Medium: water;900mL.

Apparatus 2: 50rpm.

Time: 60minutes.

Procedure— [NOTE—Conduct the analysis of the specimen promptly after the specimen aliquot is withdrawn from the vessel,to minimize hydrolysis.]Determine the amount of C8H8Cl3N3O4S2dissolved,employing the procedure set forth in the Assay,making any necessary volumetric adjustments.

Tolerances— Not less than 65%(Q)of the labeled amount of C8H8Cl3N3O4S2is dissolved in 60minutes.

Mobile phase and Chromatographic system—Prepare as directed in the Assayunder Trichlormethiazide.

Acidic methanol— Add 2.8mLof sulfuric acid to 100mLof water,mix,and cool.Dilute with methanol to 1000mL,and mix.

Internal standard solution— Transfer about 20mg of methylparaben to a 200-mLvolumetric flask,add Acidic methanolto volume,and mix.

Standard preparation— Transfer about 20mg of USP Trichlormethiazide RS,accurately weighed,to a 50-mLvolumetric flask,add Acidic methanolto volume,and mix.Transfer 5.0mLof this solution to a centrifuge tube,add 5.0mLof Internal standard solution,and mix to obtain a solution having a known concentration of about 0.2mg of USP Trichlormethiazide RSper mL.

Assay preparation— Weigh and finely powder not less than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to 2mg of trichlormethiazide,to a centrifuge tube.Add 5.0mLof Acidic methanoland 5.0mLof Internal standard solution,and mix to disperse the powder.Insert the stopper in the tube,rotate by mechanical means for 20minutes,and centrifuge to obtain a clear supernatant.

Procedure— Separately inject equal volumes (5µLto 25µL)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 0.58for trichlormethiazide and 1.0for methylparaben.Calculate the quantity,in mg,of C8H8Cl3N3O4S2in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Trichlormethiazide RSin the Standard preparation,and RUand RSare the peak response ratios obtained from the Assay preparationand the Standard preparation,respectively.