Medium: 0.01Nhydrochloric acid;500mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Procedure— Determine the amount of C18H29NO3·HCl dissolved by employing UVabsorption at the wavelength of maximum absorbance at about 274nm on filtered portions of the solution under test in comparison with a Standard solution having a known concentration of USP Betaxolol Hydrochloride RSin the same Medium.A5-cm pathlength cell may be used for lower dosage levels.

Tolerances— Not less than 80%(Q)of the labeled amount of C18H29NO3·HCl is dissolved in 30minutes.

Procedure for content uniformity— Place 1Tablet in a volumetric flask of appropriate size to obtain a concentration,based on the labeled amount of betaxolol hydrochloride per Tablet,of about 0.1mg per mLwhen diluted.Add an amount of 0.1Nhydrochloric acid equal to about 70%of the volume of the flask,shake by mechanical means until dissolved,dilute with 0.1Nhydrochloric acid to volume,and mix.Filter the mixture,discarding the first 20mLof the filtrate.Concomitantly determine the absorbances of the clear filtrate and of a Standard solution of USP Betaxolol Hydrochloride RSin 0.1Nhydrochloric acid having a known concentration of about 0.1mg per mL,in 1-cm cells,at the wavelength of maximum absorbance at about 274nm,using 0.1Nhydrochloric acid as the blank.Calculate the quantity,in mg,of betaxolol hydrochloride (C18H29NO3·HCl)in the Tablet taken by the formula: in which C,is the concentration,in mg per mL,of USP Betaxolol Hydrochloride RSin the Standard solution;Vis the volume,in mL,of 0.1Nhydrochloric acid used to dissolve the Tablet;and AUand ASare the absorbances of the solution from the Tablet and the Standard solution,respectively.

Mobile phase— Prepare a filtered mixture of 0.025MpH6.0ammonium phosphate buffer,acetonitrile,and methanol (35:35:30).Mix,and degas under vacuum while stirring.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Diluent— Prepare a mixture of acetonitrile and water (1:1).

Standard preparation— Dissolve an accurately weighed quantity of USP Betaxolol Hydrochloride RSin Diluentto obtain a solution having a known concentration of about 2mg per mL.

Assay preparation— Dissolve not fewer than 20Tablets in an appropriate accurately measured volume of Diluentso that the final concentration,based on the labeled amount per Tablet,is about 2mg of betaxolol hydrochloride per mL.Sonicate until the Tablets are disintegrated.Cool to room temperature,dilute with Diluentto volume,mix,and filter.Use the clear filtrate as the Assay preparation.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 273-nm detector and a 4.6-mm ×15-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,record the chromatogram,and measure the peak response as directed for Procedure:the tailing factor is not more than 3.0,and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparation,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of betaxolol hydrochloride (C18H29NO3·HCl)in each Tablet taken by the formula: in which Cis the concentration,in mg per mL,of USP Betaxolol Hydrochloride RSin the Standard preparation;Vis the volume of Diluentused to dissolve the Tablets;Nis the number of Tablets taken;and rUand rSare the betaxolol peak responses obtained from the Assay preparationand the Standard preparation,respectively.