A: Infrared Absorption á197Kñ.

B: Ultraviolet Absorption á197Uñ—

Solvent— Use dimethyl sulfoxide.

Buffer solution— Dissolve 1.80g of anhydrous sodium acetate in 1liter of water.Adjust,if necessary,with glacial acetic acid to a pHof 4.5±0.2.

Mobile phase— Prepare a filtered and degassed mixture of Buffer solutionand acetonitrile (86:14).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve about 20mg of USP Methazolamide RS,accurately weighed,in 20mLof acetonitrile contained in a 200-mLvolumetric flask.Dilute with Buffer solutionto volume,and mix.Quantitatively dilute an accurately measured volume of this solution with Buffer solutionto obtain a solution having a known concentration of about 50µg of USP Methazolamide RSper mL.

Resolution solution— Prepare a solution of acetaminophen and USP Methazolamide RSin acetonitrile containing 0.3mg of acetaminophen and 0.5mg of methazolamide per mL.Quantitatively dilute an accurately measured volume of this solution with Buffer solutionto obtain a solution containing 30µg of acetaminophen and 50µg of methazolamide per mL.

Assay preparation— Transfer about 100mg of Methazolamide,accurately weighed,to a 200-mLvolumetric flask,dissolve in 20mLof acetonitrile,dilute with Buffer solutionto volume,and mix.Quantitatively dilute an accurately measured volume of this solution with Buffer solutionto obtain a solution having a known concentration of about 50µg per mL.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 265-nm detector and a 3.9-mm ×15.0-cm column containing packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Resolution solution,and record the peak responses as directed for Procedure:the relative retention times are about 0.6for acetaminophen and 1.0for methazolamide,the resolution,R,between the acetaminophen peak and the methazolamide peak is not less than 4.0,and the tailing factor is not more than 2.0.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative standard deviation for replicate injections is not more than 2%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the areas of the responses for the major peaks.Calculate the quantity,in mg,of C5H8N4O3S2in the portion of Methazolamide taken by the formula: in which Cis the concentration,in µg per mL,of USP Methazolamide RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.