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

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

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

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

Procedure— Apply 5-µL portions of Epinephrine standard solution, Norepinephrine standard solution, and Test solution to a suitable thin-layer chromatographic plate (see Chromatography 621) 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 (1 in 10): the RF value of the principal spot obtained from the Test solution corresponds to that obtained from the Epinephrine standard solution. Any spot obtained from the Test solution is not larger nor more intense than the spot with the same RF value obtained from the Norepinephrine standard solution, corresponding to not more than 4.0% of norepinephrine.

Ferro-citrate solution, Buffer solution, and Standard preparation— Prepare as directed under Epinephrine Assay 391.

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

Procedure— Proceed as directed for Procedure under Epinephrine Assay 391. Calculate the quantity, in mg, of C9H13NO3 in the portion of Racepinephrine taken by the formula: in which 183.20 and 333.29 are the molecular weights of racepinephrine and epinephrine bitartrate, respectively, C is the concentration, in µg per mL, of USP Epinephrine Bitartrate RS in the Standard preparation, and AU and AS are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.