Name: Sodium Phosphate, Dibasic
CAS No: Anhydrous dibasic sodium phosphate [7558-79-4], Dibasic sodium phosphate dihydrate [10028-24-7], Dibasic sodium phosphate dodecahydrate [10039-32-4], Dibasic sodium phosphate heptahydrate [7782-85-6], Dibasic sodium phosphate hydrate [10140-65-5], Dibasic sodium phosphate monohydrate [118830-14-1]
BP: Anhydrous Disodium Hydrogen Phosphate Disodium Hydrogen Phosphate Dihydrate Disodium Hydrogen Phosphate Dodecahydrate JP: Dibasic Sodium Phosphate Hydrate PhEur: Disodium Phosphate, Anhydrous Disodium Phosphate Dihydrate Disodium Phosphate Dodecahydrate USP: Dibasic Sodium Phosphate
Dinatrii phosphas anhydricus; dinatrii phosphas dihydricus; dinatrii phosphas dodecahydricus; disodium hydrogen phosphate; disodium phosphate; E339; phosphoric acid, disodium salt; secondary sodium phosphate; sodium orthophosphate
Anhydrous dibasic sodium phosphate [7558-79-4], Dibasic sodium phosphate dihydrate [10028-24-7], Dibasic sodium phosphate dodecahydrate [10039-32-4], Dibasic sodium phosphate heptahydrate [7782-85-6], Dibasic sodium phosphate hydrate [10140-65-5], Dibasic sodium phosphate monohydrate [118830-14-1]
Na2HPO4 141.96 Na2HPO4H2O 159.94 Na2HPO42H2O 177.98 Na2HPO47H2O 268.03 Na2HPO412H2O 358.08
See Section 4.
Dibasic sodium phosphate is used in a wide variety of pharmaceutical formulations as a buffering agent and as a sequestering agent. Therapeutically, dibasic sodium phosphate is used as a mild laxative and in the treatment of hypophosphatemia.(1,2) Dibasic sodium phosphate is also used in food products; for example as an emulsifier in processed cheese.
The USP 32 states that dibasic sodium phosphate is dried or contains, 1, 2, 7, or 12 molecules of water of hydration. Anhydrous dibasic sodium phosphate occurs as a white powder. The dihydrate occurs as white or almost white, odorless crystals. The heptahydrate occurs as colorless crystals or as a white granular or caked salt that effloresces in warm, dry air. The dodecahydrate occurs as strongly efflorescent, colorless or transparent crystals
See Table I.
Acidity/alkalinity pH = 9.1 for a 1% w/v aqueous solution of the anhydrous material at 258C. A saturated aqueous solution of the dodecahydrate has a pH of about 9.5. Ionization constants PKa1 = 2.15 at 258C;(3) pKa2 = 7.20 at 258C; pKa3 = 12.38 at 258C. Moisture content The anhydrous form is hygroscopic and will absorb up to 7 moles of water on exposure to air, whereas the heptahydrate is stable in air. NIR spectra see Figure 1. Osmolarity A 2.23% w/v aqueous solution of the dihydrate is isoosmotic with serum; a 4.45% w/v aqueous solution of the dodecahydrate is isoosmotic with serum. Solubility Very soluble in water, more so in hot or boiling water; practically insoluble in ethanol (95%). The anhydrous material
The anhydrous form of dibasic sodium phosphate is hygroscopic. When heated to 408C, the dodecahydrate fuses; at 1008C it loses its water of crystallization; and at a dull-red heat (about 2408C) it is converted into the pyrophosphate, Na4P2O7. Aqueous solutions of dibasic sodium phosphate are stable and may be sterilized by autoclaving. The bulk material should be stored in an airtight container, in a cool, dry place.
Dibasic sodium phosphate is incompatible with alkaloids, antipyrine, chloral hydrate, lead acetate, pyrogallol, resorcinol and calcium gluconate, and ciprofloxacin.(4) Interaction between calcium and phosphate, leading to the formation of insoluble calcium–phosphate precipitates, is possible in parenteral admixtures
Either bone phosphate (bone ash), obtained by heating bones to whiteness, or the mineral phosphorite is used as a source of tribasic calcium phosphate, which is the starting material in the industrial production of dibasic sodium phosphate. Tribasic calcium phosphate is finely ground and digested with sulfuric acid. This mixture is then leached with hot water and neutralized with sodium carbonate, and dibasic sodium phosphate is crystallized from the filtrate.
Dibasic sodium phosphate is widely used as an excipient in parenteral, oral, and topical pharmaceutical formulations. Phosphate occurs extensively in the body and is involved in many physiological processes since it is the principal anion of intracellular fluid. Most foods contain adequate amounts of phosphate, making hypophosphatemia (phosphate deficiency)(1) virtually unknown except for certain disease states(2) or in patients receiving total parenteral nutrition. Treatment is usually by the oral administration of up to 100 mmol of phosphate daily. Approximately two-thirds of ingested phosphate is absorbed from the gastrointestinal tract, virtually all of it being excreted in the urine, and the remainder is excreted in the feces. Excessive administration of phosphate, particularly intravenously, rectally, or in patients with renal failure, can cause hyperphosphatemia that may lead to hypocalcemia or other severe electrolyte imbalances.(5,6) Adverse effects occur less frequently following oral consumption, although phosphates act as mild saline laxatives when administered orally or rectally. Consequently, gastrointestinal disturbances including diarrhea, nausea, and vomiting may occur following the use of dibasic sodium phosphate as an excipient in oral formulations. However, the level of dibasic sodium phosphate used as an excipient in a pharmaceutical formulation is not usually associated with adverse effects. LD50 (rat, oral): 17 g/kg(7)
Observe normal precautions appropriate to the circumstances and quantity of material handled. Dibasic sodium phosphate may be irritating to the skin, eyes, and mucous membranes. Eye protection and gloves are recommended.
GRAS listed. Accepted in Europe for use as a food additive. Included in the FDA Inactive Ingredients Database (injections; infusions; nasal, ophthalmic, oral, otic, topical, and vaginal preparations). Included in nonparenteral and parenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients
Dibasic potassium phosphate; sodium phosphate, monobasic; tribasic sodium phosphate. Dibasic potassium phosphate Empirical formula K2HPO4 Molecular weight 174.15 CAS number [7758-11-4] Synonyms Dipotassium hydrogen orthophosphate; dipotassium hydrogen phosphate; dipotassium phosphate; E340; potassium phosphate. Appearance Colorless or white, granular, hygroscopic powder. Acidity/alkalinity pH = 8.5–9.6 for a 5% w/v aqueous solution at 258C. Osmolarity A 2.08% w/v aqueous solution of dibasic potassium phosphate is isoosmotic with serum. Solubility Freely soluble in water; very slightly soluble in ethanol (95%). Comments One gram of dibasic potassium phosphate contains approximately 11.5 mmol of potassium and 5.7 mmol of phosphate. Tribasic sodium phosphate Empirical formula Na3PO4xH2O Molecular weight 163.94 for the anhydrous material 380.06 for the dodecahydrate (12H2O) CAS number [7601-54-9] for the anhydrous material. Synonyms E339; trisodium orthophosphate; trisodium phosphate; TSP. Acidity/alkalinity pH = 12.1 for a 1% w/v aqueous solution of the anhydrous material at 258C. A 1% w/v aqueous solution of the dodecahydrate at 258C has a pH of 12.0–12.2. Density 1.3 g/cm3 for the anhydrous material; 0.9 g/cm3 for the dodecahydrate. Solubility The anhydrous material is soluble 1 in 8 parts of water, while the dodecahydrate is soluble 1 in 5 parts of water at 208C.
One gram of anhydrous dibasic sodium phosphate represents approximately 14.1 mmol of sodium and 7.0 mmol of phosphate. One gram of dibasic sodium phosphate dihydrate represents approximately 11.2 mmol of sodium and 5.6 mmol of phosphate. One gram of dibasic sodium phosphate heptahydrate represents approximately 7.5 mmol of sodium and 3.7 mmol of phosphate. One gram of dibasic sodium phosphate dodecahydrate represents approximately 5.6 mmol of sodium and 2.8 mmol of phosphate. A specification for sodium phosphate, dibasic is contained in the Food Chemicals Codex (FCC).(8) The PubChem Compound ID (CID) for anhydrous dibasic sodium phosphate is 24203, and for dibasic sodium phosphate dodecahydrate is 61456.