Medium: water; 500 mL.

Apparatus 1: 100 rpm.

Time: 45 minutes.

Procedure— Determine the amount of C16H19BrN2·C4H4O4 dissolved from UV absorbances at the wavelength of maximum absorbance at about 264 nm on filtered portions of the solution under test, suitably diluted with 3 N hydrochloric acid, using 5-cm cuvettes, in comparison with a Standard solution having a known concentration of USP Brompheniramine Maleate RS in the same Medium.

Tolerances— Not less than 75% (Q) of the labeled amount of C16H19BrN2·C4H4O4 is dissolved in 45 minutes.

(Official January 1, 2007)

Standard preparation— Dissolve an accurately weighed quantity of USP Brompheniramine Maleate RS in water, and dilute quantitatively with water to obtain a solution having a known concentration of about 160 µg per mL. Transfer 25.0 mL of this solution to a separator containing 25 mL of water, mix, and proceed as directed under Assay preparation, beginning with “adjust with sodium hydroxide solution (1 in 10) to a pH of 11.” The concentration of USP Brompheniramine Maleate RS in the Standard preparation is about 20 µg per mL.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Weigh accurately a portion of the powder, equivalent to about 4 mg of brompheniramine maleate, mix with 50 mL of water for 10 minutes, adjust with sodium hydroxide solution (1 in 10) to a pH of 11, and cool to room temperature. Extract the mixture with two 75-mL portions of solvent hexane, and combine the extracts in a second separator. Extract the solvent hexane solution with three 50-mL portions of dilute hydrochloric acid (1 in 120), combining the acid extracts in a 200-mL volumetric flask. Add dilute hydrochloric acid (1 in 120) to volume, and mix.

Procedure— Concomitantly determine the absorbances of the Assay preparation and the Standard preparation, in 1-cm cells at the wavelength of maximum absorbance at about 264 nm, with a suitable spectrophotometer, using dilute hydrochloric acid (1 in 120) as the blank. Calculate the quantity, in mg, of C16H19Br N2·C4H4O4 in the portion of Tablets taken by the formula: in which C is the concentration, in µg per mL, of USP Brompheniramine Maleate RS in the Standard preparation; and AU and AS are the absorbances of the Assay preparation and the Standard preparation, respectively.