Medium: water; 900 mL.

Apparatus 2: 50 rpm.

Time: 45 minutes.

Procedure— Determine the amount of C11H17NO3·HCl dissolved from UV absorbances at the wavelength of maximum absorbance at about 279 nm of filtered portions of the solution under test, suitably diluted with Dissolution Medium, if necessary, in comparison with a Standard solution having a known concentration of USP Isoproterenol Hydrochloride RS in the same medium.

Tolerances— Not less than 75% (Q) of the labeled amount of C11H17NO3·HCl is dissolved in 45 minutes.

Procedure for content uniformity— Crush 1 Tablet, and transfer it with the aid of 25 mL of water to a 50-mL volumetric flask. Shake gently until no more dissolves, add water to volume, and mix. Filter through a dry filter into a dry flask, rejecting the first 20 mL of the filtrate. Transfer a portion of the filtrate, equivalent to about 2.5 mg of isoproterenol hydrochloride and accurately measured, to a 50-mL volumetric flask, dilute with water to volume, and mix. Dissolve an accurately weighed quantity of USP Isoproterenol Hydrochloride RS in water, and dilute quantitatively and stepwise with water to obtain a Standard solution having a known concentration of about 50 µg per mL. Concomitantly and without delay, determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 279 nm, with a suitable spectrophotometer, using water as the blank. Calculate the quantity, in mg, of C11H17NO3·HCl in the Tablet taken by the formula: in which C is the concentration, in µg per mL, of USP Isoproterenol Hydrochloride RS in the Standard solution; V is the volume, in mL, of the filtrate taken; and AU and AS are the absorbances of the solution from the Tablet and the Standard solution, respectively.

Mobile phase— Adjust 0.1 M sodium sulfate with phosphoric acid to a pH of 3.0. Mix 90 parts of this solution with 10 parts of methanol.

Standard preparation— Dissolve an accurately weighed quantity of USP Isoproterenol Hydrochloride RS in 0.1 N sulfuric acid, and dilute quantitatively and stepwise with the same solvent to obtain a solution having a known concentration of about 0.1 mg per mL.

Assay preparation— Weigh and finely powder not less than 20 Tablets. Weigh accurately a portion of the powder, equivalent to about 10 mg of isoproterenol hydrochloride, and transfer with the aid of 50 mL of 0.1 N sulfuric acid to a 100-mL volumetric flask. Shake gently until no more dissolves, dilute with the same solvent to volume, and mix. Filter through a dry filter into a dry flask, rejecting the first 20 mL of the filtrate.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 280-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The flow rate is about 1 mL per minute. Chromatograph three replicate injections of the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation 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 by means of a suitable microsyringe or sampling valve, record the chromatograms, and measure the responses for the major peaks. The retention time is about 3.5 minutes for isoproterenol. Calculate the quantity, in mg, of C11H17NO3·HCl in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Isoproterenol Hydrochloride RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.