A: Tablets respond to Identificationtest Aunder Diltiazem Hydrochloride Extended-Release Capsules.

B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

Medium: water;900mL.

Apparatus 2: 75rpm.

Times: 30minutes and 3hours.

Procedure— Determine the amount of C22H26N2O4S·HCl dissolved from UVabsorbances at the wavelength of maximum absorbance at about 240nm using filtered portions of the solution under test,suitably diluted with water,if necessary,in comparison with a Standard solution having a known concentration of USP Diltiazem Hydrochloride RSin the same Medium.

Tolerances— Use the following acceptance criteria for the 30-minute time point:at S1no unit is more than Q;at S2the average value is equal to or less than Q,and no unit is greater than Q+10%;at S3the average value is equal to or less than Q,and not more than 2units are more than Q+10%,and no unit is more than Q+25%.Use the criteria in the Acceptance Tableunder Dissolution á711ñfor the 3-hour time point.Not more than 60%(Q)of the labeled amount of C22H26N2O4S·HCl is dissolved in 30minutes,and not less than 75%(Q)is dissolved in 3hours.

Buffer,Mobile phase,Standard preparation,System suitability preparation,Chromatographic system,and Procedure— Proceed as directed in the Assayunder Diltiazem Hydrochloride.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 600mg of diltiazem hydrochloride to a 500-mLvolumetric flask.Add 200mLof methanol,sonicate for 1hour,cool,dilute with methanol to volume,and mix.Centrifuge a 25-mLaliquot at 3500rpm for 15minutes,and use the clear supernatant for injection into the liquid chromatograph.

Procedure— Calculate the quantity,in mg,of C22H26N2O4S·HCl in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Diltiazem Hydrochloride RSin the Standard preparation;and rUand rSare the diltiazem hydrochloride peak areas in the Assay preparationand the Standard preparation,respectively.