A: Infrared Absorption 197F.

B: Ultraviolet Absorption 197U—

Test solution— Transfer about 5 mL of Octinoxate to a 100-mL volumetric flask, dilute with acetone to volume, and mix.

Chromatographic system (see Chromatography 621)— Proceed as directed in the Assay.

Procedure— Inject a volume (about 1 µL) of the Test solution into the chromatograph, record the chromatogram, and measure the areas for all the peaks. Calculate the percentage of each impurity in the portion of Octinoxate taken by the formula: in which ri is the peak area for each impurity; and rs is the sum of the areas for all the peaks: not more than 0.5% of any individual impurity is found; and not more than 2.0% of total impurities is found.

Internal standard solution— Transfer about 25 mL of benzyl benzoate to a 500-mL volumetric flask, dilute with acetone to volume, and mix.

Standard preparation— Dilute an accurately measured quantity of USP Octinoxate RS quantitatively, and stepwise if necessary, with Internal standard solution to obtain a solution having a known concentration of about 50 mg per mL.

Assay preparation— Transfer about 5 mL of Octinoxate, accurately measured, to a 100-mL volumetric flask, dilute with Internal standard solution to volume, and mix.

Chromatographic system (see Chromatography 621)— The gas chromatograph is equipped with a flame-ionization detector, a 0.32-mm × 25-m column that contains coating G1, and a split injection system with a split ratio of about 85:1. The carrier gas is helium, flowing at a rate of about 2 mL per minute. The chromatograph is programmed as follows. Initially the temperature of the column is equilibrated at 80, then the temperature is increased to 300 over a period of 10 minutes, and maintained at 300 for 10 minutes. The injection port temperature is maintained at 250, and the detector temperature is maintained at 300. Chromatograph the Standard preparation, and record the peak areas as directed for Procedure: the relative retention times are about 0.68 for benzyl benzoate and 1.0 for octinoxate; the resolution, R, between benzyl benzoate and octinoxate is not less than 20; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 1 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the areas for the major peaks. Calculate the quantity, in mg, of C18H26O3 in the portion of Octinoxate taken by the formula: in which C is the concentration, in mg per mL, of USP Octinoxate RS in the Standard preparation; and RU and RS are the peak area ratios of octinoxate to benzyl benzoate obtained from the Assay preparation and the Standard preparation, respectively.