A: Infrared Absorption á197Kñ.

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.

C: Dissolve 0.10g in 2mLof alcohol,and add 1mLof 2Nnitric acid and 3drops of silver nitrate TS:a white precipitate is formed,and it dissolves on the dropwise addition of ammonium hydroxide.

Mobile phase,System suitability solution,Standard preparation,andChromatographic system— Proceed as directed in the Assay.

Standard solution— Dissolve accurately weighed quantities of USP Imipramine Hydrochloride RSand USP Iminodibenzyl RSin acetonitrile,and dilute with a mixture of water and acetonitrile (5:3)to obtain a solution having known concentrations of about 2.5µg of each component per mL.

Test solution— Transfer about 63mg of Imipramine Hydrochloride,accurately weighed,to a 50-mLvolumetric flask,dissolve in and dilute with a mixture of water and acetonitrile (5:3),and mix.

Procedure— Separately inject equal volumes (about 20µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the peak responses.The relative retention times are about 0.8for N-(dimethylaminopropyl)iminostilbene and 1.0for imipramine.Calculate the percentage of iminodibenzyl in the portion of Imipramine Hydrochloride taken by the formula: in which Cis the concentration,in µg per mL,of USP Iminodibenzyl RSin the Standard solution;Wis the weight,in mg,of Imipramine Hydrochloride taken to prepare the Test solution;and rUand rSare the iminodibenzyl peak responses obtained from the Test solutionand the Standard solution,respectively:not more than 0.1%of iminodibenzyl is found.Calculate the percentage of each other impurity in the portion of Imipramine Hydrochloride taken by the formula: in which Cis the concentration,in µg per mL,of USP Imipramine Hydrochloride RSin the Standard solution;Wis the weight,in mg,of Imipramine Hydrochloride taken to prepare the Test solution;riis the peak response of each individual impurity,excluding iminodibenzyl,obtained from the Test solution,and rSis the peak response of imipramine obtained from the Standard solution:not more than 0.1%of N-(dimethylaminopropyl)iminostilbene is found;not more than 0.2%of any other impurity is found;and the total of all impurities found is not more than 1.0%.

Mobile phase— Prepare a filtered and degassed mixture of 0.06Msodium perchlorate,acetonitrile,and triethylamine (625:375:1),and adjust with perchloric acid to a pHof 2.0.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

System suitability solution— Transfer about 15mg of USP Imipramine Hydrochloride RSand about 15mg of USP Desipramine Hydrochloride RS,accurately weighed,to a 50-mLvolumetric flask,dissolve in and dilute with a mixture of water and acetonitrile (5:3)to volume,and mix.

Standard preparation— Dissolve an accurately weighed quantity of USP Imipramine Hydrochloride RSin a mixture of water and acetonitrile (5:3)to obtain a solution having a known concentration of about 0.3mg per mL.

Assay preparation— Transfer about 30mg of Imipramine Hydrochloride,accurately weighed,to a 100-mLvolumetric flask,dissolve in and dilute with a mixture of water and acetonitrile (5:3)to volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 269-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The column temperature is maintained at 40,and the flow rate is about 1.5mLper minute.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the resolution,R,between the imipramine and desipramine peaks is not less than 1.3.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative standard deviation for replicate injections is not more than 2.0%for imipramine.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the peak responses.Calculate the quantity,in mg,of C19H24N2·HCl in the portion of Imipramine Hydrochloride taken by the formula: in which Cis the concentration,in mg per mL,of USP Imipramine Hydrochloride RSin the Standard preparation;and rUand rSare the imipramine peak responses obtained from the Assay preparationand the Standard preparation,respectively.