Glyceryl Dibehenate
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
1 DEFINITION
Glyceryl Dibehenate is a mixture of diglycerides, mainly glyceryl dibehenate, together with variable quantities of monoglycerides and triglycerides. It contains NLT 15.0% and NMT 23.0% of monoglycerides, NLT 40.0% and NMT 60.0% of diglycerides, and NLT 21.0% and NMT 35.0% of triglycerides. It is obtained by esterification of Glycerin with behenic (docosanoic) acid. The fatty acid may be of vegetable or synthetic origin.
2 IDENTIFICATION
A. It meets the requirements for the content of diglycerides in the Assay.
B. It meets the requirements for Fats and Fixed Oils 〈401〉, Fatty Acid Composition in Specific Tests.
C. MELTING RANGE OR TEMPERATURE, Class II 〈741〉: 65°–77°
3 ASSAY
3.1 PROCEDURE
Mobile phase: Tetrahydrofuran
System suitability solution: 40.0 mg/mL of USP Gly ceryl Dibehenate RS in tetrahydrofuran. Heat gently at about 35°.
Sample solution: 40.0 mg/mL of Glyceryl Dibehenate in tetrahydrofuran. Heat gently at about 35°. Determine the total mass of solvent and substance.
3.1.1 Chromatographic system
(See Chromatography 〈621〉, System Suitability.) Mode: LC
Detector: Refractive index
Column: 7.5-mm × 60-cm; 5-µm 100-Å packing L21
[NOTE—Two 7.5-mm × 30-cm L21 columns may be used in place of one 60-cm column, provided system suitability requirements are met.]
Temperatures
Detector: 35°
Column: 35°
Flow rate: 1.0 mL/min Injection volume: 40 µL
[NOTE—Maintain the temperature of the sample at 35° to avoid precipitation.]
3.1.2 System suitability
Samples: System suitability solution and Sample solution
Suitability requirements: The retention times of the major peaks of the Sample solution correspond to those of the System suitability solution.
[NOTE—The relative retention times for triglycerides, diglycerides, monoglycerides, and glycerin are about 0.73, 0.76, 0.82, and 1.0, respectively.]
3.1.3 Analysis
Sample: Sample solution
Calculate the percentage of monoglycerides in the portion of Glyceryl Dibehenate taken:
Result = [(rU1/rS) × (100 − A − B)] − D
rU1 = peak area of monoglycerides
rS = sum of the peak areas of monoglycerides, diglycerides, and triglycerides
A = content of free glycerin from Limit of Free Glycerin (%)
B = content of water from the Water Determination test in Specific Tests (%)
D = content of free fatty acids (%) using the following formula:
D = AV × [Mr1/(Mr2 × 1000)] × 100
AV = acid value, determined in the Acid Value test in Specific Tests
Mr1 = molecular weight of behenic acid, 340.58
Mr2 = molecular weight of potassium hydroxide, 56.11
1000 = conversion of mg to g
Calculate the percentage of diglycerides in the portion of Glyceryl Dibehenate taken:
Result = (rU2/rS) × (100 − A − B)
rU2 = peak area of diglycerides
rS = sum of the peak areas of monoglycerides, diglycerides, and triglycerides
A = content of free glycerin from Limit of Free Glycerin (%)
B = content of water from the Water Determination test in Specific Tests (%) Calculate the percentage of triglycerides in the portion of Glyceryl Dibehenate taken:
Result = (rU3/rS) × (100 − A − B)
= peak area of triglycerides
rS = sum of the peak areas of monoglycerides, diglycerides, and triglycerides
A = content of free glycerin from Limit of Free Glycerin (%)
B = content of water from the Water Determination test in Specific Tests (%) Acceptance criteria
Monoglycerides: 15.0%–23.0%
Diglycerides: 40.0%–60.0%
Triglycerides: 21.0%–35.0%
4 IMPURITIES
4.1 RESIDUE ON IGNITION 〈281〉
NMT 0.1%
4.2 LIMIT OF FREE GLYCERIN
Mobile phase, System suitability solution, and Chromatographic system: Proceed as directed in the Assay. Standard stock solution: 4.0 mg/mL of USP Gly cerin RS in tetrahydrofuran
Standard solutions: To four 15-mL flasks transfer 0.25, 0.5, 1.0, and 2.0 mL of the Standard stock solution, respectively, and add 5.0 mL of tetrahydrofuran. Determine the concentration for each (mg/g).
Sample solution: Transfer 0.2 g of Glyceryl Dibehenate to a 15-mL flask, and add 5.0 mL of tetrahydrofuran. Heat gently at about 35°. Determine the total mass of solvent and substance.
4.2.1 System suitability
Samples: System suitability solution and Sample solution
Suitability requirements: The retention times of the major peaks of the Sample solution correspond to those of the System suitability solution.
[NOTE—The relative retention times for triglycerides, diglycerides, monoglycerides, and glycerin are about 0.73, 0.76, 0.82, and 1.0, respectively.]
4.2.2 Analysis
Samples: Standard solutions and Sample solution
Using the chromatograms from the Standard solutions, measure the responses for the glycerin peaks. Plot the concentration, in mg/g, of USP Glycerin RS in the Standard solutions versus the glycerin peak responses obtained. From the standard curve so obtained, determine the glycerin concentration, C, in mg/g, in the Sample solution.
Calculate the percentage of free glycerin in the portion of Glyceryl Dibehenate taken:
Result = (C/CU) × 100
C = concentration of glycerin determined from the calibration curve in the Sample solution (mg/g)
CU = concentration of Glyceryl Dibehenate in the Sample solution (mg/g)
Acceptance criteria: NMT 1.0% SPECIFIC TESTS
4.3 FATS AND FIXED OILS, Acid Value, Method I 〈401〉
Sample: 1 g
Analysis: Suspend the Sample in 50 mL of a mixture of alcohol and toluene (1:1) with gentle heating. Continue as directed in Fats and Fixed Oils 〈401〉, Acid Value, beginning with “Add 1 mL of phenolphthalein TS”.
Acceptance criteria: NMT 4
4.4 FATS AND FIXED OILS, Fatty Acid Composition 〈401〉
Glyceryl Dibehenate exhibits the composition profile of fatty acids in Table 1, as determined in the chapter.
Table 1
4.5 WATER DETERMINATION, Method Ia 〈921〉
NMT 1.0% on 1.0-g sample. Use pyridine as the solvent.
5 ADDITIONAL REQUIREMENTS
PACKAGING AND STORAGE: Preserve in tight containers at a temperature not higher than 35°.
LABELING: Label to indicate the origin of behenic acid and glycerin.
USP REFERENCE STANDARDS 〈11〉
USP Glycerin RS
USP Glyceryl Dibehenate RS
