Polyglyceryl Dioleate

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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R–O–(CH₂ –CH(OR)–CH₂ –O) –R R = H, or CO–C₁₇H₃₃

1,2,3-Propanetriol, homotrimer, di[(9Z)-9-octadecenoate];

Triglyceril dioleate;

Polyglyceryl 3 dioleate CAS RN®: 9007-48-1.R–O–(CH₂ –CH(OR)–CH₂ –O) –R R = H, or CO–C₁₇H₃₃

1,2,3-Propanetriol, homohexamer, di[(9Z)-9-octadecenoate];

Hexaglyceril dioleate;

Polyglyceryl 6 dioleate

CAS RN®: 76009-37-5.

1 DEFINITION

Polyglyceryl Dioleate is a mixture of polyglyceryl diesters of mainly oleic acid, obtained by esterification of poly Glycerin and oleic acid. The polyglycerin consists mainly of triglycerin or hexaglycerin.

2 IDENTIFICATION

Change to read:

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197F (CN 1-May-2020)

B. Meets the requirements of the test for Content of Fatty Acids

C. Meets the requirements of the test for Fats and Fixed Oils 〈401〉, Hydroxyl Value. [Note - This test will differentiate for Polyglyceryl 3 Dioleate and Polyglyceryl 6 Dioleate.]

3 ASSAY

Content of Fatty Acids

0.5 N methanolic sodium hydroxide solution: Dissolve 20 g of sodium hydroxide in 50 mL of water, and mix. Cool to room temperature, and add 950 mL of methanol.

Boron trifluoride methanol solution: Dissolve 14 g of boron trifluoride in methanol to make 100 mL, and mix well.1

Saturated sodium chloride solution: Dissolve about 375 g of sodium chloride in water to make 1000 mL.

Standard solution: Prepare the calibration ester mixture by mixing up each individual ester component (see Table 1 for the component’s composition). Dissolve 500 mg of the calibration ester mixture in n-heptane, and dilute with n-heptane to 50 mL. [Note - Commercially available mixtures of fatty acid methyl esters may also be used.]

Table 1

Sample solution: Introduce 100 mg of Polyglyceryl Dioleate into a 25-mL conical flask fitted with a suitable water-cooled reflux condenser and a magnetic stir bar. Add 2 mL of 0.5 N methanolic sodium hydroxide solution, mix, and reflux for about 30 min. Add 2 mL of Boron trifluoride methanol solution through the condenser and re flux for about 30 min. Add 4 mL of n-heptane through the condenser, and reflux for 5 min. Cool, remove the condenser, add about 10 mL of Saturated sodium chloride solution, shake, add a quantity of Saturated sodium chloride solution to bring the upper layer up to the neck of the flask, and allow the layers to separate. Collect 2 mL of the n-heptane layer (upper layer), wash with three quantities, each at 2 mL of water, and dry the n-heptane phase over anhydrous sodium sulfate.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: GC

Detector: Flame ionization

Column: 0.32-mm × 30-m fused-silica capillary; 0.25-μm layer of phase G16

Temperature

Detector: 250°

Injection port: 240°

Column: See temperature program table below.

Carrier gas: Nitrogen

Flow rate: 1.0–1.2 mL/min

Injection size: 1 μL

Injection type: Split injection. The split ratio is about 1:80.

System suitability

Sample: Standard solution

[Note - See the relative retention time table below.]

^a There could be an isomer eluting at a relative retention time of 1.39.

^b There could be two isomers eluting at relative retention times of 1.45 and 1.48.

Suitability requirements

Resolution: NLT 1.5 between the peaks due to methyl stearate and methyl oleate

Relative standard deviation: NMT 6.0% for the palmitate and stearate peak areas

Analysis

Samples: Standard solution and Sample solution

Identify the fatty acid ester peaks of the Sample solution by comparing the retention times of these peaks with those of the Standard solution, and measure the peak areas for all of the fatty acid esters in the Sample solution.

Calculate the percentage of each fatty acid ester component in the test specimen:

Result = (A/B) × 100

A = peak area of each individual fatty acid ester component

B = sum of the peak areas, excluding the solvent peak, of the Sample solution

Acceptance criteria: Polyglyceryl Dioleate exhibits the following composition profile of fatty acids.

^a The content of C18:2 or C18:3 is the content of each fatty acid with its respective isomers.

4 IMPURITIES

Inorganic Impurities

Residue on Ignition

Analysis: Heat a silica crucible to redness for 30 min, allow to cool in a desiccator, and weigh. Evenly distribute about 1.0 g of Polyglyceryl

Dioleate in the crucible, and weigh. Dry at 100°–105° for 1 h, and ignite in a muffle furnace at 600 ± 25°, until the test substance is thoroughly charred. Perform the test for Residue on Ignition 〈281〉 on the residue obtained, starting with “Moisten the sample with a small amount (usually 1 mL) of sulfuric acid.”

Acceptance criteria: NMT 1%

5 SPECIFIC TESTS

Acid Value

Analysis: Accurately weigh (to within 0.1 mg) 5–10 g of Polyglyceryl Dioleate, add 10 mL of alcohol and 3 drops of phenolphthalein TS, and titrate with 0.1 N potassium hydroxide VS or 0.1 N sodium hydroxide VS until the solution remains faintly pink after shaking for 30 s.

Proceed as directed in Fats and Fixed Oils 〈401〉, Acid Value to perform the calculation.

Acceptance criteria

Polyglyceryl 3 dioleate: NMT 6

Polyglyceryl 6 dioleate: NMT 6

Fats and Fixed Oils, Hydroxyl Value 〈401〉

Acceptance criteria

Polyglyceryl 3 dioleate: 195–245, determined on a 0.7-g to 1.0-g specimen

Polyglyceryl 6 dioleate: 270–320, determined on 0.5-g to 0.7-g specimen

Iodine Value

Analysis: Accurately weigh 0.15 g of Polyglyceryl Dioleate, transfer to a dry 250-mL flask with a ground-glass stopper, and add 25 mL of methylene chloride. Add 20 mL of the Wijs’ solution.² Close the flask, and keep it in the dark for 1 h while shaking frequently. Perform the test in Fats and Fixed Oils 〈401〉, Iodine Value, starting with “Then add, in the order named, 30 mL of potassium iodide TS and 100 mL of water.”

Acceptance criteria

Polyglyceryl 3 dioleate: 60–80

Polyglyceryl 6 dioleate: 50–70

Fats and Fixed Oils, Peroxide Value 〈401〉: Use 30 mL of a mixture of glacial acetic acid and methylene chloride (3:2) to replace 30 mL of a mixture of glacial acetic acid and chloroform (3:2).

Acceptance criteria

Polyglyceryl 3 dioleate: NMT 12.5

Polyglyceryl 6 dioleate: NMT 12.5

Fats and Fixed Oils, Saponification Value 〈401〉: Determined on 1-g specimen

Acceptance criteria

Polyglyceryl 3 dioleate: 135–155

Polyglyceryl 6 dioleate: 110–140

Water Determination, Method I 〈921〉 : NMT 1%, determined on a 2.0-g specimen

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight, light-resistant containers, protected from heat and moisture.

Labeling: Label to indicate whether it is Polyglyceryl 3 Dioleate or Polyglyceryl 6 Dioleate.

USP Reference Standards 〈11〉

USP Methyl Linoleate RS

USP Methyl Linolenate RS

USP Methyl Myristate RS

USP Methyl Oleate RS

USP Methyl Palmitate RS

USP Methyl Palmitoleate RS

USP Methyl Stearate RS

USP Polyglyceryl 3 Dioleate RS

USP Polyglyceryl 6 Dioleate RS

¹ Boron trifluoride–methanol solution (14% in methanol) is also commercially available from Sigma, B-1252, or equivalent quality.

² Wijs’ reagent RPE for analysis from Carlo Erba Reference 491902; Wijs’ solution from www.sigmaaldrich.com, or equivalent quality.