Ammonium Phosphate

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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(NH₄)₂HPO₄          132.06

Phosphoric acid, diammonium salt;

Diammonium phosphate CAS RN:  7783-28-0.

1 DEFINITION

Ammonium Phosphate contains NLT 96.0% and NMT 102.0% of (NH₄)₂HPO₄

2 IDENTIFICATION

A. IDENTIFICATION TESTS-GENERAL, Ammonium (191); A solution (1 in 20) meets the requirements.

B. IDENTIFICATION TESTS GENERAL, Phosphate (191): A solution (1 in 20) meets the requirements.

3 ASSAY

3.1 PROCEDURE

3.1.1 Sample

600 mg of Ammonium Phosphate

3.1.2 Titrimetric system

(See Titrimetry (541).)

• Mode: Direct titration
• Titrant: 0.1 N sulfuric acid VS
• Endpoint detection: potentiometric

3.1.3 Analysis

Dissolve the Sample in 40 mL of water, and titrate with 0.1 N sulfuric acid VS to a pH of 4.6. Each mL of 0.1 N sulfuric acid is equivalent to 13.21 mg of (NH), HPO

3.1.4 Acceptance criteria

96.0%-102.0%

4 IMPURITIES

CHLORIDE AND SULFATE, Chloride (221): A 1.0-g portion shows no more chloride than corresponds to 0.40 mL of 0.020 N hydrochloric acid

(0.03%).

CHLORIDE AND SULFATE, Sulfate (221); A 0.20-g portion shows no more sulfate than corresponds to 0.30 mL of 0.020 N sulfuric acid (0.15%).

Change to read:

ARSENIC (211), Procedures, Procedure 1 (CN 1-JUN-2023): NMT 3 ppm

5 SPECIFIC TESTS

PH (791): 7.6-8.2, in a solution (1 in 100)

6 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in tight containers.