Sulfathiazole
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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)
Sulfathiazole contains not less than 99.0 percent and not more than 100.5 percent of C9H9N3O2S2, calculated on the dried basis.
Packaging and storage—Preserve in well-closed, light-resistant containers.
USP REFERENCE STANDARDS 〈11〉—
USP Sulfathiazole RS
Identification—
Change to read:
A: Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy : 197K (CN 1-May-2020) .
B: To 100 mg add 5 mL of 3 N hydrochloric acid, 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 an 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, Class I 〈741〉: between 200° and 204°.
Acidity—Digest 2 g with 100 mL of water at about 70° for 5 minutes, cool at once to about 20°, and filter. Titrate 25 mL of the filtrate with 0.10 N sodium hydroxide, using 2 drops of phenolphthalein TS as the indicator: not more than 0.5 mL is required to produce a pink color. (Retain the remainder of the filtrate for the tests for Chloride 〈221〉 and for Sulfate 〈221〉.)
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%.
CHLORIDE 〈221〉—A 25-mL portion of the filtrate prepared as directed in the test for Acidity shows no more chloride than corresponds to 0.10 mL of 0.020 N hydrochloric acid (0.014%).
SULFATE 〈221〉—A 25-mL portion of the filtrate prepared as directed in the test for Acidity shows no more sulfate than corresponds to 0.2 mL of 0.02 N sulfuric acid (0.04%). ORDINARY IMPURITIES 〈466〉—
Test solution: methanol.
Standard solution: methanol.
Eluant: a mixture of 1-propanol and 1 N ammonium hydroxide (22:3). Visualization: 1.
Assay—Proceed with Sulfathiazole as directed under Nitrite Titration 〈451〉. Each mL of 0.1 M sodium nitrite is equivalent to 25.53 mg of C9H9N3O2S2 .
