Medium: water;900mL.

Apparatus 2: 50rpm.

Time: 45minutes.

Procedure— Determine the amount of C19H24N2O3·HCl dissolved from UVabsorbances at the wavelength of maximum absorbance at about 302nm of filtered portions of the solution under test,suitably diluted with water,if necessary,in comparison with a Standard solution having a known concentration of USP Labetalol Hydrochloride RSin the same Medium.

Tolerances— Not less than 80%(Q)of the labeled amount of C19H24N2O3·HCl is dissolved in 45minutes.

Mobile phase ,Standard preparation,and Chromatographic system—Proceed as directed in the Assayunder Labetalol Hydrochloride.

Assay preparation— Transfer an accurately counted number of Tablets,equivalent to about 2000mg of labetalol hydrochloride,to a 500-mLvolumetric flask,add 200mLof water,and shake by mechanical means for 60minutes.Dilute with water to volume,and mix.Filter the solution through a filter of 0.5µm or finer porosity,discarding the first few mLof the filtrate.Transfer 10.0mLof the filtrate to a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Procedure— Separately inject equal volumes (about 5µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the area responses for the major peaks.Calculate the quantity,in mg,of labetalol hydrochloride (C19H24N2O3·HCl)in each Tablet taken by the formula: in which Cis the concentration,in mg per mL,of USP Labetalol Hydrochloride RSin the Standard preparation;Nis the number of Tablets taken;and rUand rSare the peak area responses obtained from the Assay preparationand the Standard preparation,respectively.