A: 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.

B: Transfer a volume of Injection,equivalent to about 50mg of inamrinone,to a glass-stoppered container.Add about 2g of 50-to 100-mesh sulfonic acid cation-exchange resin,and shake for about 2minutes or until the supernatant becomes essentially colorless.Filter,and collect the filtrate in an arsine generator flask (see Apparatusunder Arsenic á211ñ).Add 5mLof diluted sulfuric acid,and boil gently on a hot plate for 5to 10minutes.Cool to room temperature.Add 10mLof potassium permanganate TS,attach the scrubber unit and absorber tube,and place the apparatus on a warm hot plate.Add 1mLof indicator solution (freshly prepared by dissolving 250mg of sodium nitroferricyanide in sufficient water to make 9mLand mixing with 1mLof morpholine)to the absorber tube.Heat gently,allowing the vapors to bubble through the indicator:the indicator turns blue within 5minutes (presence of lactate).

Ion-exchange column— Place a small pledget of glass wool at the bottom of a 100-×6-mm glass column,equipped with a stopcock and a 25-mLreservoir.Soak a suitable quantity of 50-to 100-mesh sulfonic acid cation-exchange resin in 6Nhydrochloric acid for several minutes.Wash with water until the wash is neutral to wide-range pHindicator paper.Fill the column with the prepared resin to the base of the reservoir.Wash the column with about 50mLof water in several portions,draining each wash to the top of the resin before adding the next portion.Discard the washes.

Procedure— Place a 125-mLconical flask below the Ion-exchange column.Pipet a volume of Injection,equivalent to about 50mg of inamrinone,onto the column.Allow the specimen to pass through the column at the rate of about 0.5mLto 1mLper minute,draining the specimen to the top of the column and collecting the eluate in the flask.Wash the column with five 5-mLportions of water,collecting the washings in the flask.Add several small glass beads to the solution in the flask,and boil on a hot plate for about 10minutes.Add 10.0mLof 0.1Nsodium hydroxide,and boil for 20minutes.Add phenolphthalein TS,and titrate the warm solution with 0.1Nhydrochloric acid VS.Perform a blank determination (see Residual Titrationsunder Titrimetry á541ñ).Each mLof 0.1Nhydrochloric acid is equivalent to 9.008mg of C3H6O3:the lactic acid content is between 5.0and 7.5mg per mLof Injection.

Mobile phase— Dilute 11.4mLof phosphoric acid with water to 990mL.Prepare a filtered and degassed mixture of the dilute phosphoric acid and acetonitrile (99:1).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard solution— Transfer accurately weighed quantities of about 10mg of USP Inamrinone RSand about 25mg of USP Inamrinone Related Compound B RSto a 100-mLvolumetric flask,add about 60mLof lactic acid solution (1in 85),and sonicate for about 2minutes to effect solution.Cool,dilute with lactic acid solution (1in 85)to volume,and mix.Pipet 10.0mLof this solution into a 250-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Test solution— Immediately before use,pipet a volume of Injection,equivalent to about 100mg of inamrinone,into a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 313-nm detector and a 4-mm ×15-cm column that contains base-deactivated packing L7.The column temperature is maintained at a temperature between 30and 35,and the flow rate is about 2mLper minute.Chromatograph the Standard solution,and record the peak responses as directed for Procedure:the resolution,R,between inamrinone and inamrinone related compound Bis not less than 10;and the relative standard deviation for replicate injections is not more than 10%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the areas of the peak responses.Calculate the percentage of inamrinone related compound Brelative to inamrinone in the volume of Injection taken by the formula: in which Cis the concentration,in µg per mL,of USP Inamrinone Related Compound B RSin the Standard solution;Wis the weight,in mg,of inamrinone in the volume of Injection taken;and rUand rSare the inamrinone related compound Bpeak responses obtained from the Test solutionand the Standard solution,respectively.Separately calculate the percentage of any other impurity present in the volume of Injection taken by the formula: in which riis the peak response for each impurity,and the other terms are as previously defined.Not more than 2.0%of inamrinone related compound Band not more than 0.5%of any other individual impurity is found,and the sum of all impurities is not more than 3.0%.

pH7sodium borate buffer ,0.5M—Transfer 31g of boric acid to a beaker containing approximately 800mLof water.Slowly add sodium hydroxide solution (1in 5)in small quantities,stirring well after each addition,until all of the boric acid is dissolved and the pHis constant at 7.0±0.3.Transfer this solution to a 1000-mLvolumetric flask,dilute with water to volume,and mix.

Mobile phase— Prepare a filtered and degassed mixture of water,methanol,and pH7sodium borate buffer,0.5M(500:480:20).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

System suitability solution— Dissolve accurately weighed quantities of USP Inamrinone RSand USP Inamrinone Related Compound C RSin Mobile phaseto obtain a solution containing about 50µg of each per mL.

Standard preparation— Dissolve an accurately weighed quantity of USP Inamrinone RSin Mobile phase,and dilute quantitatively,and stepwise if necessary,with Mobile phaseto obtain a solution having a known concentration of about 50µg per mL.

Assay preparation— Transfer an accurately measured volume of Injection,equivalent to about 5mg of inamrinone,to a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 1mLper minute.Chromatograph the System suitability solutionand the Standard preparation,and record the peak responses as directed for Procedure:the relative retention times are 0.6for inamrinone related compound Cand 1.0for inamrinone;the resolution,R,between the inamrinone related compound Cand inamrinone peaks is not less than 3;and the relative standard deviation for replicate injections of the Standard preparationis not more than 2.0%.

Procedure— 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 amrinone (C10H9N3O)in each mLof the Injection taken by the formula: in which Cis the concentration,in µg per mL,of USP Inamrinone RSin the Standard preparation;Vis the volume,in mL,of Injection taken;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.