Medium: water; 900 mL.

Apparatus 2: 50 rpm.

Time: 30 minutes.

Procedure— Determine the amount of C12H20N2O3S·HCl dissolved by employing UV absorption at the wavelength of maximum absorbance at about 230 nm on filtered portions of the solution under test, in comparison with a Standard solution having a known concentration of USP Sotalol Hydrochloride RS in the same Medium.

Tolerances— Not less than 80% (Q) of the labeled amount of C12H20N2O3S·HCl is dissolved in 30 minutes.

Phosphate buffer— Dissolve 6.8 g of monobasic potassium phosphate in about 800 mL of water. Dilute with water to 1000 mL, and mix.

Mobile phase— Prepare a filtered and degassed mixture of Phosphate buffer and acetonitrile (9:1).

Internal standard solution— Transfer about 1.8 g of caffeine, accurately weighed, to a 1000-mL volumetric flask. Dissolve in and dilute with water to volume, and mix.

Standard preparation— Transfer about 80 mg of USP Sotalol Hydrochloride RS, accurately weighed, to a 25-mL volumetric flask. Add 2.5 mL of 1 N hydrochloric acid, dissolve in and dilute with water to volume, mix, and filter. Transfer 10.0 mL of the filtrate and 25.0 mL of the Internal standard solution to a 200-mL volumetric flask. Dilute with water to volume, and mix.

Assay preparation— Transfer an appropriate number of Tablets, equivalent to about 800 mg of sotalol hydrochloride, to a 250-mL volumetric flask. Add 25 mL of 1 N hydrochloric acid, and swirl. Dilute with water to about three-fourths of the volume of the flask, and shake for 15 minutes. Dilute with water to volume, mix, and filter. Transfer 10.0 mL of this solution and 25.0 mL of the Internal standard solution to a 200-mL volumetric flask. Dilute with water to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 238-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The flow rate is about 1.5 mL per minute. Chromatograph the Standard preparation, and record the peak areas as directed for Procedure: the relative retention times for sotalol and caffeine are about 1.0 and 2.0, respectively; the resolution, R, between caffeine and sotalol is not less than 6.0; and the relative standard deviation for replicate injections, determined from peak area ratios, is not more than 2.0%.

Procedure— Separately inject equal volumes (about 25 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the areas for the major peaks. Calculate the quantity, in mg, of sotalol hydrochloride (C12H20N2O3S·HCl) in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Sotalol Hydrochloride RS in the Standard preparation; and RU and RS are the peak area ratios of sotalol to caffeine obtained from the Assay preparation and the Standard preparation, respectively.