á391ñEPINEPHRINE ASSAY

USP Reference Standards á11ñ— USP Epinephrine Bitartrate RS.

Ferro-citrate Solution— On the day needed,dissolve 1.5g of ferrous sulfate in 200mLof water to which have been added 1.0mLof dilute hydrochloric acid (1in 12)and 1.0g of sodium bisulfite.Dissolve 500mg of sodium citrate in 10mLof this solution,and mix.

Buffer Solution— In a 50-mLvolumetric flask mix 4.2g of sodium bicarbonate,5.0g of potassium bicarbonate,and 18mLof water (not all of the solids will dissolve at this stage).To another 18mLof water add 3.75g of aminoacetic acid and 1.7mLof 6Nammonium hydroxide,mix to dissolve,and transfer this solution to the 50-mLvolumetric flask containing the other mixture.Dilute with water to volume,and mix until solution is complete.

Standard Preparation— Transfer about 18mg of USP Epinephrine Bitartrate RS,accurately weighed,to a 100-mLvolumetric flask with the aid of 20mLof sodium bisulfite solution (1in 50),dilute with water to volume,and mix.Transfer 5.0mLof this solution to a 50-mLvolumetric flask,dilute with sodium bisulfite solution (1in 500)to volume,and mix.[NOTE—Make the final dilution when the assay is carried out.]The concentration of USP Epinephrine Bitartrate RSin the Standard Preparationis about 18µg per mL.

Assay Preparation— Transfer to a 50-mLvolumetric flask an accurately measured volume of the Injection under assay,equivalent to about 500µg of epinephrine,dilute with sodium bisulfite solution (1in 500)to volume,if necessary,and mix.[NOTE—The final concentration of sodium bisulfite is in the range of 1to 3mg per mL,any bisulfite present in the Injection under assay being taken into consideration.]

Procedure— Into three 50-mLglass-stoppered conical flasks transfer,separately,20.0-mLaliquots of the Standard Preparation,the Assay Preparation,and sodium bisulfite solution (1in 500)to provide the blank.To each flask add 200µLof Ferro-citrate Solutionand 2.0mLof Buffer Solution,mix,and allow the solutions to stand for 30minutes.Determine the absorbances of the solutions in 5-cm cells at the wavelength of maximum absorbance at about 530nm,with a suitable spectrophotometer,using the blank to set the instrument.Calculate the quantity,in mg,of epinephrine (C9H13NO3)in each mLof the Injection taken by the formula: in which 183.21and 333.30are the molecular weights of epinephrine and epinephrine bitartrate,respectively;Cis the concentration,in µg per mL,of USP Epinephrine Bitartrate RSin the Standard Preparation;and Vis the volume,in mL,of Injection taken.