Medium: 0.1Nhydrochloric acid;900mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Procedure— Determine the amount of C24H40N8O4dissolved by employing UVabsorption at the wavelength of maximum absorbance at about 282nm 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 Dipyridamole RSin the sameMedium.

Tolerances— Not less than 70%(Q)of the labeled amount of C24H40N8O4is dissolved in 30minutes.

Procedure for content uniformity— Transfer 1Tablet to a 100-mLvolumetric flask,add 50mLof 1Nhydrochloric acid,heat in a steam bath for 5minutes,and shake by mechanical means for 30minutes.Cool to room temperature,dilute with 1Nhydrochloric acid to volume,and mix.Filter,discarding the first 25mLof the filtrate.Dilute an accurately measured portion of the subsequent filtrate with 1Nhydrochloric acid to provide a solution containing about 10µg of dipyridamole per mL.Concomitantly determine the absorbances of this solution and of a solution of USP Dipyridamole RSin the same medium having a known concentration of about 10µg per mL,in 1-cm cells at the wavelength of maximum absorbance at about 282nm using 1Nhydrochloric acid as the blank.Calculate the quantity,in mg,of C24H40N8O4in the Tablet taken by the formula: in which Tis the labeled quantity,in mg,of dipyridamole in the Tablet;Cis the concentration,in µg per mL,of USP Dipyridamole RSin the Standard solution;Dis the concentration,in µg per mL,of dipyridamole in the solution from the Tablet based upon the labeled quantity per Tablet and the extent of dilution;and AUand ASare the absorbances of the solution from the Tablet and the Standard solution,respectively.

Mobile phase— Dissolve 250mg of dibasic sodium phosphate in 250mLof water,and adjust with dilute phosphoric acid (1in 3)to a pHof 4.6.Add 750mLof methanol,mix,filter through a 0.5-µm membrane filter,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Using an accurately weighed quantity of USP Dipyridamole RS,prepare a solution in Mobile phasehaving a known concentration of about 15µg per mL.

Assay preparation— Transfer not less than 20Tablets to a 1000-mLvolumetric flask,add 100mLof water,and sonicate for 15minutes.Add about 750mLof methanol,and shake by mechanical means for 30minutes.Dilute with methanol to volume,mix,and centrifuge.Dilute an accurately measured volume (VSmL)of the clear supernatant quantitatively with Mobile phaseto obtain a solution (VAmL)containing about 15µg of dipyridamole per mL.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 288-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency determined from the analyte peak is not less than 1000theoretical plates,the tailing factor for the analyte peak 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 50µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C24H40N8O4in the Tablets taken by the formula: in which Cis the concentration,in µg per mL,of USP Dipyridamole RSin the Standard preparation;VAis the volume,in mL,of the Assay preparation;VSis the volume,in mL,of supernatant taken for the Assay preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.