A: Infrared Absorption á197Kñ.

B: It responds to the test for Chloride á191ñwhen tested as directed for alkaloidal hydrochlorides.

Buffer— Prepare a solution of 0.025Mmonobasic potassium phosphate containing 0.1%(w/v)of tetrabutylammonium bromide.Adjust with 0.025Mphosphoric acid to a pHof 3.0.

Mobile phase— Prepare a suitable filtered and degassed mixture of Bufferand acetonitrile (85:15).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Resolution solution— Prepare a solution in Mobile phasecontaining 2.0mg of USP Betaxolol Hydrochloride RSand 1mg of alprenolol hydrochloride per mL.

Test preparation— Prepare a solution of Betaxolol Hydrochloride in Mobile phasecontaining 2.0mg per mL.

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 5-µm packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Resolution solution,and record the peak responses as directed for Procedure:the relative retention times are about 0.9for alprenolol and 1.0for betaxolol;the resolution,R,between the two peaks is not less than 1.0;the tailing factors for the two peaks are not more than 2.0;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Inject about 20µLof the Test preparationinto the chromatograph,record the chromatogram,and measure the areas for the peaks.[NOTE—Allow the elution to continue for about five times the elution time of the betaxolol peak before making the next injection.]Calculate the percentage of each impurity by the same formula: in which riis the response of each individual peak,other than the main betaxolol peak,in the chromatogram obtained from the Test preparation,and rSis the sum of the responses of all the peaks obtained in the chromatogram from the Test preparation:the sum of all impurities found is not more than 1.0%.