Sulfapyridine
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
1 DEFINITION
Sulfapyridine contains NLT 99.0% and NMT 100.5% of sulfapyridine (C11H11N2O2S), calculated on the dried basis.
2 IDENTIFICATION
A. SPECTROSCOPIC IDENTIFICATION TESTS 〈197〉 , Infrared Spectroscopy : 197K
B.
Sample solution: Add 5 mL of 3 N hydrochloric acid to 0.1 g of Sulfapyridine.
Analysis: Boil gently the Sample solution for 5 min, then 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 min. 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).
Acceptance criteria: An orange-red precipitate is formed, and it darkens on standing.
3 ASSAY
NITRITE TITRATION 〈451〉: Each mL of 0.1 N sodium nitrite is equivalent to 24.93 mg of sulfapyridine (C11H11N2O2S). Acceptance criteria: 99.0%–100.5% on the dried basis
4 IMPURITIES
RESIDUE ON IGNITION 〈281〉: NMT 0.1%
Change to read:
Selenium 〈291〉 , Procedures, Procedure 1 (CN 1-J -2023)
Sample: 200 mg Acceptance criteria: 30 ppm
5 SPECIFIC TESTS
MELTING RANGE OR TEMPERATURE 〈741〉: 190°–193°
ACIDITY
Sample: 2.0 g
Analysis: Digest the Sample with 100 mL of water at 70° for 5 min, cool at once to 20°, and filter. To 25.0 mL of the filtrate add 2 drops of phenolphthalein TS, and titrate with 0.10 N sodium hydroxide.
Acceptance criteria: NMT 0.20 mL is required for neutralization.
LOSS ON DRYING 〈731〉
Analysis: Dry at 105° for 2 h.
Acceptance criteria: NMT 0.5%
CLARITY AND COLOR OF SOLUTION
Sample solution: 1.0 g in a mixture of 20 mL of water and 5 mL of 1 N sodium hydroxide Acceptance criteria: The Sample solution is clear and not more deeply colored than pale yellow.
6 ADDITIONAL REQUIREMENTS
PACKAGING AND STORAGE: Preserve in well-closed, light-resistant containers.
USP REFERENCE STANDARDS 〈11〉
USP Sulfapyridine RS
