Ethylene Glycol Stearates
(eth' i leen glye' kol steer' ates).
» Ethylene Glycol Stearates is a mixture of ethylene glycol monoesters and diesters of stearic and palmitic acids. It contains not less than 50.0 percent of monoesters produced from the condensation of ethylene glycol and stearic acid of vegetable or animal origin.
Packaging and storage Preserve in tight containers. No storage requirements specified.
Labeling Label it to indicate that it is intended for topical use only.
A: It meets the requirements of the test for Melting range.
B: It meets the requirements of the test for Fatty acid composition.
Melting range, Class II 741: between 54 and 60.
Acid value 401: not more than 3.0, determined on 10.0 g.
Iodine value 401: not more than 3.0.
Saponification value 401: between 170 and 195, determined on 2.0 g.
Fatty acid composition 401 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 561: not more than 0.1%, determined on 1.0 g.
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 4.0 mg per mL.
Test solution Use the Assay preparation, prepared as directed in the Assay.
Procedure Separately inject equal volumes (about 40 µL) of the Standard solutions and the Test solution into 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 C is as obtained above; and W is 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.
Mobile phase: tetrahydrofuran.
Assay preparation Transfer about 200 mg of Ethylene Glycol Stearates, accurately weighed, to a 5-mL volumetric flask, dissolve in and dilute with tetrahydrofuran to volume, and mix.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a refractive index detector and a 7.5-mm × 60-cm column containing 5-µm 100 packing L21. The column and the detector temperatures are maintained at 40. [noteTwo or three 7.5-mm × 30-cm L21 columns 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 40 provides stable separation conditions and ensures better sample solubility. ] The flow rate is about 1 mL per minute. Chromatograph the Assay preparation, and record the peak responses as directed for Procedure: the relative retention times are about 1.0 for ethylene glycol, 0.83 for monoesters, and 0.76 for diesters; and the relative standard deviation for replicate injections determined from the monoesters peak is not more than 2.0%.
Procedure Inject about 40 µL of 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 × 270/561.1in which IA is 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 rM is the peak response due to monoesters; rD is the peak response due to diesters; D is 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 E is as defined above.