Propylene Glycol Dilaurate
(proe' pi leen glye' kol).
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Lauric acid, diester with propane-1,2-diol;    
Propane-1,2-diyl didodecanoate     440.70 [22788-19-8].
Propylene Glycol Dilaurate is a mixture of the propylene glycol mono- and diesters of lauric acid. It contains NLT 70.0% of diesters and NMT 30.0% of monoesters.
•  A. Thin-Layer Chromatographic Identification Test 201
Standard solution:  50 mg/mL of USP Propylene Glycol Dilaurate RS in methylene chloride
Sample solution:  50 mg/mL of Propylene Glycol Dilaurate in methylene chloride
Developing solvent system:  Hexane and ether (3:7)
Spray reagent:  0.1 mg/mL of rhodamine 6G in alcohol
Analysis:  Apply 200 µg of the Standard solution and Sample solution. Develop the chromatogram over a path of 15 cm, and dry the plate in a current of air. Spray the plate with Spray reagent, and locate the spots on the plate by examination under UV light at a wavelength of 365 nm.
Acceptance criteria:  The RF values of the principal spots of the Sample solution correspond to those of the Standard solution.
•  B. Fats and Fixed Oils, Fatty Acid Composition 401: Meets the requirements
•  Procedure
Mobile phase:  Tetrahydrofuran
Sample solution:  200 mg of Propylene Glycol Dilaurate in 5 mL of tetrahydrofuran
Chromatographic system 
Mode:  LC
Detector:  Refractive index
Column:  7-mm × 60-cm; 5-µm packing L21 (100)
[Note—Two 7-mm × 30-cm L21 columns may be used in place of one 60-cm column, provided system suitability requirements are met. ]
Column:  40
Detector:  40
Flow rate:  1 mL/min
Injection size:  40 µL
System suitability 
Sample:  Sample solution
[Note—Elution order: diesters, monoesters, propylene glycol. ]
Suitability requirements 
Relative standard deviation:  NMT 1.0% is determined from the monoester peak.
Sample:  Sample solution
Calculate the percentage of monoesters or diesters in the portion of Propylene Glycol Dilaurate taken:
Result = (rU/rT) × (100 D)
rU== peak response for monoesters or diesters
rT== sum of the responses of the monoester and diester peaks
D== sum of the percentage content of propylene glycol and the percentage content of free fatty acids
Calculate the percentage content of free fatty acids:
Result = (A/561.1) × 200
A== acid value
Acceptance criteria:  NLT 70.0% of diesters and NMT 30.0% of monoesters
Inorganic Impurities 
Organic Impurities 
•  Procedure: Limit of Propylene Glycol
Mobile phase:  Proceed as directed in the Assay.
Standard stock solution:  4 mg/mL of USP Propylene Glycol RS in tetrahydrofuran
Standard solutions:  Into four 15-mL flasks, introduce respectively 0.25, 0.5, 1.0, and 2.5 mL of Standard stock solution, and dilute with tetrahydrofuran to 5.0 mL. In a fifth 15-mL flask, introduce 5.0 mL of Standard stock solution.
Sample solution:  Use the Sample solution from the Assay.
Chromatographic system:  Proceed as directed in the Assay.
Samples:  Standard solutions and Sample solution
Prepare a standard curve of peak area versus concentration, in mg/mL, of propylene glycol in the Standard solutions. Obtain the concentration, C, in mg/mL, of propylene glycol in the Sample solution from the standard curve.
Acceptance criteria:  NMT 2.0% of propylene glycol is found.
•  Fats and Fixed Oils, Fatty Acid Composition 401: Propylene Glycol Dilaurate exhibits the following composition profile of fatty acids, determined as directed in the chapter.
Fatty Acids Carbon-Chain Length Percentage
Caprylic acid C8 NMT 0.5
Capric acid C10 NMT 2.0
Lauric acid C12 NLT 95.0
Myristic acid C14 NMT 3.0
Palmitic acid C16 NMT 1.0
•  Water Determination, Method Ia 921: NMT 1.0%, using a mixture of methanol and methylene chloride (1:1) in place of methanol in the titration vessel
•  Packaging and Storage: Preserve in well-closed containers, and protect from moisture. No storage requirements are specified.
•  USP Reference Standards 11
USP Propylene Glycol RS Click to View Structure
USP Propylene Glycol Dilaurate RS
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Monograph Robert H. Lafaver, M.S.
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(EXC2010) Monographs - Excipients
Reference Standards RS Technical Services
USP35–NF30 Page 1933
Pharmacopeial Forum: Volume No. 35(3) Page 599