Medium: 0.01 N hydrochloric acid; 900 mL.

Apparatus 2: 50 rpm.

Time: 30 minutes.

Procedure— Determine the amount of C17H22N2O·C4H6O4 dissolved by employing UV absorption at the wavelength of maximum absorbance at about 262 nm 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 RS in the same Medium.

Tolerances— Not less than 80% (Q) of the labeled amount of C17H22N2O·C4H6O4 is dissolved in 30 minutes.

Procedure for content uniformity— Transfer 1 finely powdered Tablet to a 100-mL volumetric flask containing 65 mL of 0.1 N hydrochloric acid. Shake frequently during a 10-minute period, dilute with 0.1 N hydrochloric acid to volume, and mix. Allow the insoluble material to settle, and filter, discarding the first 20 mL of the filtrate. Dilute a portion of the subsequent filtrate quantitatively and stepwise, if necessary, with 0.1 N hydrochloric acid to provide a solution containing approximately 25 µg of doxylamine succinate per mL. Concomitantly determine the absorbances of this solution and of a Standard solution of USP Doxylamine Succinate RS in the same medium having a known concentration of about 25 µg per mL in 1-cm cells at the wavelength of maximum absorbance at about 262 nm, with a suitable spectrophotometer, using 0.1 N hydrochloric acid as the blank. Calculate the quantity, in mg, of C17H22N2O·C4H6O4 in the Tablet taken by the formula: in which T is the labeled quantity, in mg, of doxylamine succinate in the Tablet, C is the concentration, in µg per mL, of USP Doxylamine Succinate RS in the Standard solution, D is 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 AU and AS are the absorbances of the solution from the Tablet and the Standard solution, respectively.

(Official January 1, 2007)

Mobile phase— Transfer 340 mg of monobasic potassium phosphate, 150 mg of triethylamine hydrochloride, and 150 mg of sodium lauryl sulfate to a 100-mL volumetric flask, add 63 mL of water, and mix. Dilute with acetonitrile to volume, filter, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

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

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

Chromatographic system (see Chromatography 621)—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 1.5 mL per 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 10 µL) of the Standard preparation and the Assay preparation into 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 C is the concentration, in mg per mL, of USP Doxylamine Succinate RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.