A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

Mobile phase and Chromatographic system— Prepare as directed in the Assay.

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

Diluted test solution— Transfer 0.50 mL of the Test solution to a 100-mL volumetric flask, dilute with Mobile phase to volume, and mix.

Procedure— Separately inject equal volumes (about 50 µL) of the Test solution and the Diluted test solution into the chromatograph, record the chromatograms, and measure the areas for all the peaks. [note—Chromatograph the Test solution for a period of time 6 times the retention time of the atenolol peak.] Calculate the percentage of each impurity observed in the chromatogram obtained from the Test solution by the formula: in which ri is the peak response of an individual impurity in the chromatogram obtained from the Test solution; and rA is 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 1.1 g of sodium 1-heptanesulfonate and 0.71 g of anhydrous dibasic sodium phosphate in 700 mL of water. Add 2 mL of dibutylamine, and adjust with 0.8 M phosphoric acid to a pH of 3.0. Add 300 mL of methanol, mix, and pass through a filter having a 0.5-µm or finer porosity. Degas this solution before use. Make adjustments if necessary (see System Suitability under Chromatography 621).

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

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

Chromatographic system (see Chromatography 621)— 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 0.6 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency is not less than 5000 theoretical 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 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C14H22N2O3 in the portion of Atenolol taken by the formula: in which C is the concentration, in mg per mL, of USP Atenolol RS in the Standard preparation; and rU and rS are the atenolol peak responses obtained from the Assay preparation and the Standard preparation, respectively.