Solution: 25 µg per mL.

Medium: methanol.

Test solution— Use the Assay preparation.

Chromatographic system— Proceed as directed in the Assay. To evaluate the system suitability requirements, use the Standard preparation prepared as directed in the Assay.

Procedure— Inject a volume (about 1 µL) of the Test solution into the chromatograph, record the chromatogram, and measure all of the peak responses. Calculate the percentage of each impurity in the portion of Octocrylene taken by the formula: in which ri is the peak response for each impurity; and rs is the sum of the responses of 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.

Standard preparation— Dissolve an accurately weighed quantity of USP Octocrylene RS in acetone, and dilute quantitatively, and stepwise if necessary, with acetone to obtain a solution having a known concentration of about 21.0 mg per mL.

Assay preparation— Transfer about 2.1 g of Octocrylene, accurately weighed, to a 100-mL volumetric flask, dilute with acetone to volume, and mix.

Chromatographic system (see Chromatography 621)— The gas chromatograph is equipped with a flame-ionization detector and a 0.32-mm × 60-m column coated with a 0.25-µm film of G1. Helium is used as the carrier gas at a flow rate of about 6 mL per minute. The split ratio is 30:1. The chromatograph is programmed as follows. Initially the temperature of the column is equilibrated at 80; upon injection, the temperature is increased at a rate of 4 per minute to 280, and is held at 280 for 10 minutes. The injection port temperature is maintained at 300, and the detector temperature is maintained at 300. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the resolution, R, between the octocrylene and any other peak is not less than 1.0; 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 responses for the major peaks. Calculate the quantity, in mg, of C24H27NO2 in the portion of Octocrylene taken by the formula: in which C is the concentration, in mg per mL, of USP Octocrylene RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.