A: Infrared Absorption á197Kñ.

B: Asolution (1in 100)responds to the tests for Chloride á191ñ.

Standard preparation— Dissolve an accurately weighed quantity of USP Isoetharine Hydrochloride RSin freshly prepared sodium bisulfite solution (3in 1000)to obtain a solution having a concentration of about 5mg per mL.Transfer 5.0mLof this solution to a 50-mLvolumetric flask,dilute with 0.17Nacetic acid to volume,and mix to obtain a solution having a known concentration of about 500µg per mL.

Assay preparation— Transfer about 125mg of Isoetharine Hydrochloride,accurately weighed,to a 25-mLvolumetric flask,dissolve in sodium bisulfite solution (3in 1000),dilute with sodium bisulfite solution to volume,and mix.Transfer 5.0mLof this solution to a 50-mLvolumetric flask,dilute with 0.17Nacetic acid to volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 278-nm detector and a 4-mm ×30-cm column that contains packing L1.The mobile phase is 0.17Nacetic acid,having a flow rate of about 2.2mLper minute.Chromatograph five replicate injections of the Standard preparation,and record the peak responses as directed under Procedure:the relative standard deviation is not more than 3.0%.

Procedure— Using a microsyringe or sampling valve,chromatograph 10µLof the Standard preparation,and adjust the specimen size and other operating parameters,if necessary,until satisfactory chromatography and peak responses are obtained.Chromatograph equal volumes of the Standard preparationand the Assay preparation,record the chromatograms,and measure the peak responses.Calculate the quantity,in mg,of C13H21NO3·HCl in the portion of Isoetharine Hydrochloride taken by the formula: in which Cis the concentration,in µg per mL,of USP Isoetharine Hydrochloride RSin the Standard preparation,and hUand hSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.