Cetostearyl Alcohol
»Cetostearyl Alcohol contains not less than 40.0percent of stearyl alcohol (C18H38O),and the sum of the stearyl alcohol content and the cetyl alcohol (C16H34O)content is not less than 90.0percent.
Packaging and storage—
Preserve in well-closed containers.
Identification—
The retention times of the major peaks in the chromatogram of the Assay preparationcorrespond to those 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 4.
Hydroxyl value á401ñ—
Place about 2g,accurately weighed,in a dry,glass-stoppered,250-mLflask,add 2mLof pyridine,then add 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 with 1Nsodium hydroxide VSto a permanent pink endpoint,shaking the flask vigorously toward the end of the titration in order to maintain the contents in an emulsified condition.Perform a blank determination 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 specimen under test and that consumed in the blank test,multiplied by 56.1,and the result divided by the weight,in g,of the Cetostearyl Alcohol used,represents the hydroxyl value of the Cetostearyl Alcohol.The hydroxyl value is between 208and 228.
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 with 1Nsodium hydroxide VSto a permanent pink endpoint,shaking the flask vigorously toward the end of the titration in order to maintain the contents in an emulsified condition.Perform a blank determination 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 specimen under test and that consumed in the blank test,multiplied by 56.1,and the result divided by the weight,in g,of the Cetostearyl Alcohol used,represents the hydroxyl value of the Cetostearyl Alcohol.The hydroxyl value is between 208and 228.
Assay—
System suitability solution—
Dissolve accurately weighed quantities of USP Cetyl Alcohol RSand USP Stearyl Alcohol RSin alcohol to obtain a solution having a known concentration of about 5mg of each per mL.
Assay preparation—
Dissolve 100mg of Cetostearyl 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 column temperature is maintained at about 205,the injection port at about 275,and the detector 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 at about 275,and the detector 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.Separately calculate the percentages of cetyl alcohol (C16H34O)and stearyl alcohol (C18H38O)in the portion of Cetostearyl Alcohol taken by the formula:
100(rU/rs),
in which rUis the peak area obtained from cetyl alcohol or stearyl alcohol;and rsis the sum of the areas of all the peaks,except the solvent peak.
Auxiliary Information—
Staff Liaison:Daniel K.Bempong,Ph.D.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 2985
Pharmacopeial Forum:Volume No.28(4)Page 1211
Phone Number:1-301-816-8143