U.S. PHARMACOPEIA

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Diethylene Glycol Stearates
» Diethylene Glycol Stearates is a mixture of diethylene glycol monoesters and diesters of stearic and palmitic acids. It contains not less than 45.0 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 and vaginal 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.
Melting range, Class II 741: between 43 and 50.
Acid value 401: not more than 4.0, determined on 10.0 g.
Iodine value 401: not more than 3.0.
Saponification value 401: between 150 and 170, 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, determined as directed in the chapter, is not less than 90.0%.
Total ash 561: not more than 0.1%, determined on 1.0 g.
Limit of free diethylene glycol—
Mobile phase and Chromatographic system— Proceed as directed in the Assay.
Standard solutions— Prepare four solutions by dissolving accurately weighed quantities of diethylene 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 diethylene glycol peaks. Plot the diethylene glycol peak responses obtained versus the concentration, in mg per mL, of diethylene glycol in the Standard solutions. From the standard curve so obtained, determine the diethylene glycol concentration, C, in mg per mL, in the Test solution. Calculate the percentage of free diethylene glycol in the portion of Diethylene Glycol Stearates taken by the formula:
500(C/W),
in which C is as obtained above; and W is the amount, in mg, of Diethylene Glycol Stearates taken to prepare the Test solution: not more than 8.0% of free diethylene glycol is found.
Assay—
Mobile phase: tetrahydrofuran.
Assay preparation— Transfer about 200 mg of Diethylene 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)— Prepare as directed in the Assay under Ethylene Glycol Stearates. Chromatograph the Assay preparation, and record the peak responses as directed for Procedure: the relative retention times are about 1.0 for diethylene glycol, 0.84 for monoesters, and 0.78 for diesters; and the relative standard deviation for replicate injections determined from the monoesters peak is not more than 2.0%.
Procedure— Inject a volume (about 40 µL) of the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the percentage content of free fatty acids, E, by the formula:
IA × 270/561.1,
in which IA is the acid value, determined in the test for Acid value. Calculate the percentage of monoesters in the portion of Diethylene Glycol Stearates taken by the formula:
[(rM /(rM + rD )](100 – D – E),
in which rM is the peak response for the monoesters; rD is the peak response for the diesters; D is the percentage of free diethylene glycol in the portion of Diethylene Glycol Stearates taken, as determined in the test for Limit of free diethylene glycol; and E is as defined above.
Auxiliary Information— Staff Liaison : Catherine Sheehan, B.Sc., Scientist
Expert Committee : (EM105) Excipient Monographs 1
USP29–NF24 Page 3327
Pharmacopeial Forum : Volume No. 30(3) Page 974
Phone Number : 1-301-816-8262