Test solution: 10mg per mL,in 0.6Nhydrochloric acid.

Epinephrine standard solution— Dilute with methanol an accurately measured volume of a solution of USP Epinephrine Bitartrate RSin formic acid containing about 364mg per mLto obtain a solution having a concentration of about 20mg per mL.

Norepinephrine standard solution— Dilute with methanol an accurately measured volume of a solution of USP Norepinephrine Bitartrate RSin formic acid containing 16mg per mLto obtain a solution having a known concentration of 1.6mg per mL.

Test solution— Dissolve 200mg of Racepinephrine in 1.0mLof formic acid,dilute with methanol to 10.0mL,and mix.

Procedure— Apply 5-µLportions of Epinephrine standard solution,Norepinephrine standard solution,and Test solutionto a suitable thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Allow to dry,and develop the chromatogram in an unsaturated tank using a solvent system consisting of a mixture of n-butanol,water,and formic acid (7:2:1)until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,mark the solvent front,and allow the solvent to evaporate in warm circulating air.Spray with Folin-Ciocalteu Phenol TS,followed by sodium carbonate solution (1in 10):the RFvalue of the principal spot obtained from the Test solutioncorresponds to that obtained from the Epinephrine standard solution.Any spot obtained from the Test solutionis not larger nor more intense than the spot with the same RFvalue obtained from the Norepinephrine standard solution,corresponding to not more than 4.0%of norepinephrine.

Solvent— Use dimethyl sulfoxide.

Ferro-citrate solution,Buffer solution,andStandard preparation— Prepare as directed under Epinephrine Assay á391ñ.

Assay preparation— Transfer about 10mg of Racepinephrine,accurately weighed,to a 1-liter volumetric flask.Dilute with sodium bisulfite solution (1in 500)to volume,and mix.

Procedure— Proceed as directed for Procedureunder Epinephrine Assay á391ñ.Calculate the quantity,in mg,of C9H13NO3in the portion of Racepinephrine taken by the formula: in which 183.20and 333.29are the molecular weights of racepinephrine and epinephrine bitartrate,respectively,Cis the concentration,in µg per mL,of USP Epinephrine Bitartrate RSin the Standard preparation,and AUand ASare the absorbances of the solutions from the Assay preparationand the Standard preparation,respectively.