(sul'' fa pir' i deen).
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C11H11N3O2S 249.29

Benzenesulfonamide, 4-amino-N-2-pyridinyl-.
N1-2-Pyridylsulfanilamide [144-83-2].
» Sulfapyridine contains not less than 99.0 percent and not more than 100.5 percent of C11H11N3O2S, calculated on the dried basis.
Packaging and storage— Preserve in well-closed, light-resistant containers.
USP Reference standards 11
USP Sulfapyridine RS Click to View Structure
Clarity and color of solution— A solution of 1.0 g in a mixture of 20 mL of water and 5 mL of 1 N sodium hydroxide is clear and not more deeply colored than pale yellow.
B: Add 5 mL of 3 N hydrochloric acid to about 0.1 g of Sulfapyridine, and boil gently for about 5 minutes. Cool in an ice bath, add 4 mL of sodium nitrite solution (1 in 100), dilute with water to 10 mL, and place the mixture in the ice bath for 10 minutes. To 5 mL of the cooled mixture add a solution of 50 mg of 2-naphthol in 2 mL of sodium hydroxide solution (1 in 10): an orange-red precipitate is formed, and it darkens on standing.
Melting range 741: between 190 and 193.
Acidity— Digest 2.0 g with 100 mL of water at about 70 for 5 minutes, cool at once to about 20, and filter. To 25.0 mL of the filtrate add 2 drops of phenolphthalein TS, and titrate with 0.10 N sodium hydroxide: not more than 0.20 mL is required for neutralization.
Loss on drying 731 Dry it 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.
Assay— Proceed with Sulfapyridine as directed under Nitrite Titration 451. Each mL of 0.1 N sodium nitrite is equivalent to 24.93 mg of C11H11N3O2S.
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Topic/Question Contact Expert Committee
Monograph Leonel M. Santos, Ph.D.
Senior Scientific Liaison
(SM12010) Monographs - Small Molecules 1
Reference Standards RS Technical Services
USP35–NF30 Page 4720