Medium: 0.01Nhydrochloric acid;900mL.

Apparatus 1: 100rpm.

Time: 60minutes.

Procedure— Determine the amount of C4H6N4O3S2dissolved by employing UVabsorption at the wavelength of maximum absorbance at about 265nm on filtered portions of the solution under test,suitably diluted with Medium,if necessary,in comparison with a Standard solution having a known concentration of USP Acetazolamide RSin the same Medium.

Tolerances— Not less than 75%(Q)of the labeled amount of C4H6N4O3S2is dissolved in 60minutes.

Mobile phase— Dissolve 4.1g of anhydrous sodium acetate in 950mLof water,add 20mLof methanol and 30mLof acetonitrile,and mix.Adjust with glacial acetic acid to a pHof 4.0±0.05.Filter and degas the solution.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard acetazolamide stock solution— Transfer about 25mg of USP Acetazolamide RS,accurately weighed,to a 25-mLvolumetric flask,add 2.5mLof 0.5Nsodium hydroxide,and mix to dissolve.Dilute with water to volume,and mix.

Internal standard solution— Transfer about 100mg of sulfadiazine to a 100-mLvolumetric flask,add 10mLof 0.5Nsodium hydroxide,and mix to dissolve.Dilute with water to volume,and mix.

Standard preparation— Transfer 10.0mLof Standard acetazolamide stock solutionand 10.0mLof Internal standard solutionto a 100-mLvolumetric flask,add 10mLof 0.5Nsodium hydroxide,dilute with water to volume,and mix to obtain a solution having a known concentration of about 0.1mg of USP Acetazolamide RSper mL.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 100mg of acetazolamide,to a 100-mLvolumetric flask,add 10mLof 0.5Nsodium hydroxide,and sonicate for 5minutes.Cool to room temperature,dilute with water to volume,and mix.Filter a portion of this solution,discarding the first 20mLof the filtrate.Transfer 10.0mLof the clear filtrate to a 100-mLvolumetric flask,add 10.0mLof Internal standard solutionand 10mLof 0.5Nsodium hydroxide,dilute with water to volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 2mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the resolution,R,between the analyte and internal standard peaks is not less than 2.0;and the relative standard deviation of the ratios of the analyte peak response to the internal standard peak response for replicate injections is not more than 1.0%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.The relative retention times are about 0.7for acetazolamide and 1.0for sulfadiazine.Calculate the quantity,in mg,of acetazolamide (C4H6N4O3S2)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Acetazolamide RSin the Standard preparation;and RUand RSare the peak response ratios of the analyte peak to the internal standard peak obtained from the Assay preparationand the Standard preparation,respectively.