A:Infrared Absorption á197Fñ.

B:Ultraviolet Absorption á197Uñ—

System suitability solution— Prepare a solution of benzyl benzoate and USP Octinoxate RSin acetone containing about 50mg of each per mL.

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

Chromatographic system (see Chromatography á621ñ)— Proceed as directed in the Assay,but chromatograph the System suitability solution.

Procedure— Inject a volume (about 1µL)of the Test solutioninto the chromatograph,record the chromatogram,and measure the responses for all the peaks.Calculate the percentage of each impurity in the portion of Octinoxate taken by the formula: in which riis the peak response for each impurity;and rsis the sum of the responses 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 25mLof benzyl benzoate to a 500-mLvolumetric flask,dilute with acetone to volume,and mix.

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

Assay preparation— Transfer about 5mLof Octinoxate,accurately measured,to a 100-mLvolumetric flask,dilute with Internal standard solutionto volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The gas chromatograph is equipped with a flame-ionization detector and a 0.32-mm ×25-m column that contains coating G1.The carrier gas is helium,flowing at a rate of about 2mLper minute.The chromatograph is programmed as follows.Initially the temperature of the column is equilibrated at 80,then the temperature is increased to 300over a period of 10minutes,and maintained at 300for 10minutes.The injection port temperature is maintained at 250,and the detector is maintained at 300.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative retention times are about 0.68for benzyl benzoate and 1.0for octinoxate;the resolution,R,between benzyl benzoate and octinoxate is not less than 20;the column efficiency is not less than 65,000theoretical plates;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 1µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C18H26O3in the portion of Octinoxate taken by the formula: in which Cis the concentration,in mg per mL,of USP Octinoxate RSin the Standard preparation;and RUand RSare the peak response ratios of octinoxate to benzyl benzoate obtained from the Assay preparationand the Standard preparation,respectively.