A: Place 10mLof water in a small beaker,and deliver 10sprays from the Aerosol under the surface of the water,actuating the valve by pressing the tip against the bottom of the beaker.Filter,and to 5mLof the filtrate add 1drop of dilute hydrochloric acid (1in 120).Add 0.50mLof 0.10Niodine,allow to stand for 5minutes,and add 1.0mLof 0.10Nsodium thiosulfate:a red-brown color is produced.

B: Aportion of the filtrate obtained in Identificationtest Aresponds to the tests for Sulfate á191ñ.

PROCEDUREFOR DOSE UNIFORMITY—

Ferro-citrate solution and Buffer solution—Prepare as directed under Epinephrine Assay á391ñ.

Standard preparation— Transfer about 50mg of USP Isoproterenol Hydrochloride RS,accurately weighed,to a 100-mLvolumetric flask,add a freshly prepared solution of sodium bisulfite (1in 500)to volume,and mix.Transfer 10.0mLof this solution to a second 100-mLvolumetric flask,dilute with the sodium bisulfite solution to volume,and mix.The concentration of USP Isoproterenol Hydrochloride RSin the Standard preparationis about 50µg per mL.

Assay preparation— [NOTE—Asuitable sampling beaker is one having a small indentation formed in its inside bottom surface having dimensions adequate to accept the aerosol valve stem during actuation,thereby preventing particle entrapment and side-of-stem leakage during the sample delivery.]Place 20mLof chloroform in a suitable 100-mLbeaker.Prime the valve of the Aerosol by alternately shaking and firing it 10times through its oral inhalation actuator.Accurately weigh the Aerosol,shake it,and immediately deliver a single spray under the surface of the chloroform,actuating the valve by pressing the tip into the indentation in the bottom of the beaker.Raise the Aerosol above the surface of the chloroform,and shake it gently preparatory to delivering another spray similarly under the surface of the chloroform.Deliver a total of 5sprays in this manner.Rinse the valve stem and ferrule with about 2mLof chloroform,collecting the rinsing with the sample in the beaker.Allow the Aerosol to dry,weigh it,and determine the total weight of the 5sprays.Transfer the solution to a centrifuge tube with the aid of two 3-mLportions of chloroform,and add 10.0mLof freshly prepared sodium bisulfite solution (1in 500).Insert the stopper,shake vigorously for 1minute,centrifuge for 5minutes,and use the clear supernatant as directed in the Procedure.

Procedure— Transfer 5.0mLeach of the Standard preparationand the Assay preparationto separate test tubes.To each tube add 100µLof Ferro-citrate solutionand 1.0mLof Buffer solution,and mix.Concomitantly determine the absorbances of the solutions in 1-cm cells at the wavelength of maximum absorbance at about 530nm,with a suitable spectrophotometer,using water as the blank.Calculate the quantity,in mg,of (C11H17NO3)2·H2SO4in each mLof the Aerosol taken by the formula: in which 260.30is one-half of the molecular weight of isoproterenol sulfate (anhydrous),and 247.72is the molecular weight of isoproterenol hydrochloride,Cis the concentration,in µg per mL,of USP Isoproterenol Hydrochloride RSin the Standard preparation,dis the density,in g per mL,of the Aerosol,Wis the weight,in g,of the portion of Inhalation Aerosol taken,and AUand ASare the absorbances of the solutions from the Assay preparationand the Standard preparation,respectively.[The density,d,is determined as follows.Weigh a known volume (v)of the Inhalation Aerosol in a suitable,gas-tight,5-mLsyringe equipped with a linear valve.Calibrate the volume of the syringe by filling to the 5-mLmark with dichlorotetrafluoroethane withdrawn from a plastic-coated glass vial sealed with a neoprene multiple-dose rubber stopper and an aluminum seal,using 1.456g per mLas the density of the calibrating liquid.Maintain the dichlorotetrafluoroethane,the Aerosol assay specimen,and the syringe (protected from becoming wet)in a water bath at 25.Obtain the specimen equivalent to the same volume as that obtained during the sampling procedure,from the Aerosol by means of a sampling device consisting of a replaceable rubber septum engaged in the plate threads at one end of a threaded fitting,the opposite end of which contains a sharpened tube capable of puncturing the aerosol container,and a rubber gasket around the tube to prevent leakage of the container contents after puncture.*Record the weight of the volume (v)of the Aerosol as w,and calculate the density by the formula w/v.]