A: Prepare a solution in methanol to contain 10 mg of benzoyl peroxide per mL. Apply 5 µL of this solution and 5 µL of a freshly prepared Standard solution of Hydrous Benzoyl Peroxide, previously subjected to the Assay, in methanol containing 10 mg per mL on a line parallel to and about 2.5 cm from the bottom of a thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture. Place the plate in a developing chamber containing, and equilibrated with, a mixture of toluene, dichloromethane, and glacial acetic acid (50:2:1). Develop the chromatogram until the solvent front has moved about three-fourths of the length of the plate. Remove the plate, and allow the solvent to evaporate. Observe the plate under short-wavelength UV light: the RF value of the principal spot obtained from the solution under test corresponds to that obtained from the Standard solution.

B: Dissolve an accurately weighed quantity in acetonitrile to obtain a solution containing 0.32 mg of benzoyl peroxide per mL. Chromatograph this test solution and a freshly prepared Standard solution of Hydrous Benzoyl Peroxide, previously subjected to the Assay, in acetonitrile containing 0.32 mg per mL as directed in the test for Related compounds under Benzoyl Peroxide Gel: the solution under test exhibits a major peak for benzoyl peroxide, the retention time of which corresponds to that exhibited by the Standard solution.

(Official January 1, 2007)