Ammonium Phosphate
(a moe' nee um fos' fate).

(NH4)2HPO4 132.06
Phosphoric acid, diammonium salt;    
Diammonium phosphate     [7783-28-0].
Ammonium Phosphate contains NLT 96.0% and NMT 102.0% of (NH4)2HPO4.
•  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.
•  Procedure
Sample:  600 mg of Ammonium Phosphate
Titrimetric system 
Mode:  Direct titration
Titrant:  0.1 N sulfuric acid VS
Endpoint detection:  potentiometric
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 (NH4)2HPO4.
Acceptance criteria:  96.0%–102.0%
•  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%).
•  Arsenic, Method I 211: NMT 3 ppm
•  Heavy Metals 231
Test preparation:  Dissolve 2.0 g in 25 mL of water.
Acceptance criteria:  NMT 10 ppm
•  pH 791: 7.6–8.2, in a solution (1 in 100)
•  Packaging and Storage: Preserve in tight containers.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Robert H. Lafaver, M.S.
Scientific Liaison
(EXC2010) Monographs - Excipients
USP35–NF30 Page 1699