Standard solution— Transfer 2.0 mL of 0.100 N iodine VS to a 500-mL volumetric flask, dilute with water to volume, and mix.

Procedure— Visually examine a portion of the Inhalation Solution (Test solution) in a suitable clear glass test tube against a white background: it is not pinkish and it contains no precipitate. If any yellow color is observed in the Test solution, concomitantly determine the absorbances of the Test solution and the Standard solution in 1-cm cells with a suitable spectrophotometer set at 460 nm: the absorbance of the Test solution does not exceed that of the Standard solution.

(Official January 1, 2007)

Mobile phase— Prepare a filtered and degassed mixture of 0.05 M monobasic sodium phosphate and methanol (85:15). Dissolve a suitable quantity of sodium 1-octanesulfonate in this mixture to obtain a solution that is 0.005 M with respect to sodium 1-octanesulfonate. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Epinephrine Bitartrate RS in a mixture of 0.05 M monobasic sodium phosphate and methanol (85:15), and dilute quantitatively, and stepwise if necessary, with the same solvent mixture to obtain a solution having a known concentration of about 0.1 mg per mL.

Assay preparation— Transfer an accurately measured volume of Inhalation Solution, equivalent to about 11 mg of racepinephrine, to a 200-mL volumetric flask, dilute with a mixture of 0.05 M monobasic sodium phosphate and methanol (85:15) to volume, and mix.

System suitability preparation— Dissolve a suitable quantity of dopamine hydrochloride in a mixture of 0.05 M monobasic sodium phosphate and methanol (85:15) to obtain a solution containing about 0.1 mg per mL. Transfer 20.0 mL of this solution to a 50-mL volumetric flask. Add 5.0 mL of the Standard preparation, dilute with a mixture of 0.05 M monobasic sodium phosphate and methanol (85:15) to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 280-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The flow rate is about 1 mL per minute. Chromatograph the Standard preparation and the System suitability preparation, and record the peak responses as directed for Procedure: the tailing factor for the analyte peak is not more than 1.2, the resolution, R, between the dopamine and analyte peak is not less than 5.0, 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 C9H13NO3 in each mL of the Inhalation Solution 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 mg per mL, of USP Epinephrine Bitartrate RS in the Standard preparation; V is the volume, in mL, of Inhalation Solution taken; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.