» Sulfamethazine contains not less than 99.0 percent and not more than 100.5 percent of C12H14N4O2S, calculated on the dried basis.
Packaging and storage Preserve in well-closed, light-resistant containers.
Clarity and color of solution Dissolve 1.0 g in a mixture of 20 mL of water and 5 mL of 1 N sodium hydroxide: the solution is clear and not more deeply colored than pale yellow.
B: To 0.10 g add 10 mL of water and just sufficient sodium hydroxide solution (1 in 250) to give a faint pink spot on phenolphthalein paper. Add 5 drops of cupric sulfate TS: a yellow-green precipitate is formed, and it becomes brown on standing.
Melting range 741: between 197 and 200.
Acidity Digest 3.0 g with 150 mL of carbon dioxide-free water at 70 for about 5 minutes, stirring occasionally to maintain suspension of the test specimen. Cool the mixture rapidly in an ice bath to 20 ± 0.5, with mechanical stirring. Filter immediately, with vacuum, omitting washing of the solid but drying it thoroughly by suction. Add 2 drops of thymolphthalein TS to 25.0 mL of the filtrate, and titrate with 0.1 N sodium hydroxide VS. To a second 25.0-mL portion of the filtrate add 10 mL of hydrochloric acid. Cool the mixture to 15, and titrate with 0.1 M sodium nitrite VS as directed under Nitrite Titration 451: the volume of 0.1 N sodium hydroxide consumed does not exceed the volume of 0.1 M sodium nitrite consumed by more than 0.5 mL.
Loss on drying 731 Dry about 1 g, accurately weighed, at 105 for 2 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.1%.
Selenium 291: 0.003%, a 200-mg test specimen being used.
Heavy metals, Method II 231: 0.002%.
Ordinary impurities 466
Test solution: acetone.
Standard solution: acetone.
Eluant: a mixture of ethyl acetate, methanol, and ammonium hydroxide (17:6:5).
Assay Proceed with Sulfamethazine as directed under Nitrite Titration 451. Each mL of 0.1 M sodium nitrite is equivalent to 27.83 mg of C12H14N4O2S.
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USP32NF27 Page 3624