A: It responds to the Identification tests under Bupivacaine Hydrochloride Injection.

B: Pipet a volume of Injection, equivalent to about 50 µg of epinephrine, into a suitable container, add 0.1 mL of Ferro-citrate solution and 2.0 mL of Buffer solution (prepared as directed under Epinephrine Assay 391), mix, and allow the solution to stand for 10 minutes. Filter the solution: the filtrate is violet in color and may turn brownish.

pH 6.8 Phosphate buffer , Mobile phase, Internal standard solution, Standard preparation, Chromatographic system, and Procedure—Proceed as directed in the Assay under Bupivacaine Hydrochloride Injection.

Assay preparation— Transfer an accurately measured volume of Injection, equivalent to about 50 mg of bupivacaine hydrochloride, to a 100-mL volumetric flask, add 10.0 mL of Internal standard solution, dilute with methanol to volume, and mix.

Mobile phase— Prepare a suitably filtered and degassed mixture of water, methanol, and 2M monobasic sodium phosphate (900:50:50), containing in each 1000 mL, 40 mg of edetate disodium, 0.4 mL of phosphoric acid, and 0.4 g of sodium 1-octanesulfonate. Make adjustments, if necessary, to obtain a retention time of not less than 11 minutes for the epinephrine peak (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Epinephrine Bitartrate RS in Mobile phase to obtain a solution having a concentration of about 2 µg per mL.

Resolution solution— Dissolve suitable quantities of epinephrine bitartrate and dopamine hydrochloride in Mobile phase to obtain a solution containing about 2 µg of each per mL.

Assay preparation— Transfer an accurately measured volume of Injection, equivalent to about 25 µg of epinephrine, to a 25-mL volumetric flask, dilute with Mobile phase to volume, and mix.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with an electrochemical detector held at a potential of +0.75 volt and a 4.6-mm × 25-cm column that contains packing L1. The flow rate is about 1.2 mL per minute. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the resolution, R, between the epinephrine and dopamine peaks is not less than 6.0; and the relative retention times are about 2 for dopamine and 1.0 for epinephrine. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in µg, of epinephrine (C9H13NO3) in each mL of the Injection taken by the formula: in which 183.21 and 333.30 are the molecular weights of epinephrine and epinephrine bitartrate, respectively; C is the concentration, in µg per mL, of USP Epinephrine Bitartrate RS in the Standard preparation; V is the volume, in mL, of Injection taken; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.