Diethylene Glycol Stearates

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION

Diethylene Glycol Stearates is a mixture of diethylene glycol monoesters and diesters of stearic and palmitic acids. It contains NLT 45.0% of monoesters produced from the condensation of diethylene (_{RB 1-Jun-2022)} glycol and stearic acid of vegetable or animal origin.

2 IDENTIFICATION

A. It meets the requirements in Specic Tests for Melting Range or Temperature 〈741〉, Class II.

B. It meets the requirements in Specic Tests for Fats and Fixed Oils 〈401〉, Fatty Acid Composition.

3 ASSAY

Procedure

Mobile phase: Tetrahydrofuran 

Sample solution: 40 mg/mL of Diethylene Glycol Stearates in tetrahydrofuran 

3.1 Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: Refractive index 

Column: 7.5-mm × 60-cm; containing 5-µm 100Å packing L21. [Note—Two or three 7.5-mm × 30-cm L21 columns may be used in place of the 60-cm column, provided that System suitability requirements are met.] 

Temperatures 

Detector: 40° 

Column: 40°. [Note—The column temperature may be lowered to ambient temperature, although working at 40° provides stable separation conditions and ensures better sample solubility.] 

Flow rate: 1 mL/min 

Injection volume: 40 µL 

3.2 System suitability 

Sample: Sample solution 

[Note—The relative retention times for diesters, monoesters, and diethylene glycol are 0.78, 0.84, and 1.0, respectively.] Suitability requirements 

Relative standard deviation: NMT 2.0% for the monoesters peak 

3.3 Analysis 

Sample: Sample solution 

Calculate the percentage of free fatty acids, E, in the portion of Diethylene Glycol Stearates taken: 

E = I_A × 270/561.1 

I_A = acid value, determined in Specific Tests for Fats and Fixed Oils 〈401〉, Acid Value (Free Fatty Acids) 

Calculate the percentage of monoesters in the portion of Sample taken: 

Result = [r_M /(r_M + r_D )] × (100 − D − E)  

r_M = peak response for the monoesters 

r_D = peak response for the diesters 

D = percentage of free diethylene glycol in the portion of Diethylene Glycol Stearates taken, as determined in Impurities for Limit of Free Diethylene Glycol 

Acceptance criteria: NLT 45.0% of monoesters

4 IMPURITIES

Limit of Free Diethylene Glycol

Mobile phase, Sample solution, Chromatographic system, and System suitability: Proceed as directed in the Assay. Standard solution A: 0.5 mg/mL of diethylene glycol in tetrahydrofuran

Standard solution B: 1.0 mg/mL of diethylene glycol in tetrahydrofuran

Standard solution C: 2.0 mg/mL of diethylene glycol in tetrahydrofuran

Standard solution D: 4.0 mg/mL of diethylene glycol in tetrahydrofuran

Analysis

Samples: Sample solution and Standard solutions

Plot the diethylene glycol peak responses obtained versus the concentration of diethylene glycol in the Standard solutions. From the standard curve so obtained, determine the diethylene glycol concentration in the sample.

Calculate the percentage of free diethylene glycol in the portion of sample taken:

Result = (C/C_U ) × 100

C = concentration of diethylene glycol, determined from the standard curve (mg/mL)

C_U = concentration of the Sample solution (mg/mL)

Acceptance criteria: NMT 8.0%

5 SPECIFIC TESTS

Melting Range or Temperature 〈741〉, Class II: 43°–50°

Fats and Fixed Oils 〈401〉, Acid Value (Free Fatty Acids)

Sample: 10.0 g

Acceptance criteria: NMT 4.0

Fats and Fixed Oils 〈401〉, Iodine Value: NMT 3.0

Change to read:

Fats and Fixed Oils 〈401〉, Saponification value

Sample: 2.0 g

Acceptance criteria: 150–180 (RB 1-Jun-2022)

Fats and Fixed Oils 〈401〉, Fatty Acid Composition: 40.0%–60.0% of stearic acid, and the sum of palmitic and stearic acids is NLT 90.0%. • Articles of Botanical Origin 〈561〉, Total Ash

Sample: 1.0 g

Acceptance criteria: NMT 0.1%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers. No storage requirements are specified.

Labeling: Label it to indicate that it is intended for topical and vaginal use only.