsic apoptosis pathway and alteration of the levels of certain cytokines (4).

In toothpastes, the addition of sodium citrate improved dentin sensitivity (5).

Cosmetics

In cosmetics, the inclusion of sodium citrate in the formula allows to maintain the pH at acceptable levels and to regulate the overall acidity level.

Buffering agent. It is an iingredient that can bring an alkaline or acid solution to a certain pH level and prevent it from changing, in practice a pH stabiliser that can effectively resist instability and pH change.

Chelating agent. It has the function of preventing unstable reactions and improving the bioavailability of chemical components within a product, and removes calcium and magnesium cations that can cause cloudiness in clear liquids.

Fragrance. It plays a decisive and important role in the formulation of cosmetic products as it provides the possibility of enhancing, masking or adding fragrance to the final product, increasing its marketability.  The consumer always expects to find a pleasant or distinctive scent in a cosmetic product.

Other uses

Pharmaceuticals. Used as an alkalinizing agent in dialysis solutions and as an anticoagulant in blood for transfusions.

Water Treatment. Used as a softening agent in water softeners.

Chemical Industry. Used in the production of detergents and soaps to adjust pH.

Sodium citrate studies

Optimal typical characteristics of the commercial product sodium citrate

Where to buy sodium citrate

• Molecular Formula : C₆H₅Na₃O₇.₂H₂O     Na₃(C₆H₅O₇)
• Linear Formula :  HOC(COONa)(CH₂COONa)₂ · ₂H₂O
• Molecular Weight :  258.068 g/mol
• CAS : 68-04-2
• EC Number : 200-675-3   213-618-2   200-675-3
• UNII   RS7A450LGA
• DSSTox Substance ID: DTXSID2026363     DTXSID1027348
• MDL number  MFCD00012462
• PubChem Substance ID 24899674
• InChl  1S/C6H8O7.3Na/c7-3(8)1-6(13,5(11)12)2-4(9)10;;;/h13H,1-2H2,(H,7,8)(H,9,10)(H,11,12);;;/q;3*+1/p-3
• InChI Key      HRXKRNGNAMMEHJ-UHFFFAOYSA-K
• SMILES    C(C(=O)[O-])C(CC(=O)[O-])(C(=O)[O-])O.[Na+].[Na+].[Na+]
• IUPAC   trisodium;2-hydroxypropane-1,2,3-tricarboxylate
• ChEBI    53258
• FEMA   3026
• NACRES  NA.25

Synonyms :

• Trisodium citrate
• Trisodium citrate, anhydrous
• Citrosodine
• Sodium citrate anhydrous
• Trisodium 2-hydroxy-1,2,3-propanetricarboxylate
• 1,2,3-Propanetricarboxylic acid, 2-hydroxy-, trisodium salt

References_____________________________________________________________________

(1) Amiri A, Farshi-Marandi P, Shahedi M. Impact of sodium citrate on structural properties of gluten. J Food Sci Technol. 2019 Feb;56(2):1090-1093. doi: 10.1007/s13197-019-03571-6.

(2) Scaravilli V, Di Girolamo L, Scotti E, Busana M, Biancolilli O, Leonardi P, Carlin A, Lonati C, Panigada M, Pesenti A, Zanella A. Effects of sodium citrate, citric acid and lactic acid on human blood coagulation. Perfusion. 2018 Oct;33(7):577-583. doi: 10.1177/0267659118777441.

(3) Phillips R, Hanchanale VS, Myatt A, Somani B, Nabi G, Biyani CS. Citrate salts for preventing and treating calcium containing kidney stones in adults. Cochrane Database Syst Rev. 2015 Oct 6;(10):CD010057. doi: 10.1002/14651858.CD010057.pub2.

(4) Xia Y, Zhang X, Bo A, Sun J, Li M. Sodium citrate inhibits the proliferation of human gastric adenocarcinoma epithelia cells. Oncol Lett. 2018 May;15(5):6622-6628. doi: 10.3892/ol.2018.8111.

(5) Clark DC, Al-Joburi W, Chan EC. The efficacy of a new dentifrice in treating dentin sensitivity: effects of sodium citrate and sodium fluoride as active ingredients. J Periodontal Res. 1987 Mar;22(2):89-93. doi: 10.1111/j.1600-0765.1987.tb01545.x.