A:Ultraviolet Absorption á197Uñ— Transfer a portion of the contents of the Capsules,equivalent to about 0.1g of triamterene,to a 250-mLvolumetric flask.Add 100mLof methoxyethanol,shake until dissolved,dilute with water to volume,and mix.Transfer 5mLof this solution to a 200-mLvolumetric flask,add 5mLof formic acid,and dilute with water to volume.Prepare a solution of USP Triamterene RSin the manner described above to obtain a Standard solution with a final concentration of about 10µg per mL.Determine the UVspectrum from 280nm to 420nm.

B: The retention time of the major peak in the chromatogram of theAssay preparation corresponds to that in the chromatogram of theStandard preparation,as obtained in theAssay.

TEST1—

TEST2— If the product complies with this test,the labeling indicates that it meets USPDissolution Test 2.

Buffer solutionand Mobile phase— Proceed as directed in theAssayunderTriamterene and Hydrochlorothiazide Tablets.

Standard preparation— Transfer about 50mg of USP Triamterene RS,accurately weighed,to a 100-mLvolumetric flask.Add 10mLof acetonitrile,10mLof water,and 5mLof glacial acetic acid,sonicating for 3minutes after each addition.Cool to room temperature,dilute with water to volume,and mix.

Assay preparation— Remove,as completely as possible,the contents of 20Capsules,combine the contents,and transfer an accurately weighed portion of powder,equivalent to about that which is in one dosage unit,to a 100-mLvolumetric flask(Flask 1).To a separate 100-mLvolumetric flask,add all 20capsule shells(Flask 2).For each flask,add 10mLof acetonitrile,and sonicate for 10minutes.Add 10mLof boiling water,sonicate for 5minutes,and mix.Add 10mLof glacial acetic acid,sonicate for 10minutes,and mix.Add 60mLof water,mix,and allow to cool to room temperature.Dilute the contents ofFlask 2with water to volume,and add 5.0mLof the solution fromFlask 2toFlask 1.Dilute the contents ofFlask 1with water to volume,and mix.If necessary,quantitatively dilute with a solution of acetonitrile,glacial acetic acid,and water (10:10:80)to obtain a final concentration of about 0.5mg per mL.Filter a portion of this solution,discarding the first 3mLof the filtrate.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 280-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 1mLper minute.Chromatograph theStandard preparation,and record the peak responses as directed forProcedure:the tailing factor is not more than 2.0;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of theStandard preparationand theAssay preparationinto the chromatograph,record the chromatograms,and measure the responses of the major peaks.Calculate the quantity,in mg,of triamterene (C12H11N7)in the portion of Capsules taken by the formula: in which Cis the concentration,in mg per mL,of USP Triamterene RSin theStandard preparation;Vis the sample dilution volume,in mL,considering the 100-mLvolume of the solution inFlask 1and any subsequent dilution factor,if used;and rUand rSare the peak responses obtained from theAssay preparationand theStandard preparation,respectively.