A: The UVabsorption spectrum of the Assay preparationprepared as directed in the Assayexhibits maxima and minima at the same wavelengths as that of a similar solution of USP Epinephrine Bitartrate RS.

B: Asolution (1in 2)is levorotatory.

pH5.8Buffer— Mix 1volume of 1Mdibasic potassium phosphate with 9volumes of 1Mmonobasic potassium phosphate.Adjust by the addition of small volumes of either solution to a pHof 5.80±0.05.

Standard preparation— Dissolve a suitable quantity of USP Epinephrine Bitartrate RS,accurately weighed,in 0.1Nhydrochloric acid to obtain a solution having a known concentration of about 40µg of epinephrine per mL.

Assay preparation— Transfer an accurately measured volume of Ophthalmic Solution,equivalent to about 20mg of epinephrine,to a 250-mLbeaker containing 2.0mLof pH5.8Buffer.Add 9g of chromatographic siliceous earth,and mix.Carefully transfer the mixture to a 45-×2.2-cm chromatographic tube containing a pledget of glass wool at the bottom,and tap the column gently to effect packing.Dry-wash the beaker with about 1g of chromatographic siliceous earth,add to the column,and plug the top with a pledget of glass wool.Wash the column with 100mLof water-washed ether,and discard the eluant.Add 10.0mLof 0.1Nhydrochloric acid to a 125-mLseparator,and place the separator under the column.To about 100mLof water-washed ether add 1mLof bis(2-ethylhexyl)phosphoric acid,and elute the column with this solution,collecting the eluate in the separator.Extract the epinephrine into the aqueous acid layer,and carefully transfer the aqueous layer to a 500-mLvolumetric flask.Shake the ether layer with two 50-mLportions of 0.1Nhydrochloric acid,add the acidic aqueous extracts to the volumetric flask,dilute with 0.1Nhydrochloric acid to volume,and mix.

Procedure— Concomitantly determine the absorbances of the Assay preparationand the Standard preparationat the wavelength of maximum absorbance at about 280nm,with a suitable spectrophotometer,using 0.1Nhydrochloric acid as the blank.Calculate the quantity,in mg,of C9H13NO3in each mLof the Ophthalmic Solution taken by the formula: in which Cis the concentration,in µg per mL,of epinephrine in the Standard preparation;Vis the volume,in mL,of Ophthalmic Solution taken;and AUand ASare the absorbances of the Assay preparationand the Standard preparation,respectively.