» Sulfamethoxazole Tablets contain not less than 95.0 percent and not more than 105.0 percent of the labeled amount of C10H11N3O3S.
Packaging and storage Preserve in well-closed, light-resistant containers.
A: Place a quantity of finely powdered Tablets, equivalent to about 100 mg of sulfamethoxazole, in a 50-mL centrifuge tube, and proceed as directed for Identification test A under Sulfamethoxazole Oral Suspension, beginning with add 5 mL of ammonium hydroxide.
B: To a portion of finely powdered Tablets, equivalent to about 100 mg of sulfamethoxazole, add 2 mL of hydrochloric acid, 3 mL of sodium nitrite solution (1 in 100), and 1 mL of sodium hydroxide solution (1 in 10) containing 10 mg of 2-naphthol: a red-orange precipitate is formed.
Medium: dilute hydrochloric acid (7 in 100); 900 mL.
Apparatus 1: 100 rpm.
Time: 30 minutes.
Procedure Determine the amount of C10H11N3O3S dissolved from UV absorbances at the wavelength of maximum absorbance at about 265 nm of filtered portions of the solution under test, suitably diluted with Dissolution Medium, if necessary, in comparison with a Standard solution having a known concentration of USP Sulfamethoxazole RS in the same medium.
Tolerances Not less than 80% (Q) of the labeled amount of C10H11N3O3S is dissolved in 30 minutes.
Uniformity of dosage units 905: meet the requirements.
Assay Weigh and finely powder not less than 20 Tablets. Weigh accurately a portion of the powder, equivalent to about 500 mg of sulfamethoxazole, dissolve in a mixture of 20 mL of glacial acetic acid and 40 mL of water, and add 15 mL of hydrochloric acid. Cool to 15, and titrate immediately with 0.1 M sodium nitrite VS, determining the endpoint potentiometrically using a calomel-platinum electrode system. Each mL of 0.1 M sodium nitrite is equivalent to 25.33 mg of C10H11N3O3S.
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USP32NF27 Page 3627