Dapsone

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

Dapsone contains NLT 98.0% and NMT 102.0% of dapsone (C₁₂H₁₂N₂O₂S), calculated on the dried basis.

2 IDENTIFICATION

A. SPECTROSCOPIC IDENTIFICATION TESTS (197), Infrared Spectroscopy: 197K

B. 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

Change to read:

3.1 PROCEDURE

Mobile phase: Transfer 100 mL of isopropyl alcohol, 100 mL of acetonitrile, and 100 mL of ethyl acetate to a 1000-mL volumetric flask. Add hexane to volume without mixing, then mix, and allow the mixture to cool to room temperature.

Standard solution: 25 µg/mL of USP Dapsone RS in Mobile phase

Sample solution: 25 µg/mL of Dapsone in Mobile phase

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 254 nm

Column: 4-mm x 30-cm; 10-µm packing 13

Flow rate: 1 mL/min

Injection volume: 10 µL

Run time: ▲NLT▲ (USP 1-Dec-2021) 2 times the retention time of dapsone

System suitability

Suitability requirements

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of dapsone (C₁₂H₁₂N₂O₂S) in the portion of Dapsone taken: 

Result = (r_u/r_s) × (C_s/C_u) × 100

r_u = peak response of dapsone from the Sample solution

r_s = peak response of dapsone from the Standard solution s

C_s = concentration of USP Dapsone RS in the Standard solution (µg/mL)

C_u = concentration of Dapsone in the Sample solution (µg/mL)

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

4 IMPURITIES

4.1 RESIDUE ON IGNITION (281): NMT 0.1%

Delete the following:

4.2 SELENIUM (291)

Sample: 100-mg sample mixed with 100 mg of magnesium oxide

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

4.3 ORGANIC IMPURITIES

Standard solution A: 12.5 mg/mL of USP Dapsone RS in methanol

Standard solution B: 62.5 µg/mL of USP Dapsone RS in methanol from Standard solution A

Sample solution: 12.5 mg/mL of Dapsone in methanol

Chromatographic system

(See Chromatography (621), General Procedures, Thin-Layer Chromatography.)

Mode: TLC

Adsorbent: 150- to 200-µm layer of chromatographic silica gel

Application volume: 4 µL

Developing solvent system: Acetone, chloroform, n-butyl alcohol, and formic acid (15:60:15:10). Prepare the solvent system fresh daily.

Equilibrate the chromatographic chamber with the solvent system for 30 min prior to developing the chromatographic plate.

Spray reagent: 0.1% (w/v) solution of 4-dimethylaminocinnamaldehyde in glacial acetic acid and water (1:1)

Analysis

Samples: Standard solution A, Standard solution B, and Sample solution

Position the plate in a chromatographic chamber, and develop the chromatograms 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 developing chamber and air-dry. Spray the plate lightly with Spray reagent. Examine the spots that are developed immediately, and compare the intensities of any secondary spots observed in the Sample solution with those of the principal spots of the Standard solutions.

Acceptance criteria: No secondary spot from the chromatogram of the Sample solution is larger or more intense than the principal spot of Standard solution B (0.5%), and the sum of the intensities of all the secondary spots of the Sample solution corresponds to NMT 1.0%.

5 SPECIFIC TESTS

5.1 LOSS ON DRYING (731).

Analysis: Dry at 105° for 3 h.

Acceptance criteria: NMT 1.5%

6 ADDITIONAL REQUIREMENTS

6.1 PACKAGING AND STORAGE: Preserve in well-closed, light-resistant containers.

6.2 USP REFERENCE STANDARDS (11)

USP Dapsone RS