Medium: 0.01Nhydrochloric acid;900mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Procedure— Determine the amount of C17H22N2O·C4H6O4dissolved by employing UVabsorption at the wavelength of maximum absorbance at about 262nm 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 Doxylamine Succinate RSin the same Medium.

Tolerances— Not less than 80%(Q)of the labeled amount of C17H22N2O·C4H6O4is dissolved in 30minutes.

Procedure for content uniformity— Transfer 1finely powdered Tablet to a 100-mLvolumetric flask containing 65mLof 0.1Nhydrochloric acid.Shake frequently during a 10-minute period,dilute with 0.1Nhydrochloric acid to volume,and mix.Allow the insoluble material to settle,and filter,discarding the first 20mLof the filtrate.Dilute a portion of the subsequent filtrate quantitatively and stepwise,if necessary,with 0.1Nhydrochloric acid to provide a solution containing approximately 25µg of doxylamine succinate per mL.Concomitantly determine the absorbances of this solution and of a Standard solution of USP Doxylamine Succinate RSin the same medium having a known concentration of about 25µg per mLin 1-cm cells at the wavelength of maximum absorbance at about 262nm,with a suitable spectrophotometer,using 0.1Nhydrochloric acid as the blank.Calculate the quantity,in mg,of C17H22N2O·C4H6O4in the Tablet taken by the formula: in which Tis the labeled quantity,in mg,of doxylamine succinate in the Tablet,Cis the concentration,in µg per mL,of USP Doxylamine Succinate RSin the Standard solution,Dis the concentration,in µg per mL,of doxylamine succinate in the solution from the Tablet,based on the labeled quantity per Tablet and the extent of dilution,and AUand ASare the absorbances of the solution from the Tablet and the Standard solution,respectively.

Mobile phase— Transfer 340mg of monobasic potassium phosphate,150mg of triethylamine hydrochloride,and 150mg of sodium lauryl sulfate to a 100-mLvolumetric flask,add 63mLof water,and mix.Dilute with acetonitrile to volume,filter,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Doxylamine Succinate RSin 0.1Mhydrochloric acid,and dilute quantitatively,and stepwise if necessary,with 0.1Mhydrochloric acid to obtain a solution having a known concentration of about 0.25mg per mL.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an amount of powder,equivalent to about 25mg of doxylamine succinate,accurately weighed,to a 100-mLvolumetric flask,dissolve in and dilute with 0.1Mhydrochloric acid to volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 262-nm detector and a 4.6-mm ×15-cm column that contains packing L7.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the tailing factor is not more than 2.5;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of doxylamine succinate (C17H22N2O·C4H6O4)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Doxylamine Succinate RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.