Medium: 0.1 N hydrochloric acid; 900 mL.

Apparatus 2: 50 rpm.

Time: 60 minutes.

Procedure— Determine the amount of C18H22N2·HCl dissolved by employing UV absorption at the wavelength of maximum absorbance at about 251 nm on filtered portions of the solution under test, suitably diluted with Dissolution Medium, if necessary, in comparison with a Standard solution having a known concentration of USP Desipramine Hydrochloride RS in the same Medium.

Tolerances— Not less than 75% (Q) of the labeled amount of C18H22N2·HCl is dissolved in 60 minutes.

Procedure for content uniformity— Transfer 1 finely powdered Tablet to a 100-mL volumetric flask, add 50 mL of 0.1 N hydrochloric acid, and shake by mechanical means for 15 minutes. Dilute with 0.1 N hydrochloric acid to volume, mix, and filter, discarding the first 20 mL of the filtrate. Dilute a portion of the subsequent filtrate quantitatively and stepwise with 0.1 N hydrochloric acid to provide a solution containing approximately 25 µg of desipramine hydrochloride per mL. Concomitantly determine the absorbances of this solution and a Standard solution of USP Desipramine Hydrochloride 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 251 nm, with a suitable spectrophotometer, using 0.1 N hydrochloric acid as the blank. Calculate the quantity, in mg, of C18H22N2·HCl in the tablet taken by the formula: in which T is the labeled quantity, in mg, of desipramine hydrochloride in the Tablet, C is the concentration, in µg per mL, of USP Desipramine Hydrochloride RS in the Standard solution, D is the concentration, in µg per mL, of desipramine hydrochloride in the test solution, based upon 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)

Standard preparation— Dissolve a suitable quantity of USP Desipramine Hydrochloride RS, accurately weighed, in 0.1 N hydrochloric acid, and dilute quantitatively and stepwise with the same solvent to obtain a solution having a known concentration of about 25 µg per mL.

Assay preparation— Finely powder a number of Tablets, equivalent to about 0.5 g of desipramine hydrochloride, and transfer the powder to a 500-mL volumetric flask with the aid of 100 mL of 0.1 N hydrochloric acid. Add 150 mL of the 0.1 N acid to the mixture, insert the stopper, and shake by mechanical means for 30 minutes. Dilute with 0.1 N hydrochloric acid to volume, mix, and filter, discarding the first 10 mL of the filtrate. Transfer 5.0 mL of the subsequent filtrate to a 200-mL volumetric flask, dilute with 0.1 N hydrochloric acid to volume, and mix.

Procedure— Transfer 15.0 mL each of the Standard preparation and the Assay preparation, respectively, to separate glass-stoppered, 50-mL centrifuge tubes, and to each tube add 2 mL of 2.5 N sodium hydroxide and 15.0 mL of cyclohexane suitable for use in UV spectrophotometry. Insert the stoppers, shake the tubes by mechanical means for 30 minutes, and centrifuge at about 1500 rpm until the clear phases separate (5 to 10 minutes). Concomitantly determine the absorbances of the cyclohexane extracts in 1-cm cells at the wavelength of maximum absorbance at about 255 nm, with a suitable spectrophotometer, using cyclohexane suitable for use in UV spectrophotometry as the blank. Calculate the quantity, in mg, of C18H22N2·HCl in the portion of Tablets taken by the formula: in which C is the concentration, in µg per mL, of USP Desipramine Hydrochloride RS in the Standard preparation, and AU and AS are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.