Hypophosphorous Acid
H3PO2 66.00
Phosphinic acid;
Hypophosphorous acid
[6303-21-5].
(hye'' poe fos' for us as' id).
H3PO2 66.00
Phosphinic acid;
Hypophosphorous acid
[6303-21-5].DEFINITION
Hypophosphorous Acid contains NLT 30.0% and NMT 32.0% of H3PO2.
IDENTIFICATION
• A.
Hypophosphorous Acid yields a white precipitate with mercuric chloride TS. This precipitate becomes gray when an excess of hypophosphite is present.
• B.
Hypophosphorous Acid acidified with sulfuric acid and warmed with cupric sulfate TS yields a red precipitate.
ASSAY
• Procedure
Sample solution:
Pour 7 mL of Hypophosphorous Acid into a tared, glass-stoppered flask, and weigh. Dilute with about 25 mL of water, and add phenolphthalein TS.
Analysis:
Titrate with 1 N sodium hydroxide VS. Each mL of 1 N sodium hydroxide is equivalent to 66.00 mg of H3PO2.
Acceptance criteria:
30.0%–32.0%
IMPURITIES
Inorganic Impurities
• Heavy Metals, Method II 
231
231
Analysis:
Place 0.90 mL (1 g) of Hypophosphorous Acid in a small beaker, and add 3 mL of water. Add 1 mL of nitric acid, and evaporate on a steam bath to about 1 mL. Again add 1 mL of nitric acid, and evaporate on a steam bath. Dissolve the residue in 3 mL of water, add 6 N ammonium hydroxide until the solution is distinctly alkaline to litmus, then boil gently until the odor of ammonia disappears. Add 2 mL of 1 N acetic acid and 15 mL of warm water, filter, and dilute the filtrate with water to 25 mL.
Acceptance criteria:
NMT 20 ppm
SPECIFIC TESTS
• Limit of Barium and Oxalate
Sample solution:
Hypophosphorous Acid and water (1:3)
Analysis 1:
Neutralize 30 mL of the Sample solution with 6 N ammonium hydroxide: the mixture exhibits little or no precipitation. Filter, acidify 10 mL of the filtrate with hydrochloric acid, and add 2 mL of potassium sulfate TS.
Acceptance criteria 1:
No turbidity is produced (barium).
Analysis 2:
To a 10-mL portion of the filtrate obtained in Analysis 1, add 1 mL of calcium chloride TS.
Acceptance criteria 2:
The filtrate shows no turbidity upon the addition of the calcium chloride TS (oxalate).
ADDITIONAL REQUIREMENTS
• 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 1-301-816-8335 |
(EXC2010) Monographs - Excipients |
USP35–NF30 Page 1824
Pharmacopeial Forum: Volume No. 36(4) Page 947