Packaging and storage— Preserve in tight,light-resistant containers.

USP Reference standards á11ñ— USP Sulfamethizole RS.

Identification— Place a quantity of Oral Suspension,equivalent to about 500mg of sulfamethizole,in a 50-mLcentrifuge tube;add about 30mLof water;mix;and centrifuge the mixture.Decant and discard the supernatant.Resuspend the residue in 15mLof water,mix,and centrifuge the mixture.Decant and discard the clear supernatant.Repeat the washing procedure an additional two times.Dissolve the residue in a mixture of 10mLof 6Nammonium hydroxide and 10mLof water,and filter.Warm the filtrate until most of the ammonia is expelled,cool,and add 6Nacetic acid until the mixture is distinctly acid:a precipitate of sulfamethizole is formed.Collect the precipitate on a filter,wash it well with cold water,and dry at 105for 2hours:the sulfamethizole so obtained responds to Identificationtest Aunder Sulfamethizole.

Uniformity of dosage units á905ñ—

Deliverable volume á698ñ—

Assay— Transfer an accurately measured volume of Oral Suspension,equivalent to about 500mg of sulfamethizole,to a beaker.Add 50mLof water and 20mLof hydrochloric acid,stir until dissolved,cool to 15,and slowly titrate with 0.1Msodium nitrite VS,determining the endpoint potentiometrically,using suitable electrodes.Each mLof 0.1Msodium nitrite is equivalent to 27.03mg of sulfamethizole (C9H10N4O2S2).

Expert Committee:(PA7)Pharmaceutical Analysis 7

USP28–NF23Page 1827

Phone Number:1-301-816-8394