A: It meets the requirements under Identification—Organic Nitrogenous Bases á181ñ,a volume of Injection equivalent to 100mg of verapamil hydrochloride being used,chloroform being used in place of carbon disulfide,and a 0.1-mm cell being used in place of a 1-mm cell.

B: The chromatogram of the Assay preparationobtained as directed in the Assayexhibits a major peak for verapamil hydrochloride,the retention time of which corresponds to that exhibited in the chromatogram of the Standard preparation,obtained as directed in the Assay.

C: It responds to the tests for Chloride á191ñ.

Aqueous solvent mixture ,Mobile phase,System suitability solution,and Chromatographic system—Proceed as directed for Chromatographic purityunder Verapamil Hydrochloride.

Standard solution— Dissolve accurately weighed quantities of USP Verapamil Hydrochloride RS,USP Verapamil Related Compound A RS,3,4-dimethoxybenzaldehyde,and 3,4-dimethoxybenzyl alcohol in Mobile phaseto obtain a solution having known concentrations of about 2.5mg of USP Verapamil Hydrochloride RSper mLand 0.0075mg each of USP Verapamil Related Compound A RS,3,4-dimethoxybenzaldehyde,and 3,4-dimethoxybenzyl alcohol per mL.

Test solution— Use the Assay preparation.

Procedure— Separately inject equal volumes (about 10µL)of the Standard solutionand the Test solutioninto the chromatograph,and allow the Test solutionto elute for not less than four times the retention time for verapamil hydrochloride.Record the chromatograms,and measure all of the peak responses.The retention times are about 0.4for 3,4-dimethoxybenzyl alcohol,0.5for verapamil related compound A,0.7for 3,4-dimethoxybenzaldehyde,and 1.0for verapamil.Calculate the quantity,in mg,of each individual impurity in each mLof the Injection taken by the formula: in which Cis the concentration,in mg per mL,of the appropriate impurity in the Standard solution;Lis the labeled quantity,in mg per mL,of verapamil hydrochloride in the Injection;Dis the concentration,in mg per mL,of verapamil hydrochloride in the Test solution,on the basis of the labeled quantity in each mLand the extent of dilution;and rUand rSare the peak responses of the appropriate impurity in the Test solutionand the Standard solution,respectively:not more than 0.3%of any specified impurity is found,and the sum of all impurities is not greater than 1.0%.

Aqueous solvent mixture ,Mobile phase,System suitability solution,and Chromatographic system—Proceed as directed for Chromatographic purityunder Verapamil Hydrochloride.

Standard preparation— Dissolve accurately weighed quantities of USP Verapamil Hydrochloride RSin Mobile phaseto obtain a solution having a known concentration of about 2.5mg per mL.

Assay preparation— Dilute the Injection quantitatively,if necessary,with Mobile phaseto obtain a solution having a concentration of not more than 2.5mg of verapamil hydrochloride per mL.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,and allow the Assay preparationto elute for not less than four times the retention time for verapamil.Record the chromatograms,and measure the responses for all of the major peaks.Calculate the quantity,in mg,of C27H38N2O4·HCl,in each mLof the Injection taken by the formula: in which Cis the concentration,in mg per mL,of USP Verapamil Hydrochloride RSin the Standard preparation;Lis the labeled quantity,in mg per mL,of verapamil hydrochloride in the Injection;Dis the concentration,in mg per mL,of verapamil hydrochloride in the Assay preparation,on the basis of the labeled quantity in each mLand the extent of dilution;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.