Sodium citrate dihydrate

• BPSodium Citrate
• JPSodium Citrate Hydrate
• Ph. Eur.Sodium Citrate
• USP–NFSodium Citrate

Citric acid trisodium salt dihydrate; natrii citras; trisodium citrate dihydrate; E331

Trisodium 2-hydroxypropane-1,2,3-tricarboxylate dihydrate · [6132-04-3]

UNII B22547B95K · PubChem CID 71474

C6H5Na3O7·2H2O · 294.10

pH adjuster, buffering agent

Typical concentrations: — · Dosage forms: Liquid, Sterile (parenteral/ophthalmic)

Sodium citrate is used, alone or with citric acid, as a buffering agent and pH adjuster in oral, parenteral, ophthalmic and topical preparations, typically at concentrations up to a few per cent. It is also used as a sequestering agent, as an alkalising agent, as an anticoagulant in blood-collection and apheresis solutions (for example acid–citrate–dextrose), in effervescent products and to mask the taste of acidic ingredients. In foods it is used as an emulsifying salt and acidity regulator.

Odourless, colourless crystals or a white crystalline powder with a cooling, saline taste. It is slightly deliquescent in moist air and the crystals are efflorescent in warm, dry air.

Water content

11.0–13.0% w/w

pH

mildly alkaline, about 7.5–8.5 for a 5% w/v aqueous solution

pKa values (citric acid)

about 3.1, 4.8 and 6.4

Solubility

freely soluble in water; practically insoluble in ethanol

Dehydration

loses its water of crystallisation at about 150 °C

A stable material. Aqueous solutions may be sterilised by autoclaving. On storage, solutions may cause separation of small solid particles from glass containers. Store in an airtight container in a cool, dry place.

Aqueous solutions are slightly alkaline and react with acidic substances. Alkaloidal salts may be precipitated from their solutions, and calcium and strontium salts precipitate the corresponding citrates. Other incompatibilities include bases, reducing agents and oxidising agents.

Prepared by neutralising citric acid with sodium hydroxide or sodium carbonate and crystallising the dihydrate from the solution. Citric acid itself is produced by fermentation, mainly with Aspergillus niger.

Citrate is metabolised to bicarbonate and is generally regarded as non-toxic and non-irritant at excipient levels. Large doses can cause metabolic alkalosis, and rapid infusion of citrate-containing blood products can lower ionised calcium and cause hypocalcaemic symptoms.

Observe normal precautions for the quantity handled. Eye protection and gloves are recommended.

GRAS listed. Accepted as a food additive in Europe (E331). Included in the FDA Inactive Ingredient Database (inhalation, injections, ophthalmic, oral, nasal, otic, rectal, topical and vaginal preparations) and in parenteral and non-parenteral medicines licensed in Europe.

Citric acid monohydrate; potassium citrate; sodium citrate, anhydrous.

Citrate buffers cover a wide pH range (about pH 2.5–6.5) because citric acid has three ionisable groups. Citrate-buffered injections can cause stinging on subcutaneous injection, and citrate can chelate metal ions required by some formulations.