A:Infrared Absorption á197Kñ.

B:Ultraviolet Absorption á197Uñ—

C: It responds to the tests for Chloride á191ñ.

Standard solutionand Standard dilutions— Prepare a solution of USP Dopamine Hydrochloride RSin methanol to contain 30mg per mL(Standard solution).Prepare a series of dilutions of the Standard solutionin methanol to contain 0.6mg,0.3mg,and 0.15mg per mL(Standard dilutions),corresponding to 2.0%,1.0%,and 0.5%of impurities,respectively.

Test solution— Transfer 150mg of Dopamine Hydrochloride to a 5-mLvolumetric flask,dilute with methanol to volume,and mix.

Procedure— In a suitable chromatographic chamber arranged for thin-layer chromatography (see Chromatography á621ñ),place a solvent system consisting of 13volumes of chloroform,9volumes of methanol,and 4volumes of dilute glacial acetic acid (3in 10).Line the chamber with filter paper,and allow to equilibrate.Apply 10-µLportions of the Standard solution,the Standard dilutions,and the Test solutionto a 20-×20-cm chromatographic plate coated with a 0.25-mm layer of chromatographic silica gel mixture.Develop the chromatogram until the solvent front has moved about 15cm.Remove the plate from the developing chamber,allow to dry at room temperature for several minutes,and spray evenly with a freshly prepared mixture containing equal volumes of ferric chloride solution (1in 10)and potassium ferricyanide solution (1in 20).[Dopamine and its related impurities appear as blue spots under visible light.]The Test solutionexhibits its principal spot at an RFvalue corresponding to that of the Standard solutionand not more than three secondary spots.Estimate the concentration of any secondary spots exhibited by the Test solutionby comparison with the Standard dilutions:the sum of the impurities is not greater than 1.0%.