A: Place a quantity of Oral Suspension,equivalent to about 100mg of sulfamethoxazole,in a 50-mLcentrifuge tube;add 5mLof ammonium hydroxide;and shake gently.Add 25mLof methanol,shake thoroughly for 3minutes,centrifuge,decant the supernatant into a 50-mLvolumetric flask,dilute with methanol to volume,and mix.Apply 50µLof this solution and 50µLof a solution prepared by dissolving 100mg of USP Sulfamethoxazole RSin 5mLof ammonium hydroxide and diluting with methanol to 50.0mLto a suitable thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel.Allow the spots to dry,and develop the chromatogram in a solvent system consisting of a mixture of alcohol,n-heptane,chloroform,and glacial acetic acid (25:25:25:7)until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,mark the solvent front,and allow the solvent to evaporate.Locate the spots on the plate by lightly spraying with a solution prepared by dissolving 0.10g of p-dimethylaminobenzaldehyde in 1mLof hydrochloric acid and diluting with alcohol to 100mL:the RFvalue of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.

B: Transfer a quantity of Oral Suspension,equivalent to about 500mg of sulfamethoxazole,to a 50-mLcentrifuge tube;add about 25mLof water;mix;and centrifuge.Decant and discard the supernatant,resuspend the residue in 25mLof water,mix,and centrifuge again.Decant and discard the clear supernatant.Repeat the washing procedure an additional two times.Dissolve the residue in 10mLof hydrochloric acid,and add 15mLof sodium nitrite solution (1in 100)and 5mLof sodium hydroxide solution (1in 10)containing 10mg of 2-naphthol:a red-orange precipitate is produced.

FOR ORAL SUSPENSION PACKAGED IN SINGLE-UNIT CONTAINERS: meets the requirements.

FOR ORAL SUSPENSION PACKAGED IN MULTIPLE-UNIT CONTAINERS: meets the requirements.