Medium: 0.1Nhydrochloric acid;900mL.

Apparatus 2: 50rpm.

Time: 30minutes.

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

Procedure— Inject a volume of a filtered portion of the solution under test into the chromatograph,record the chromatogram,and measure the response for the major peak.Calculate the quantity of C21H31N3O5dissolved in comparison with a Standard solution having a known concentration of USP Lisinopril RSin the same medium and similarly chromatographed.

Tolerances— Not less than 80%(Q)of the labeled amount of C21H31N3O5in the Tablets is dissolved in 30minutes.

Procedure for content uniformity—

Phosphate solution ,Mobile phase,and Chromatographic system—Prepare as directed in the Assay.

Diluent— Dissolve 2.72g of monobasic potassium phosphate in 800mLof water,adjust with phosphoric acid to a pHof 4.0,dilute with water to 1000mL,and mix.

Standard preparation— Dissolve an accurately weighed quantity of USP Lisinopril RSin Diluentto obtain a solution having a known concentration of about 0.2mg per mL.

Test preparation— Place one Tablet in a volumetric flask of appropriate size,based on the labeled quantity,in mg,of lisinopril in the Tablet,to obtain a solution containing 0.2mg of lisinopril per mL.Fill the flask to about 50%volume with Diluent,sonicate for 5minutes,and shake by mechanical means for 20minutes.Dilute with Diluentto volume,mix,and filter.

Procedure— [NOTE—Use peak areas where peak responses are indicated.]Separately inject equal volumes (about 20µL)of the Test preparationand the Standard preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C21H31N3O5in the Tablet taken by the formula: in which Tis the labeled quantity,in mg,of lisinopril in the Tablet,Cis the concentration,in mg per mL,calculated on the anhydrous basis,of USP Lisinopril RSin the Standard preparation,Dis the concentration,in mg per mL,of lisinopril in the Test preparation,based upon the labeled quantity per Tablet and the extent of dilution,and rUand rSare the lisinopril peak responses obtained from the Test preparationand the Standard preparation,respectively.

Phosphate solution ,Mobile phase,Diluent,and Chromatographic system—Prepare as directed in the Assay.

Standard solution— Dilute the Standard preparation,prepared as directed in the Assay,with Diluentto obtain a solution having a known concentration of about 20µg per mL.

Test solution— Use the Assay preparation.

Procedure— Proceed as directed in the Assay.Measure the responses of the lisinopril peak obtained from the Standard solution,and of all peaks other than that of lisinopril obtained from the Test solution.Calculate the percentage of related compounds in each Tablet taken by the formula: in which Vis the volume,in mL,of the Test solution;Cis the concentration,in mg per mL,calculated on the anhydrous basis,of USP Lisinopril RSin the Standard solution;Lis the quantity,in mg,of lisinopril in each Tablet,taken as determined in the Assay;rUis the sum of all peak responses other than that of lisinopril obtained from the Test solution;and rSis the lisinopril peak response obtained from the Standard solution:not more than 2.0%,calculated on the basis of the quantity,in mg,of lisinopril in the portion of Tablets taken,as determined in the Assay,is found.

Phosphate solution— Dissolve 4.1g of monobasic potassium phosphate in about 900mLof water in a 1000-mLvolumetric flask,and adjust with phosphoric acid to a pHof 2.0.Dilute with water to volume,and mix.

Mobile phase— Dissolve 1.0g of sodium 1-hexanesulfonate in 800mLof Phosphate solution.Add 200mLof acetonitrile,mix,filter,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Diluent— Prepare a mixture of water and methanol (4:1).

Standard preparation— Dissolve an accurately weighed quantity of USP Lisinopril RSin Diluentto obtain a solution having a known concentration of about 0.2mg per mL.

Assay preparation— Transfer to a suitable size volumetric flask 10Tablets,which when diluted with Diluentwill yield a solution having a concentration of about 0.2mg per mL.Add Diluent,and sonicate for 5minutes.Shake the flask by mechanical means for 20minutes,dilute with Diluentto volume,mix,and filter.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 215-nm detector and a 4.6-mm ×20-cm column that contains packing L7and is maintained at a temperature of 40.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed under Procedure:the column efficiency determined from the analyte peak is not less than 850theoretical plates,the tailing factor for the analyte peak is not more than 2.0,the capacity factor,k¢,for the analyte peak is not less than 2.0,and relative standard deviation for replicate injections is not more than 2.0%.

Procedure— [NOTE—Use peak areas where peak responses are indicated.]Separately inject equal volumes (about 20µL)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 C21H31N3O5in each Tablet taken by the formula: in which Lis the labeled quantity,in mg,of lisinopril in each Tablet,Dis the concentration,in mg per mL,of lisinopril in the Assay preparationbased on the labeled quantity per Tablet and the extent of dilution,Cis the concentration,in mg per mL,calculated on the anhydrous basis,of USP Lisinopril RSin the Standard preparation,and rUand rSare the lisinopril peak responses obtained from the Assay preparationand the Standard preparation,respectively.