Stearyl Alcohol
1-Octadecanol.
1-Octadecanol [112-92-5].
»Stearyl Alcohol contains not less than 90.0percent of stearyl alcohol (C18H38O),the remainder consisting chiefly of related alcohols.
Packaging and storage—
Preserve in well-closed containers.
Identification—
The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the System suitability solution,as obtained in the Assay.
Acid value á401ñ:
not more than 2.
Iodine value á401ñ:
not more than 2.
Hydroxyl value—
Place about 2g,accurately weighed,in a dry,glass-stoppered,250-mLflask,and add 2mLof pyridine,followed by 10mLof toluene.To the mixture add 10.0mLof a solution of acetyl chloride,prepared by mixing 10mLof acetyl chloride with 90mLof toluene.Insert the stopper in the flask,and immerse in a water bath heated at 60
to 65for 20minutes.Add 25mLof water,again insert the stopper in the flask,and shake vigorously for several minutes to decompose the excess acetyl chloride.Add 0.5mLof phenolphthalein TS,and titrate to a permanent pink endpoint with 1Nsodium hydroxide VS,shaking the flask vigorously toward the end of the titration to maintain the contents in an emulsified condition.Perform a blank test with the same quantities of the same reagents and in the same manner.The difference between the number of mLof 1Nsodium hydroxide consumed in the test with the sample and that consumed in the blank test,multiplied by 56.1,and the result divided by the weight,in g,of the Stearyl Alcohol used,represents the hydroxyl value of the Stearyl Alcohol,which is between 195and 220.
to 65for 20minutes.Add 25mLof water,again insert the stopper in the flask,and shake vigorously for several minutes to decompose the excess acetyl chloride.Add 0.5mLof phenolphthalein TS,and titrate to a permanent pink endpoint with 1Nsodium hydroxide VS,shaking the flask vigorously toward the end of the titration to maintain the contents in an emulsified condition.Perform a blank test with the same quantities of the same reagents and in the same manner.The difference between the number of mLof 1Nsodium hydroxide consumed in the test with the sample and that consumed in the blank test,multiplied by 56.1,and the result divided by the weight,in g,of the Stearyl Alcohol used,represents the hydroxyl value of the Stearyl Alcohol,which is between 195and 220.
Assay—
System suitability solution—
Dissolve accurately weighed quantities of USP Stearyl Alcohol RSand USP Cetyl Alcohol RSin dehydrated alcohol to obtain a solution containing about 9mg per mLand 1mg per mL,respectively.
Assay preparation—
Dissolve 100mg of Stearyl Alcohol in 10.0mLof dehydrated alcohol,and mix.
Chromatographic system(see Chromatography á621ñ)—
The gas chromatograph is equipped with a flame-ionization detector and a 3-mm ×2-m column packed with 10%liquid phase G2on support S1A.The carrier gas is helium.The temperature of the column is maintained at about 205,the injection port temperature is maintained at about 275,and the detector is maintained at about 250.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the resolution,R,between cetyl alcohol and stearyl alcohol is not less than 4.0;and the relative standard deviation for replicate injections is not more than 1.5%.
,the injection port temperature is maintained at about 275,and the detector is maintained at about 250.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the resolution,R,between cetyl alcohol 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 C18H38Oin the portion of Stearyl Alcohol taken by the formula:
100(rU/rs),
in which rUis the peak area for stearyl alcohol obtained from the Assay preparation;and rsis the sum of the areas of all the peaks except the solvent peak.
Auxiliary Information—
Staff Liaison:Catherine Sheehan,B.Sc.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 3092
Pharmacopeial Forum:Volume No.29(6)Page 2021
Phone Number:1-301-816-8262