Sulfadoxine

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

Sulfadoxine contains NLT 99.0% and NMT 101.0% of sulfadoxine (C₁₂H₁₄N₄O₄S), calculated on the dried basis.

2 IDENTIFICATION

Change to read:

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K (CN 1-May-2020)

Change to read:

B. Spectroscopic Identification Tests 〈197〉, Ultraviolet-Visible Spectroscopy: 197U (CN 1-May-2020)

Sample solution: 6 μg/mL in 0.1 N sodium hydroxide

Acceptance criteria: Meets the requirements

C. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

3 ASSAY

Procedure

Solution A: Add 1 mL of phosphoric acid to water, and dilute to 1000 mL.

Mobile phase: Acetonitrile and Solution A (17:83)

Standard solution: 0.4 mg/mL of USP Sulfadoxine RS prepared as follows. Dissolve an appropriate amount of USP Sulfadoxine RS in a suitable container with acetonitrile using 17% of the final volume, then dilute with Solution A to volume.

Sample solution: 0.4 mg/mL of sulfadoxine prepared as follows. Dissolve an appropriate amount of sulfadoxine in a suitable container with acetonitrile using 17% of the final volume, then dilute with Solution A to volume.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 230 nm

Column: 2.0-mm × 10-cm; 3-μm packing L11

Flow rate: 0.3 mL/min

Injection volume: 5 μL

System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: NMT 1.8

Relative standard deviation: NMT 1.0%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of sulfadoxine (C₁₂H₁₄N₄O₄S) in the portion of Sulfadoxine taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response from the Sample solution

r_S = peak response from the Standard solution

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

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

Acceptance criteria: 99.0%–101.0% on the dried basis

4 IMPURITIES

Residue on Ignition 〈281〉: NMT 0.1%

Organic Impurities

Diluent: Alcohol and ammonium hydroxide (9:1)

Standard solution: 0.10 mg/mL of USP Sulfadoxine RS in Diluent

Sample solution: 20 mg/mL of Sulfadoxine in Diluent

Chromatographic system

(See Chromatography 〈621〉, Thin-Layer Chromatography.)

Mode: TLC

Adsorbent: 0.25-mm layer of chromatographic silica gel

Application volume: 10 μL

Developing solvent system: Chloroform, methanol, and dimethylformamide (20:2:1)

Spray reagent A: 1-in-10 solution of sulfuric acid in alcohol

Spray reagent B: 1-in-200 solution of N-(1-naphthyl)ethylenediamine dihydrochloride in alcohol

Analysis

Samples: Standard solution and Sample solution

Separately apply the Sample solution and the Standard solution to the Adsorbent. Develop the chromatogram in the Developing solvent system until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chamber, and air dry.

Spray the dried plate with Spray reagent A, and expose to nitrous fumes generated by adding 7 M sulfuric acid dropwise to a solution containing 10% sodium nitrite and 3% potassium iodide. Dry the plate in a current of warm air for 15 min, and spray with Spray reagent

B.

Acceptance criteria: No spot in the Sample solution, other than the principal spot, is greater in size and intensity than the spot from the

Standard solution.

5 SPECIFIC TESTS

Melting Range or Temperature 〈741〉: 197°–200°

Loss on Drying 〈731〉

Analysis: Dry at 105° for 4 h.

Acceptance criteria: NMT 0.5%

6 ADDITIONAL REQUIREMENTS

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

USP Reference Standards 〈11〉

USP Sulfadoxine RS