A: Infrared Absorption á197Kñ.

B: It responds to the test for dry chlorides in Chloride á191ñ.

Solution A— Dissolve 2.60g of sodium 1-octanesulfonate in 1000mLof water,pipet 3mLof triethylamine into the solution,and mix.Adjust the solution with phosphoric acid to a pHof 2.5.Filter and degas before use.

Solution B— Prepare a filtered and degassed mixture of methanol and acetonitrile (82:18).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Diluting solution— Prepare a mixture of Solution Aand Solution B(1:1).

Mobile phase— Use variable mixtures of Solution Aand Solution Bas directed for Chromatographic system.Make adjustments to either Solution if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard solution— Dissolve an accurately weighed quantity of USP Dobutamine Hydrochloride RSin Diluting solution and dilute quantitatively,and stepwise if necessary,with Diluting solution to obtain a solution having a known concentration of about 0.05mg per mL.

Test solution— Transfer about 50.0mg of Dobutamine Hydrochloride,accurately weighed,to a 10-mLvolumetric flask,dissolve in and dilute with Diluting solutionto volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 280-nm detector and a 4.6-mm ×15-cm column that contains packing L1.The flow rate is about 1mLper minute.The chromatograph is programmed as follows. Chromatograph the Standard solution,and record the peak responses as directed for Procedure:the tailing factor is not more than 2.0;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure all of the peak responses.Calculate the percentage of each impurity in the portion of Dobutamine Hydrochloride taken by the formula: in which Cis the concentration,in mg per mL,of USP Dobutamine Hydrochloride RSin the Standard solution;Dis the concentration,in mg per mL,of Dobutamine Hydrochloride in the Test solution;riis the peak response for each impurity found in the Test solution;and rSis the dobutamine response obtained from the Standard solution:not more than 0.5%of any individual impurity is found,and not more than 1.0%of total impurities is found.

Phosphate buffer— Transfer about 23g of monobasic ammonium phosphate to a 2-liter volumetric flask,add 1900mLof water,and mix.Adjust with phosphoric acid to a pHof 2.2,dilute with water to volume,and mix.

Mobile phase— Prepare a filtered and degassed mixture of Phosphate bufferand acetonitrile (4:1).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Dobutamine Hydrochloride RSin water,and dilute quantitatively,and stepwise if necessary,with water to obtain a solution having a known concentration of about 0.5mg per mL.[NOTE—Prepare fresh daily,and refrigerate until injected.]

System suitability solution— Dissolve suitable quantities of 5-(hydroxymethyl)furfural and USP Dobutamine Hydrochloride RSin water to obtain a solution containing about 0.01and 0.5mg per mL,respectively.

Assay preparation— Transfer about 50mg of Dobutamine Hydrochloride,accurately weighed,to a 100-mLvolumetric flask,dissolve in and dilute with water to volume,and mix.[NOTE—Refrigerate until injected,and use within 8hours.]

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 280-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the System suitability solution,and record the peak responses as directed under Procedure:the relative retention times are 1.0for dobutamine and not more than 0.62for 5-(hydroxymethyl)furfural,and the retention time of dobutamine is not more than 5.3minutes.Chromatograph the Standard preparation,and record the peak responses as directed under Procedure:the tailing factor is not more than 2.0,and the relative standard deviation for replicate injections is 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 C18H23NO3·HCl in the portion of Dobutamine Hydrochloride taken by the formula: in which Cis the concentration,in mg per mL,of USP Dobutamine Hydrochloride RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.