Ethylene Glycol Stearates
»Ethylene Glycol Stearates is a mixture of ethylene glycol monoesters and diesters of stearic and palmitic acids.It contains not less than 50.0percent of monoesters produced from the condensation of ethylene glycol and stearic acid of vegetable or animal origin.
Packaging and storage—
Preserve in tight containers.Store at room temperature and protect from light,freezing,and excessive heat.
Labeling—
Label it to indicate that it is intended for topical use only.
Identification—
A:
It meets the requirements of the test for Melting range.
B:
It meets the requirements of the test for Fatty acid composition.
Acid value á401ñ:
not more than 3.0,determined on 10.0g.
Iodine value á401ñ:
not more than 3.0.
Saponification value á401ñ:
between 170and 195,determined on 2.0g.
Fatty acid composition á401ñ—
The fatty acid fraction of it contains not less than 40.0%and not more than 60.0%of stearic acid;and the sum of the contents of palmitic and stearic acids is not less than 90.0%,as determined in the section Fatty Acid Composition.
Total ash á561ñ:
not more than 0.1%,determined on 1.0g.
Limit of free ethylene glycol—
Mobile phase and Chromatographic system—
Proceed as directed in the Assay.
Standard solutions—
Prepare four solutions by dissolving accurately weighed quantities of ethylene glycol in tetrahydrofuran and diluting each with tetrahydrofuran,as necessary,to obtain solutions having known concentrations of about 0.5,1.0,2.0,and 4.0mg per mL.
Test solution—
Use the Assay preparation,prepared as directed in the Assay.
Procedure—
Separately inject equal volumes (about 40µL)of the Standard solutionsand the Test solutioninto the chromatograph,record the chromatograms,and measure the responses for the ethylene glycol peaks.Plot the ethylene glycol peak responses obtained versus the concentration,in mg per mL,of ethylene glycol in the Standard solutions.From the standard curve so obtained,determine the ethylene glycol concentration,C,in mg per mL,in the Test solution.Calculate the percentage of free ethylene glycol in the portion of Ethylene Glycol Stearates taken by the formula:
500(C/W),
in which Cis as obtained above;and Wis the amount,in mg,of Ethylene Glycol Stearates taken to prepare the Test solution:not more than 5.0%of free ethylene glycol is found.
Assay—
Mobile phase:
tetrahydrofuran.
Assay preparation—
Transfer about 200mg of Ethylene Glycol Stearates,accurately weighed,to a 5-mLvolumetric flask,dissolve in and dilute with tetrahydrofuran to volume,and mix.
Chromatographic system (see Chromatography á621ñ)—
The liquid chromatograph is equipped with a refractive index detector and a 7.5-mm ×60-cm column containing 5-µm 100Åpacking L21.The column and the detector temperatures are maintained at 40
.[NOTE—Two or three 7.5-mm ×30-cm L21columns may be used in place of the one 60-cm column provided that system suitability requirements are met;and the column temperature may be lowered to ambient temperature,although working at 40provides stable separation conditions and ensures better sample solubility.]The flow rate is about 1mLper minute.Chromatograph the Assay preparation,and record the peak responses as directed for Procedure:the relative retention times are about 1.0for ethylene glycol,0.83for monoesters,and 0.76for diesters;and the relative standard deviation for replicate injections determined from the monoesters peak is not more than 2.0%.
.[NOTE—Two or three 7.5-mm ×30-cm L21columns may be used in place of the one 60-cm column provided that system suitability requirements are met;and the column temperature may be lowered to ambient temperature,although working at 40provides stable separation conditions and ensures better sample solubility.]The flow rate is about 1mLper minute.Chromatograph the Assay preparation,and record the peak responses as directed for Procedure:the relative retention times are about 1.0for ethylene glycol,0.83for monoesters,and 0.76for diesters;and the relative standard deviation for replicate injections determined from the monoesters peak is not more than 2.0%.
Procedure—
Inject about 40µLof the Assay preparation into the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the percentage of free fatty acids,E,in the portion of Ethylene Glycol Stearates taken by the formula:
IA×270/561.1,
in which IAis the acid value,determined in the test for Acid value.Calculate the percentage of monoesters in the portion of Ethylene Glycol Stearates taken by the formula:
[rM/(rM+rD)](100–D–E),
in which rMis the peak response due to monoesters;rDis the peak response due to diesters;Dis the percentage of free ethylene glycol in the portion of Ethylene Glycol Stearates taken,as determined in the test for Limit of free ethylene glycol;and Eis as defined above.
Auxiliary Information—
Staff Liaison:Elena Gonikberg,Ph.D.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 3005
Pharmacopeial Forum:Volume No.30(3)Page 974
Phone Number:1-301-816-8251