A: The retention time of the major peak in the chromatogram of theAssay preparation corresponds to that in the chromatogram of theStandard preparation,as obtained in theAssay.

B: It meets the requirements for theIdentification test underDextrose.

Phosphate buffer,Mobile phase,Standard preparation,System suitability solution,and Chromatographic system— Proceed as directed in theAssay underDobutamine Hydrochloride.

Test solution— Transfer an accurately measured portion of Dobutamine in Dextrose Injection,equivalent to about 44.6mg of dobutamine to a 100-mLvolumetric flask,dilute with water to volume,and mix.

Procedure— Inject a volume (about 20µL)of theTest solutioninto the chromatograph,record the chromatograms,and measure the peak responses.Calculate the percentage of each impurity,excluding 5-hydroxymethylfurfural from all calculations,in the portion of Dobutamine in Dextrose Injection taken by the formula: in which riis the peak response for each impurity;and rsis the sum of the responses of all of the peaks:not more than 1.0%of any individual impurity is found,and the sum of all impurities is not more than 2.0%.

Ion-exchange column— Fill an 8-mm chromatographic tube to a height of about 40mm with a 100-to 200-mesh,strongly acidic,styrene-divinylbenzene cation-exchange resin.Wash the column with about 30mLof water,discarding the eluate.[NOTE—Prepare a new column for eachTest solution andBlank solution,and use each column only once.]

Test solution— Transfer 2mLof Injection to the ion-exchange column,and collect the eluate in a 50-mLvolumetric flask.Pass 25mLof water through the column,and collect the eluate in the same volumetric flask.Dilute the eluate with water to volume,and mix.Remove the stopper from the flask,and allow the solution to stand for about 30minutes in order to oxidize any bisulfite ions present.The solution so obtained is theTest solution.

Blank solution— Prepare aBlank solution in a similar manner to theTest solution by passing 27mLof water through an ion-exchange column,and collecting the eluate in a 50-mLvolumetric flask.Dilute with water to volume,and mix.

Procedure— Determine the absorbance of theTest solution in a 1-cm cell at 284nm,with a suitable spectrophotometer,after correcting for theBlank solution:the absorbance is not more than 0.25.

1000a/l(47.96),

Phosphate buffer,Mobile phase,Standard preparation,System suitability solution,and Chromatographic system— Proceed as directed in theAssay underDobutamine Hydrochloride.

Assay preparation— Transfer an amount of Dobutamine in Dextrose Injection,equivalent to about 44.6mg of dobutamine,accurately weighed,to a 100-mLvolumetric flask,dilute with water to volume,and mix.[NOTE—Refrigerate until injected,and use within 8hours.]

Procedure— Separately inject equal volumes (about 20µL)of theStandard preparation and theAssay preparation into the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of dobutamine (C18H23NO3)in the portion of Dobutamine in Dextrose Injection taken by the formula: in which 301.39and 337.84are the molecular weights of dobutamine and dobutamine hydrochloride,respectively;Cis the concentration,in mg per mL,of USP Dobutamine Hydrochloride RSin theStandard preparation;and rUand rSare the peak responses obtained from theAssay preparation and theStandard preparation,respectively.