A: Triturate a quantity of finely powdered Tablets,equivalent to about 500mg of sulfamethizole,with 5mLof chloroform,and transfer to a small filter.Wash with another 5-mLportion of chloroform,and discard the filtrate.Triturate the residue with 10mLof 6Nammonium hydroxide for 5minutes,add 10mLof water,filter,and proceed as directed in the Identificationtest under Sulfamethizole Oral Suspension,beginning with “Warm the filtrate.”

B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that of the Standard preparationas obtained in the Assay.

Medium: 0.01Nhydrochloric acid;900mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Procedure— Determine the amount of C9H10N4O2S2dissolved by employing UVabsorption at the wavelength of maximum absorbance at about 267nm on 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 Sulfamethizole RSin the same Medium.

Tolerances— Not less than 75%(Q)of the labeled amount of C9H10N4O2S2is dissolved in 30minutes.

Mobile phase ,Standard preparation,and Chromatographic system—Prepare as directed in the Assayunder Sulfamethizole.

Assay preparation— Weigh and finely powder not less than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 40mg of sulfamethizole,to a 250-mLscrew-capped bottle.Transfer 100.0mLof methanol to the bottle,cap the bottle,shake by mechanical means for 30minutes,and filter.Quantitatively dilute a portion of the filtered solution with Mobile phaseto obtain the Assay preparationhaving a concentration of about 8µg per mL.

Procedure— Separately inject equal volumes (about 50µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C9H10N4O2S2in the portion of Tablets taken by the formula: in which Cis the concentration,in µg per mL,of USP Sulfamethizole RSin the Standard preparation,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.