Sulfadiazine

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION

Sulfadiazine contains NLT 98.0% and NMT 102.0% of sulfadiazine, calculated on the dried basis.

2 IDENTIFICATION

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K

B.

Sample: 50 mg

Analysis: Carefully melt the Sample in a small test tube.

Acceptance criteria: A reddish brown color develops upon melting, and the fumes evolved during decomposition do not discolor moistened lead acetate test paper (distinction from sulfathiazole).

C.

Sample: 1 g

Analysis 1: Gently heat the Sample in a small test tube until a sublimate is formed. Collect a few milligrams of the sublimate with a glass rod, and mix in a test tube with 1 mL of a solution (1 in 20) of Resorcinol in alcohol. Add 1 mL of sulfuric acid, and mix by shaking.

Acceptance criteria 1: A deep red color appears at once.

Analysis 2: Cautiously dilute the mixture obtained in Analysis 1 with 25 mL of ice-cold water, and add an excess of 6 N ammonium hydroxide.

Acceptance criteria 2: A blue or reddish blue color is produced.

3 ASSAY

Procedure

Mobile phase: Acetonitrile, water, and glacial acetic acid (12:87:1)

Standard solution: 1 mg/mL of USP Sulfadiazine RS in 0.025 N sodium hydroxide

Sample solution: 1 mg/mL of Sulfadiazine in 0.025 N sodium hydroxide

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 254 nm

Column: 4-mm × 30-cm; packing L1

Flow rate: 2 mL/min

Injection volume: 10 μL

System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: NMT 1.5

Relative standard deviation: NMT 2.0%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of sulfadiazine in the portion of Sulfadiazine taken:

Result = (r_U/r_S) × (C_S /C_U) × 100

r_U = peak response of sulfadiazine from the Sample solution

r_S = peak response of sulfadiazine from the Standard solution

C_S = concentration of USP Sulfadiazine RS in the Standard solution (mg/mL)

C_U = concentration of Sulfadiazine in the Sample solution (mg/mL)

Acceptance criteria: 98.0%–102.0% on the dried basis

4 IMPURITIES

Residue on Ignition 〈281〉: NMT 0.1%

Delete the following:

Selenium 〈291〉

Sample: 200 mg

Acceptance criteria: NMT 30 ppm (USP 1-Dec-2021)

Ordinary Impurities 〈466〉

Diluent: Toluene and dimethylformamide (2:1)

Standard solutions: 0.008, 0.041, 0.08, and 0.17 mg/mL of USP Sulfadiazine RS in Diluent

Sample solution: 8.3 mg/mL of Sulfadiazine in Diluent

Eluant: Chloroform, methanol, and ammonium hydroxide (30:12:1)

Visualization: 11

Acceptance criteria: Meets the requirements

5 SPECIFIC TESTS

Clarity and Color of Solution

Sample: 1 g

Analysis: Dissolve the Sample in a mixture of 20 mL of water and 5 mL of 1 N sodium hydroxide.

Acceptance criteria: The solution is clear and not more deeply colored than pale yellow.

Acidity

Sample: 2 g

Analysis: Digest the Sample with 100 mL of water at about 70° for 5 min. Cool at once to room temperature, 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 to produce a pink color.

Loss on Drying 〈731〉

Analysis: Dry at 105° for 2 h.

Acceptance criteria: NMT 0.5%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed, light-resistant containers.

USP Reference Standards 〈11〉

USP Sulfadiazine RS