A:Infrared Absorption á197Kñ.

B:Ultraviolet Absorption á197Uñ—

Mobile phaseand Chromatographic system— Prepare as directed in the Assay.

Test solution— Transfer about 10mg of Atenolol to a 100-mLvolumetric flask,dissolve in and dilute with Mobile phaseto volume,and mix.

Diluted test solution— Transfer 0.50mLof the Test solutionto a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Procedure— Separately inject equal volumes (about 50µL)of the Test solutionand the Diluted test solutioninto the chromatograph,record the chromatograms,and measure the areas for all the peaks.[NOTE—Chromatograph the Test solution for a period of time 6times the retention time of the atenolol peak.]Calculate the percentage of each impurity observed in the chromatogram obtained from the Test solutionby the formula: in which riis the peak response of an individual impurity in the chromatogram obtained from the Test solution;and rAis the response of the main atenolol peak in the chromatogram obtained from the Diluted test solution.Not more than 0.25%of any individual impurity is found,and the sum of all the impurities is not more than 0.5%.

Mobile phase— Dissolve 1.1g of sodium 1-heptanesulfonate and 0.71g of anhydrous dibasic sodium phosphate in 700mLof water.Add 2mLof dibutylamine,and adjust with 0.8Mphosphoric acid to a pHof 3.0.Add 300mLof methanol,mix,and pass through a filter having a 0.5µm or finer porosity.Degas this solution before use.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Quantitatively dissolve an accurately weighed quantity of USP Atenolol RSin Mobile phaseto obtain a solution having a known concentration of about 0.01mg per mL.

Assay preparation— Transfer about 100mg of Atenolol,accurately weighed,to a 100-mLvolumetric flask,add 50mLof Mobile phase,and sonicate for about 5minutes.Dilute with Mobile phaseto volume,and mix.Transfer 5.0mLof this solution to a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.Transfer 5.0mLof this solution to a second 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 226-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 0.6mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency is not less than 5000theoretical plates;the tailing factor is not more than 2.0;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 preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C14H22N2O3in the portion of Atenolol taken by the formula: in which Cis the concentration,in mg per mL,of USP Atenolol RSin the Standard preparation;and rUand rSare the atenolol peak responses obtained from the Assay preparationand the Standard preparation,respectively.