Medium: 0.01 N hydrochloric acid; 900 mL.

Apparatus 2: 50 rpm.

Time: 60 minutes.

Procedure— Determine the amount of total sulfapyrimidines dissolved by employing UV absorption at the wavelength of maximum absorbance at about 254 nm on filtered portions of the solution under test, suitably diluted with 0.01 N sodium hydroxide, in comparison with a Standard solution having approximately equal, known, concentrations of USP Sulfadiazine RS, USP Sulfamerazine RS, and USP Sulfamethazine RS in the same media.

Tolerances— Not less than 70% (Q) of the labeled amount of total sulfapyrimidines is dissolved in 60 minutes.

Mobile phase , Standard preparation, and Chromatographic system—Proceed as directed in the Assay under Trisulfapyrimidines Oral Suspension.

Assay preparation— Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 250 mg of total sulfapyrimidines, to a 250-mL volumetric flask, add 50 mL of 0.1 N sodium hydroxide, swirl for several minutes to dissolve the sulfapyrimidines, dilute with water to volume, and mix. Filter the mixture, discarding the first several mL of the filtrate. Pipet 3 mL of the clear filtrate into a 25-mL volumetric flask, dilute with water to volume, and mix.

Procedure— Proceed as directed for Procedure in the Assay under Trisulfapyrimidines Oral Suspension. Calculate the quantity, in mg, of sulfadiazine in the portion of Tablets taken by the formula: in which C is the concentration, in µg per mL, of USP Sulfadiazine RS in the Standard preparation, and RU and RS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively. Similarly measure the responses of the sulfamerazine and sulfamethazine peaks, and calculate the quantity, in mg, of each in the portion of Tablets taken.