NOTE—Throughout the following procedures,protect test or assay specimens,the Reference Standard,and solutions containing them,by conducting the procedures without delay,under subdued light,or using low-actinic glassware.

Medium: 0.01Nhydrochloric acid;900mL.

Apparatus 1: 100rpm.

Time: 45minutes.

Procedure— Determine the amount of C17H20N2S·HCl dissolved by employing UVabsorption at the wavelength of maximum absorbance at about 249nm on filtered portions of the solution under test,suitably diluted with Dissolution Medium,in comparison with a Standard solution having a known concentration of USP Promethazine Hydrochloride RSin the same Medium.

Tolerances— Not less than 75%(Q)of the labeled amount of C17H20N2S·HCl is dissolved in 45minutes.

Procedure for content uniformity— Transfer 1finely powdered Tablet to a 100-mLvolumetric flask,add 50mLof citric acid solution (1in 100),and shake by mechanical means for 15minutes.Dilute with citric acid solution (1in 100)to volume,and centrifuge about 50mLof the mixture.Dilute an accurately measured portion of the clear solution,equivalent to 5mg of promethazine hydrochloride,quantitatively with citric acid solution (1in 100)to 100mL.Concomitantly determine the absorbance of this solution and a Standard solution of USP Promethazine Hydrochloride RSin the same medium,having a known concentration of about 50µg per mL,in 1-cm cells at the wavelength of maximum absorbance at about 298nm,with a suitable spectrophotometer,using citric acid solution (1in 100)as the blank.Calculate the quantity,in mg,of C17H20N2S·HCl in the Tablet by the formula: in which Tis the labeled quantity,in mg,of promethazine hydrochloride in the Tablet;Dis the concentration,in µg per mL,of promethazine hydrochloride in the test solution based on the labeled quantity per Tablet and the extent of dilution;Cis the concentration,in µg per mL,of USP Promethazine Hydrochloride RSin the Standard solution;and AUand ASare the absorbances of the solution from the Tablet and the Standard solution,respectively.

Buffered palladium chloride solution— Transfer 500mg of palladium chloride to a 250-mLbeaker,add 5mLof hydrochloric acid,and warm on a steam bath.Add 200mLof hot water in small quantities while stirring until solution is complete.Cool,dilute with water to 500mL,and mix.Transfer 25mLof this solution to a 500-mLvolumetric flask.Add 50mLof 1Nsodium acetate and 48mLof 1Nhydrochloric acid,dilute with water to volume,and mix.

Standard preparation— Transfer about 31mg of USP Promethazine Hydrochloride RS,accurately weighed,to a low-actinic 250-mLvolumetric flask.Dissolve in 0.1Nhydrochloric acid,dilute with 0.1Nhydrochloric acid to volume,and mix.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 6.25mg of promethazine hydrochloride,to a low-actinic 125-mLseparator.Add 20mLof saturated potassium chloride solution,10mLof 1Nsodium hydroxide,and 10mLof methanol,and extract the promethazine with three 20-mLportions of n-heptane.Filter the heptane extracts through anhydrous sodium sulfate and collect them in a low-actinic 125-mLseparator.Extract the promethazine from the n-heptane solution with three 15-mLportions of 0.1Nhydrochloric acid,collect the acid extracts in a low-actinic 50-mLvolumetric flask,dilute with 0.1Nhydrochloric acid to volume,and mix.

Procedure— Into separate test tubes,pipet 2-mLportions of the Standard preparation,the Assay preparation,and 0.1Nhydrochloric acid to provide a blank.Add 3.0mLof Buffered palladium chloride solutionto each tube,and mix.Concomitantly determine the absorbances of the solutions at the wavelength of maximum absorbance at about 470nm,using a suitable spectrophotometer,and using the blank in the reference cell.Calculate the quantity,in mg,of promethazine hydrochloride (C17H20N2S·HCl)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Promethazine Hydrochloride RSin the Standard preparation;and AUand ASare the absorbances of the solutions from the Assay preparationand the Standard preparation,respectively.