Solvent: dimethyl sulfoxide.

System suitability solution— Dissolve accurately weighed quantities of USP Octyldodecanol RSand USP Stearyl Alcohol RSin alcohol to obtain a solution having known concentrations of about 9mg per mLand 1mg per mL,respectively.

Assay preparation— Dissolve 90mg of Octyldodecanol in 10.0mLof alcohol,and mix.

Chromatographic system (see Chromatography á621ñ)—The gas chromatograph is equipped with a flame-ionization detector and a 2-mm ×2-m column packed with 3%liquid phase G2on support S1A.The carrier gas is nitrogen.The column temperature is programmed as follows.Initially it is equilibrated at about 80,then increased at a rate of 6per minute to 300.The detector and the injection port temperatures are both maintained at about 280.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the resolution,R,between octyldodecanol and stearyl alcohol is not less than 4.0;and the relative standard deviation for replicate injections is not more than 1.5%.

Procedure— Inject about 2µLof the Assay preparationinto the chromatograph,record the chromatogram,and measure the areas for the major peaks.Calculate the percentage of C20H42Oin the portion of Octyldodecanol taken by the formula: in which rUis the peak area for octyldodecanol obtained from the Assay preparation;and rsis the sum of the areas of all the peaks except the solvent peak.