Monobasic Sodium Phosphate USP NF Grade Specifications:
NaH2PO4 --- 119.98
NaH2PO4-H2O --- 137.99
NaH2PO4-2H2O --- 156.01
Phosphoric acid, monosodium salt, monohydrate;
Monosodium phosphate monohydrate CAS 10049-21-5
Phosphoric acid, monosodium salt, dihydrate;
Monosodium phosphate dihydrate CAS 13472-35-0
Anhydrous CAS 7558-80-7

DEFINITION
Monobasic Sodium Phosphate contains one or two molecules of water of hydration, or is anhydrous. It contains NLT 98.0% and NMT 103.0% of monobasic sodium phosphate (NaH2PO4), calculated on the anhydrous basis.

IDENTIFICATION
A. Identification Tests-General, Sodium
B. Identification Tests-General, Phosphate

ASSAY
Procedure
Sample: 2.5 g
Titrimetric system
Mode: Direct titration
Titrant: 1 N sodium hydroxide
Endpoint detection: Visual
Analysis: Dissolve the Sample in 10 mL of cold water. Add 20 mL of a cold, saturated solution of sodium chloride, add phenolphthalein, and then titrate with Titrant, keeping the temperature of the solution between 10C and 15C during the entire titration. Perform a blank determination and make any necessary correction. Each mL of Titrant is equivalent to 120.0 mg of monobasic sodium phosphate (NaH2PO4).
Acceptance criteria: 98.0% to 103.0% on the anhydrous basis

ASSAY
Procedure
Sample: 2.5 g
Titrimetric system
Mode: Direct titration
Titrant: 1 N sodium hydroxide
Endpoint detection: Visual
Analysis: Dissolve the Sample in 10 mL of cold water. Add 20 mL of a cold, saturated solution of sodium chloride, add phenolphthalein, and then titrate with Titrant, keeping the temperature of the solution between 10C and 15C during the entire titration. Perform a blank determination and make any necessary correction. Each mL of Titrant is equivalent to 120.0 mg of monobasic sodium phosphate (NaH2PO4).
Acceptance criteria: 98.0% to 103.0% on the anhydrous basis

Specifications of Sodium Dihydrogen Phosphate Monohydrate BP Ph Eur Grade
NaH2PO4-H2O, 138.0, CAS 10049-21-5
Action and use: Excipient.

DEFINITION
Sodium Dihydrogen Phosphate Monohydrate contains not less than 98.0% and not more than 100.5% of NaH2PO4, calculated with reference to the dried substance.

CHARACTERISTICS
Colourless crystals or a white powder.
Very soluble in water; very slightly soluble in ethanol (96%).
Dissolve 10.0 g in sufficient carbon dioxide-free water prepared from distilled water to produce 100 ml (solution S).

IDENTIFICATION
A. Solution S is faintly acid.
B. Solution S yields the reactions characteristic of phosphates.
C. Solution S neutralized with a 10% w/v solution of potassium hydroxide yields reaction A characteristic of sodium salts.
D. Complies with the test for Loss on drying.

TESTS
Acidity: pH of a mixture of 5 ml of solution S and 5 ml of carbon dioxide-free water , 4.2 to 4.5.
Clarity and colour of solution: Solution S is clear and colourless.
Arsenic: 0.5 g complies with the limit test for arsenic - 2 ppm.
Heavy metals: 12 ml of solution S complies with limit test A for heavy metals. Use lead standard solution (1 ppm Pb) to prepare the standard (10 ppm).
Iron: 10 ml of solution S complies with the limit test for - iron 10 ppm.
Chloride: Dilute 2.5 ml of solution S to 15 ml with water. The resulting solution complies with the limit test for chlorides - 200 ppm.
Sulphate: To 5 ml of solution S add 0.5 ml of hydrochloric acid and dilute to 15 ml with distilled water. The resulting solution complies with the limit test for sulphate - 300 ppm.
Reducing substances: To 5 ml of solution S add 0.25 ml of 0.02M potassium permanganate and 5 ml of 1M sulphuric acid and heat in a water bath for 5 minutes. The solution retains a slight red colour.
Loss on drying: When dried to constant weight at 130C, loses 11.5 to 14.5% of its weight. Use 0.5 g.

Specifications of Sodium Phosphate Monobasic FCC Food Grade
Monosodium Phosphate; Sodium Biphosphate;
Monosodium Dihydrogen Phosphate
NaH2PO4 Formula weight, anhydrous 119.98
NaH2PO4-H2O Formula weight, monohydrate 137.99
INS: 339(i) CAS: anhydrous CAS 7558-80-7
CAS: monohydrate 10049-21-5

DESCRIPTION
Sodium Phosphate, Monobasic, is anhydrous or contains one or two molecules of water of hydration and is slightly hygroscopic. The anhydrous form occurs as a white, crystalline powder or granules. The hydrated forms occur as white or transparent crystals or granules. All forms are freely soluble in water, but are insoluble in alcohol. The pH of a 1:100 solution is between 4.1 and 4.7.
Function: Buffer; emulsifier; nutrient.

Sodium Phosphate ACS Analytical Reagent Grade Specifications

Sodium Phosphate, Monobasic, Monohydrate
Sodium Dihydrogen Phosphate Monohydrate
NaH2PO4-H2O
Formula Weight 137.99
CAS Number 10049-21-5

REQUIREMENTS
Assay: 98.0-102.0% NaH2PO4 - H2O
pH of a 5% solution: 4.1-4.5 at 25C

MAXIMUM ALLOWABLE
Insoluble matter: 0.01%
Chloride (Cl): 5 ppm
Nitrogen compounds (as N): 0.001%
Sulfate (SO4): 0.003%
Calcium (Ca): 0.005%
Potassium (K): 0.01%
Heavy metals (as Pb): 0.001%
Iron (Fe): 0.001%