Medium: 0.1Nhydrochloric acid;900mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Octylamine buffer— Proceed as directed in the Assay.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and Octylamine buffer(13:7).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Test solution— Use a filtered portion of the solution under test from the dissolution vessel.

Standard solution— Dissolve an accurately weighed amount of USP Benztropine Mesylate RSin Dissolution Medium,and dilute quantitatively,and stepwise if necessary,with Dissolution Medium to obtain a solution having a known concentration similar to that of the Test solution.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 220-nm detector and a 4.6-mm ×25-cm column that contains packing L7.The flow rate is about 2mLper minute.Chromatograph the Standard solution,and record the peak responses as directed for Procedure:the tailing factor is not more than 2.0;and the relative standard deviation for replicate injections is not more than 3.0%.

Procedure— Separately inject equal volumes (about 300µL)of the Standard solutionand a filtered portion of the solution under test into the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C21H25NO·CH4O3Sdissolved by the formula: in which Cis the concentration,in mg per mL,of USP Benztropine Mesylate RSin the Standard solution;and rUand rSare the peak responses obtained from the solution under test and the Standard solution,respectively.

Tolerances— Not less than 80%(Q)of the labeled amount of C21H25NO·CH4O3Sis dissolved in 30minutes.

Octylamine buffer— Transfer about 0.83mLof octylamine to a 1-Lvolumetric flask,dilute with water to volume,mix,and adjust with phosphoric acid to a pHof 3.0.

Diluting solution— Prepare a mixture of water,isopropyl alcohol,and phosphoric acid (60:40:0.1).

Mobile phase— Prepare a filtered and degassed mixture of Octylamine bufferand acetonitrile (11:9).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Benztropine Mesylate RSin Diluting solution,and dilute quantitatively,and stepwise if necessary,with Diluting solutionto obtain a solution having a known concentration of about 0.04mg per mL.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 10mg of benztropine mesylate,to a 250-mLvolumetric flask,and add 150mLof Diluting solution.Mix by mechanical means for not less than 60minutes,and dilute with Diluting solutionto volume.Centrifuge a portion of this mixture,and filter the supernatant layer.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 259-nm detector and a 4.6-mm ×25-cm column that contains packing L7.The flow rate is about 0.7mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the tailing factor is not more than 4.0;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 benztropine mesylate (C21H25NO·CH4O3S)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Benztropine Mesylate RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.