Medium: water;900mL.

Apparatus 2: 50rpm.

Time: 45minutes.

Procedure— Determine the amount of C11H17NO3·HCl dissolved from UVabsorbances at the wavelength of maximum absorbance at about 279nm 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 RSin the same medium.

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

Procedure for content uniformity— Crush 1Tablet,and transfer it with the aid of 25mLof water to a 50-mLvolumetric 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 20mLof the filtrate.Transfer a portion of the filtrate,equivalent to about 2.5mg of isoproterenol hydrochloride and accurately measured,to a 50-mLvolumetric flask,dilute with water to volume,and mix.Dissolve an accurately weighed quantity of USP Isoproterenol Hydrochloride RSin water,and dilute quantitatively and stepwise with water to obtain a Standard solution having a known concentration of about 50µg per mL.Concomitantly and without delay,determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 279nm,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 Cis the concentration,in µg per mL,of USP Isoproterenol Hydrochloride RSin the Standard solution,Vis the volume,in mL,of the filtrate taken,and AUand ASare the absorbances of the solution from the Tablet and the Standard solution,respectively.

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

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

Assay preparation— Weigh and finely powder not less than 20Tablets.Weigh accurately a portion of the powder,equivalent to about 10mg of isoproterenol hydrochloride,and transfer with the aid of 50mLof 0.1Nsulfuric acid to a 100-mLvolumetric 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 20mLof the filtrate.

Chromatographic system (see Chromatography á621ñ)—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 1mLper 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 20µL)of the Standard preparationand the Assay preparationinto 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 3.5minutes for isoproterenol.Calculate the quantity,in mg,of C11H17NO3·HCl in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Isoproterenol Hydrochloride RSin the Standard preparation,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.