Identification—
Test specimen—
Transfer the final solution obtained from the titration in the Assay to a separator, add about 1 mL of 0.1 N sulfuric acid, and shake with 25 mL of ether. (Methyl red enters the ether phase.) Drain the aqueous layer into another separator, add 5 mL of 1 N sodium hydroxide, and shake with 10 mL of chloroform. Drain the chloroform layer into a small flask containing 2 g of anhydrous sodium sulfate, and swirl. Pour the chloroform solution through a small cotton pledget, pre-rinsed with chloroform, into a beaker, and evaporate to about 5 mL. Apply a few drops of the solution directly to a potassium bromide plate, and completely remove the chloroform by warming for 2 to 3 minutes under an IR lamp.
Assay—
Evaporate an accurately measured volume of Oral Solution, equivalent to about 250 mg of bromodiphenhydramine hydrochloride, to about half the original volume, using a suitable vacuum evaporator. Transfer the concentrated solution to a 250-mL separator, with the aid of sufficient warm water to bring the volume to the original volume. Add 20 g of sodium chloride, and shake until dissolved. Add 5 mL of 1 N sodium hydroxide, shake with 100 mL of ether, and drain the aqueous layer into a second separator containing 50 mL of ether. Shake, and discard the aqueous layer. Wash the ether solutions with two 20-mL portions of water, shaking each aqueous portion successively in the two separators, and then discard the aqueous solutions. Extract the ether solutions successively with 10.0 mL of 0.1 N sulfuric acid VS, followed by two 5-mL portions of water, and collect the aqueous extracts in a conical flask. Add
methyl red TS to the solution in the flask, and titrate the excess acid with 0.02 N sodium hydroxide VS. Perform a blank determination (see
Residual Titrations under
Titrimetry 
541
). Each mL of 0.1 N sulfuric acid is equivalent to 37.07 mg of bromodiphenhydramine hydrochloride (C
17H
20BrNO·HCl).
Bromodiphenhydramine Hydrochloride Elixir