A: Dilute a volume of Injection, equivalent to about 50 mg of diphenhydramine hydrochloride, with 0.03 N sulfuric acid to 25 mL, and proceed as directed under Identification—Organic Nitrogenous Bases 181, beginning with “Transfer the liquid to a separator”: the Injection meets the requirements of the test.

B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.

(Official January 1, 2007)

Mobile phase, Standard preparation, System suitability solution, and Chromatographic system—Prepare as directed in the Assay under Diphenhydramine Hydrochloride.

Assay preparation— Transfer an accurately measured volume of Injection, equivalent to about 50 mg of diphenhydramine hydrochloride, to a 100-mL volumetric flask, dilute with water to volume, and mix.

Procedure— Proceed as directed for Procedure in the Assay under Diphenhydramine Hydrochloride. Calculate the quantity, in mg, of C17H21NO·HCl in each mL of the Injection taken by the formula: in which C is the concentration, in mg per mL, of USP Diphenhydramine Hydrochloride RS in the Standard preparation, V is the volume, in mL, of Injection taken, and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.