Relative molecular mass. 266.3
Chemical name. 2-[p-[2-Hydroxy-3-(isopropylamino)propoxy]phenyl]acetamide (racemate); CAS Reg. No. 29122-68-7.
Description. A white or almost white powder.
Solubility. Sparingly soluble in water; soluble in ethanol (~750 g/l) TS; slightly soluble in dichloromethane R.
Category. Cardiovascular agent; β-adrenoreceptor blocking agent.
Storage. Atenolol should be kept in a tightly closed container.
Atenolol contains not less than 99.0% and not more than 101.0% of C14H22N2O3, calculated with reference to the dried substance.
• Either tests A and D or tests B, C, and D may be applied.
A. Carry out the examination as described under 1.7 Spectrophotometry in the infrared region. The infrared absorption spectrum is concordant with the spectrum obtained from atenolol RS or with the reference spectrum of atenolol.
B. The absorption spectrum of a 0.10 mg/ml solution in methanol R, when observed between 230nm and 350nm, exhibits 2 maxima at about 275nm and 282nm. The ratio of the absorbance at 275 nm to that at 282nm is between 1.15 and 1.20.
C. Carry out the test as described under 1.14.1 Thin-layer chromatography, using silica gel R4 as the coating substance and a mixture of 99 volumes of methanol R and 1 volume of ammonia (~260g/l) TS as the mobile phase. Apply separately to the plate 10 μl of each of 2 solutions in methanol R containing (A) 10 mg of Atenolol per ml, and (B) 10mg of atenolol RS per ml. After removing the plate from the chromatographic chamber, allow it to dry in air, and examine the chromatogram in ultraviolet light (254 nm).
The principal spot obtained with solution A corresponds in position, appearance, and intensity with that obtained with solution B.
D. Melting temperature, about 154 °C.
Chlorides. Dissolve 0.25 g in a mixture of 2 ml of nitric acid (~130 g/l) TS and 20 ml of water, and proceed as described under 2.2.1 Limit test for chlorides; the chloride content is not more than 1.0 mg/g.
Sulfated ash. Not more than 1.0 mg/g.
Loss on drying. Dry to constant mass at 105 °C; it loses not more than 5.0 mg/g.
Related substances. Carry out the test as described under 1.14.4 High-performance liquid chromatography, using a stainless steel column (15cm × 4.6mm) packed with particles of silica gel, the surface of which has been modified with chemically bonded octadecylsilyl groups (5μm). Prepare the following solution to be used as the mobile phase: dissolve 1.0 g of sodium octanesulfonate R and 0.4 g of tetrabutylammonium hydrogen sulfate R in 1000 ml of a mixture of 80 volumes of a 3.4 mg/ml solution of potassium dihydrogen phosphate R, the pH of the solution adjusted to 3.0 with phosphoric acid (~1440 g/l), 18 volumes of methanol R, and 2 volumes of tetrahydrofuran R.
Prepare the following solutions: for solution (A) dissolve 10 mg of Atenolol in 5 ml of mobile phase; for solution (B) dissolve 0.05 g of Atenolol in 0.10 ml of dimethyl sulfoxide R, if necessary applying gentle heat by placing the flask in a water-bath for a few seconds, and dilute with sufficient mobile phase to produce 25 ml; for solution (C) dilute 0.5 ml of solution A with sufficient mobile phase to produce 100 ml; and for solution (D) dissolve 0.05 g of atenolol for column validation RS in 0.10 ml of dimethyl sulfoxide R, if necessary applying gentle heat by placing the flask in a water-bath for a few seconds, and dilute with sufficient mobile phase to produce 25 ml.
Operate with a flow rate of 1.0 ml per minute. As a detector use an ultraviolet spectrophotometer set at a wavelength of about 226nm.
Inject 10 μl of solution C. Adjust the sensitivity of the system so that the height of the principal peak is at least 50% of the full scale of the recorder.
Inject 10 μl of solution D. The tracing obtained is similar to that of the specimen chromatogram provided with atenolol for column validation RS, where the peak due to the bis-ether precedes and is separated from the tertiary amine which normally appears as a doublet. If necessary, adjust the concentration of sodium octanesulfonate R in the mobile phase: a higher concentration would increase the retention time of the tertiary amine.
Inject alternately 10 μl each of solutions A and C. Continue the recording of the chromatogram for four times the retention time of the principal peak.
Measure the areas of the peak responses obtained in the chromatograms from solutions A and C, and calculate the content of the related substances as a percentage. In the chromatogram obtained with solution A, the area of any peak, other than the principal peak, is not greater than half the area of the principal peak obtained with solution C (0.25%). The sum of the areas of all the peaks, other than the principal peak, is not greater than that of the principal peak obtained with solution C (0.5%). Disregard any peak with an area less than 0.1 times that of the principal peak obtained with solution C. If the content of bisether in Atenolol is greater than 0.15%, repeat the chromatography with 10ml of solution B to confirm its compliance.
Assay. Dissolve about 0.2 g, accurately weighed, in 80 ml of glacial acetic acid R1, and titrate with perchloric acid (0.1 mol/l) VS as described under 2.6 Non-aqueous titration, Method A, determining the end-point potentiometrically.
Each ml of perchloric acid (0.1 mol/l) VS is equivalent to 26.63 mg of C14H22N2O3.