A: Transfer a quantity of finely powdered Tablets, equivalent to about 100 mg of dapsone, to a suitable container, add 5 mL of acetone, shake for 5 minutes, filter, and evaporate the filtrate to dryness. Dry this residue at 105 for 1 hour: the residue so obtained responds to Identification test A under Dapsone.

B: Triturate a quantity of finely powdered Tablets, equivalent to about 100 mg of dapsone, with 50 mL of methanol, and filter. Dilute a portion of the filtrate with methanol to make approximately a 1 in 200,000 solution: this solution responds to Identification test B under Dapsone.

Medium: dilute hydrochloric acid (2 in 100); 1000 mL.

Apparatus 1: 100 rpm.

Time: 60 minutes.

Procedure— Withdraw and filter a portion of the solution under test. Transfer an accurately measured portion of the filtrate, estimated to contain about 0.2 mg of dapsone, to a 25-mL volumetric flask, add 5 mL of 1 N sodium hydroxide, dilute with water to volume, and mix. Determine the amount of C12H12N2O2S dissolved from UV absorbances at the wavelength of maximum absorbance at about 290 nm of the solutions so obtained from the solution under test in comparison with a Standard solution having a known concentration of USP Dapsone RS in the same medium.

Tolerances— Not less than 75% (Q) of the labeled amount of C12H12N2O2S is dissolved in 60 minutes.

Procedure for content uniformity— Transfer 1 Tablet to a 100-mL volumetric flask, add 2.0 mL of water, and allow to stand for 30 minutes, swirling occasionally. Add about 70 mL of methanol, and place the flask in an ultrasonic bath until the specimen is completely dispersed. Add methanol to volume, mix, and centrifuge a portion of the mixture. Quantitatively dilute an accurately measured volume of the clear supernatant with methanol to obtain a solution having a concentration of about 8 µg of dapsone per mL. Dissolve an accurately weighed quantity of USP Dapsone RS in methanol to obtain a Standard solution having a known concentration of about 8 µg per mL. Concomitantly determine the absorbances of the test solution and the Standard solution in 1-cm cells at the wavelength of maximum absorbance at about 296 nm, with a suitable spectrophotometer, using methanol as the blank. Calculate the quantity, in mg, of C12H12N2O2S in the Tablet taken by the formula: in which T is the labeled quantity, in mg, of dapsone in the Tablet, C is the concentration, in µg per mL, of USP Dapsone RS in the Standard solution, D is the concentration, in µg per mL, of dapsone in the solution from the Tablet, based upon the labeled quantity per Tablet and the extent of dilution, and AU and AS are the absorbances of the solution from the Tablet and the Standard solution, respectively.

(Official January 1, 2007)

Mobile phase, Standard preparation, and Chromatographic system— Prepare as directed in the Assay under Dapsone.

Assay preparation— Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 50 mg of dapsone, to a 200-mL volumetric flask. Add 150 mL of methanol, and place the flask in an ultrasonic bath at a temperature of 35 for 15 minutes, with occasional shaking. Allow to cool to room temperature, add methanol to volume, and mix. Centrifuge a portion of the mixture until clear. Transfer 5.0 mL of the clear supernatant to a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix.

Procedure— Proceed as directed for Procedure in the Assay under Dapsone. Calculate the quantity, in mg, of C12H12N2O2S in the portion of Tablets taken by the formula: