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Pyrimethamine
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C12H13ClN4 248.71

2,4-Pyrimidinediamine, 5-(4-chlorophenyl)-6-ethyl-.
2,4-Diamino-5-(p-chlorophenyl)-6-ethylpyrimidine [58-14-0].
» Pyrimethamine contains not less than 99.0 percent and not more than 101.0 percent of C12H13ClN4, calculated on the dried basis.
Packaging and storage— Preserve in tight, light-resistant containers.
Identification—
B: Mix about 100 mg with 500 mg of anhydrous sodium carbonate, and ignite the mixture. Cool, add 5 mL of hot water, heat for 5 minutes on a steam bath, filter, and neutralize the filtrate with nitric acid: the solution responds to the test for Chloride 191.
Melting range 741: between 238 and 242.
Loss on drying 731 Dry it at 105 for 4 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.1%.
Ordinary impurities 466
Test solution: a mixture of methanol and chloroform (1:1).
Standard solution: a mixture of methanol and chloroform (1:1).
Eluant: a mixture of n-propyl alcohol, glacial acetic acid, and water (8:1:1).
Visualization: 2.
Organic volatile impurities, Method V 467: meets the requirements.
Solvent— Use dimethyl sulfoxide.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay— Dissolve about 200 mg of Pyrimethamine, accurately weighed, in 25 mL of glacial acetic acid, warming slightly to effect solution. Cool the solution to room temperature, add 4 drops of quinaldine red TS, and titrate with 0.1 N perchloric acid VS. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 24.87 mg of C12H13ClN4.
Auxiliary Information— Staff Liaison : Behnam Davani, Ph.D., MBA, Senior Scientist
Expert Committee : (MDAA05) Monograph Development-Antivirals and Antimicrobials
USP29–NF24 Page 1872
Phone Number : 1-301-816-8394