A: Evaporate a 1-mL portion to dryness: the residue so obtained meets the requirements for Identification test A under Metaraminol Bitartrate.

B: It meets the requirements for Identification tests B and C under Metaraminol Bitartrate.

(Official January 1, 2007)

0.0032 M Hexanesulfonate buffer— Mix 600 mg of sodium 1-hexanesulfonate with water to obtain 1000 mL of solution, adjust with phosphoric acid to a pH of 3.0 ± 0.05, and filter.

Mobile phase— Prepare a suitable degassed and filtered mixture of methanol and 0.0032 M Hexanesulfonate buffer (7:3). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Metaraminol Bitartrate RS in water to obtain a solution having a known concentration of about 0.2 mg of metaraminol per mL.

Assay preparation— Transfer an accurately measured volume of Injection, equivalent to about 20 mg of metaraminol, to a 100-mL volumetric flask, dilute with water to volume, and mix.

System suitability preparation— Prepare a solution of propylparaben in alcohol containing 0.4 mg per mL. Mix 1 volume of this solution with 99 volumes of the Standard preparation.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 264-nm detector and a 4-mm × 25-cm column that contains packing L7. The flow rate is about 1 mL per minute. Chromatograph the System suitability preparation and the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency is not less than 2600 theoretical plates, the resolution, R, between the metaraminol bitartrate and propylparaben peaks is not less than 3.0 with propylparaben eluting first, and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10 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 mg, of metaraminol (C9H13NO2) in each mL of the Injection taken by the formula: in which C is the concentration, in mg per mL, of metaraminol represented by the USP Metaraminol 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.