A: Dilute a quantity of Lotion with acetone to obtain a solution having a concentration of benzoyl peroxide equivalent to 10 mg per mL, and proceed with the solution so obtained as directed in the Identification test A under Hydrous Benzoyl Peroxide, beginning with “Apply 5 µL of this solution.” The solution responds to the test.

B: It responds to the Identification test under Benzoyl Peroxide Gel.

Solution A, Solution B, Mobile phase, Standard preparation A, Standard preparation B, Standard preparation C, Standard preparation D, System suitability solution, and Chromatographic system— Proceed as directed in the test for Related compounds under Benzoyl Peroxide Gel.

Test preparation— Transfer an accurately weighed quantity of Lotion, equivalent to about 100 mg of benzoyl peroxide, to a 50-mL volumetric flask, add 25 mL of acetonitrile, shake vigorously to disperse the specimen, sonicate for 5 minutes, dilute with acetonitrile to volume, mix, and filter.

Procedure— Proceed with Lotion as directed for Procedure in the test for Related compounds under Benzoyl Peroxide Gel: it meets the limits stated.

(Official January 1, 2007)

Mobile phase , Internal standard solution, Standard preparation, and Chromatographic system—Proceed as directed in the Assay under Benzoyl Peroxide Gel.

Assay preparation— Prepare as directed for Assay preparation in the Assay under Benzoyl Peroxide Gel, using Lotion.

Procedure— Proceed as directed for Procedure in the Assay under Benzoyl Peroxide Gel. Calculate the quantity, in mg, of C14H10O4 in the portion of Lotion taken by the formula: in which C is the concentration, in mg per mL, of benzoyl peroxide in the Standard preparation; and RU and RS are the ratios of benzoyl peroxide peak response to ethyl benzoate peak response obtained from the Assay preparation and the Standard preparation, respectively.