Dibasic Potassium Phosphate USP Grade Specifications:
K2HPO4 --- 174.18
Phosphoric acid, dipotassium salt;
Dipotassium hydrogen phosphate CAS 7758-11-4

DEFINITION
Dibasic Potassium Phosphate contains NLT 98.0% and NMT 100.5% of K2HPO4, calculated on the dried basis.

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

ASSAY
Procedure
Sample: 5.2 g
Sample solution: Transfer the Sample to a 250-mL beaker. Add 50 mL of water and 40.0 mL of 1 N hydrochloric acid and stir until dissolved.
Blank: Transfer 40.0 mL of 1 N hydrochloric acid to a 250-mL beaker. Add 50 mL of water.
Analysis: Titrate the Blank with 1 N sodium hydroxide and record the volume of 1 N sodium hydroxide consumed. Titrate the excess acid in the Sample solution with 1 N sodium hydroxide to the inflection point at pH 4 and record the burette reading. Subtract this burette reading from that of the blank and designate the volume of 1 N sodium hydroxide resulting from this subtraction as A. Continue the titration with 1 N sodium hydroxide to the inflection point at pH 8.8, record the burette reading, and calculate the volume (B) of 1 N sodium hydroxide required in the titration between the two inflection points (pH 4 to 8.8). Where A is equal to or less than B, each mL of the volume A of 1 N sodium hydroxide is equivalent to 174.2 mg of K2HPO4. Where A is greater than B, each mL of the volume 2B - A of 1 N sodium hydroxide is equivalent to 174.2 mg of K2HPO4.
Acceptance criteria: 98.0%-100.5% on the dried basis.

Insoluble Substances: Sample solution: Dissolve 10 g in 100 mL of hot water. Analysis: Filter the Sample solution through a tared filtering crucible, wash the insoluble residue with hot water, and dry at 105C for 2 h. Acceptance criteria: The weight of the residue is NMT 20 mg (NMT 0.2%).

Carbonate: Sample: 1 g Analysis: Add 3 mL of water and 2 mL of 3 N hydrochloric acid to the Sample. Acceptance criteria: NMT a few bubbles are evolved.

Chloride and Sulfate, Chloride: Sample: 1.0 g

Acceptance criteria: Shows no more chloride than corresponds to 0.40 mL of 0.020 N hydrochloric acid (NMT 0.03%)

Acceptance criteria: Shows no more sulfate than corresponds to 0.20 mL of 0.020 N sulfuric acid (NMT 0.1%)

Arsenic: NMT 3 ppm

Iron: Sample solution: Dissolve 0.33 g in 10 mL of water. Analysis: To the Sample solution add 6 mL of hydroxylamine hydrochloride solution (1 in 10) and 4 mL of orthophenanthroline solution prepared by dissolving 1 g of orthophenanthroline in 1000 mL of water containing 1 mL of 3 N hydrochloric acid, and dilute with water to 25 mL.

Acceptance criteria: Any red color produced within 1 h is not darker than that of a control prepared from 1 mL of Standard Iron Solution: NMT 30 ppm.

Sodium: A solution (1 in 10) tested on a platinum wire imparts no pronounced yellow color to a nonluminous flame.

Limit of Fluoride: To pass the test.

Acceptance criteria: NMT 0.001%

Limit of Monobasic or Tribasic Salt: Sample solution: Dissolve 3 g in 30 mL of water, and cool to 20C. Analysis: Add 3 drops of thymol blue to the Sample solution.

Acceptance criteria: A blue color is produced, which is changed to yellow (with a greenish tinge) by the addition of NMT 0.4 mL of 1 N hydrochloric acid. pH: 8.5-9.6, in a solution (1 in 20)

Loss on Drying: Dry a sample at 105C to constant weight: it loses NMT 1.0% of its weight. Packaging and Storage: Preserve in well-closed containers.

Specifications of Dipotassium Hydrogen Phosphate BP Ph Eur Grade
Dipotassium Phosphate BP Ph Eur
K2HPO4 -- 174.2 -- CAS 7758-11-4
Dibasic Potassium Phosphate
Potassium Phosphate Dibasic

DEFINITION
Dipotassium phosphate contains not less than 98.0 per cent and not more than the equivalent of 101.0 per cent of K2HPO4, calculated with reference to the dried substance.

CHARACTERS
A white powder or colourless crystals, very hygroscopic, very soluble in water, very slightly soluble in alcohol.

IDENTIFICATION
A. Solution S (see Tests) is slightly alkaline
B. Solution S gives reaction of phosphates.
C. Solution S gives reaction of potassium.

TESTS
Solution S: Dissolve 5.0 g in distilled water and dilute to 50 ml with the same solvent.
Appearance of solution: Solution S is clear and colourless.
Reducing substances: Heat on a water-bath for 5 min a mixture of 5 ml of solution S, 5 ml of dilute sulphuric acid and 0.25 ml of 0.02 M potassium permanganate. The solution remains faintly pink.
Chlorides: To 2.5 ml of solution S add 10 ml of dilute nitric acid and dilute to 15 ml with water. The solution complies with the limit test for chlorides (200 ppm).
Sulphates: To 1.5 ml of solution S add 2 ml of dilute hydrochloric acid and dilute to 15 ml with distilled water. The solution complies with the limit test for sulphates (0.1 per cent).
Arsenic: 5 ml of solution S complies with limit test A for arsenic (2 ppm).
Iron: 10 ml of solution S complies with the limit test for iron (10 ppm).
Heavy metals: Dissolve 2.0 g in 8 ml of water. Acidify with about 6 ml of dilute hydrochloric acid (pH 3 to 4) and dilute to 20 ml with water. 12 ml of the solution complies with limit test A for heavy metals (10 ppm).
Sodium: If intended for use in the manufacture of parenteral dosage forms, it contains not more than 0.1 per cent of Na, determined by atomic emission spectrometry.
Loss on drying: Not more than 2.0 per cent, determined on 1.000 g by drying in an oven at 125C to 130C.
Bacterial endotoxins: Less than 1.1 IU/mg, if intended for use in the manufacture of parenteral dosage forms without a further appropriate procedure for the removal of bacterial endotoxins.

Specifications of Potassium Phosphate Dibasic FCC Food Grade
Dipotassium Monophosphate, Dipotassium Phosphate FCC Food Grade
Dibasic Potassium Phosphate FCC
K2HPO4 Formula wt 174.18
INS: 340(ii) CAS: 7758-11-4

DESCRIPTION
Potassium Phosphate, Dibasic, occurs as a colorless or white, granular salt that is deliquescent when exposed to moist air. One gram is soluble in about 3 mL of water. It is insoluble in alcohol. The pH of a 1% solution is about 9.
Function: Buffer; sequestrant; yeast food.

REQUIREMENTS
Identification: A 1:20 aqueous solution gives positive tests for Potassium and for Phosphate.
Assay: Not less than 98.0% of K2HPO4 after drying.
Arsenic: Not more than 3 mg/kg.
Fluoride: Not more than 10 mg/kg.
Insoluble Substances: Not more than 0.2%.
Lead: Not more than 2 mg/kg.
Loss on Drying: Not more than 2.0%.