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Propylene Glycol Monolaurate

Dodecanoic acid, monoester with 1,2-propanediol.
Lauric acid, monoester with propane-1,2-diol.
» Propylene Glycol Monolaurate is a mixture of the propylene glycol mono- and di-esters of lauric acid. The requirements for monoester and diester content differ for the two types of Propylene Glycol Monolaurate, as set forth in the accompanying table.
Content of
monoesters (%)
Content of
diesters (%)
Min. Max. Min. Max.
Type I 45.0 70.0 30.0 55.0
Type II 90.0 10.0
Packaging and storage— Preserve in well-closed containers, and protect from moisture. No storage requirements specified.
Labeling— Label it to indicate the type (Type I or Type II).
USP Reference standards 11 USP Propylene Glycol RS. USP Propylene Glycol Monolaurate RS.
A: Thin-Layer Chromatographic Identification Test 201
Test solution: 50 mg per mL, in methylene chloride.
Developing solvent solution: a mixture of hexane and ether (30:70)
Spray reagent— Prepare a 0.1 mg per mL solution of rhodamine 6G in alcohol.
Procedure— 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: the RF values of the principal spots obtained from the Test solution correspond to those obtained from the Standard solution.
B: It complies with the requirements of the test for Fatty acid composition.
Acid value 401: not more than 4.
Iodine value 401: not more than 1.
Saponification value 401: between 210 to 245 for propylene glycol monolaurate (Type I) and between 200 to 230 for propylene glycol monolaurate (Type II).
Fatty acid composition 401 Propylene Glycol Monolaurate exhibits the following composition profile of fatty acids, determined as directed in the chapter.
Fatty Acids Carbon-chain
Caprylic acid C8 not more than 0.5
Capric acid C10 not more than 2.0
Lauric acid C12 not less than 95.0
Myristic acid C14 not more than 3.0
Palmitic acid C16 not more than 1.0
Water, Method Ia 921: not more than 1.0%, using a mixture of methanol and methylene chloride (1:1) in place of methanol in the titration vessel.
Total ash 561: not more than 0.1%.
Limit of propylene glycol—
Mobile phase— Proceed as directed in the Assay.
Propylene glycol standard stock solution— Prepare a solution containing a known concentration of about 4 mg per mL of USP Propylene Glycol RS in tetrahydrofuran.
Propylene glycol standard solutions— Into four 15-mL flasks, introduce respectively, 0.25 mL, 0.5 mL, 1.0 mL, and 2.5 mL of Propylene glycol standard stock solution, and dilute with tetrahydrofuran to 5.0 mL. In a fifth 15-mL flask, introduce 5.0 mL of Propylene glycol standard stock solution.
Test solution— Use the Assay preparation.
Chromatographic system— Proceed as directed in the Assay.
Procedure— Separately inject equal volumes (about 40 µL) of the Propylene glycol standard solutions and the Test solution into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Prepare a standard curve of peak area versus concentration, in mg per mL, of propylene glycol in the Propylene glycol standard solutions. Obtain the concentration, C, in mg per mL, of propylene glycol in the Test solution from the standard curve. Calculate the percentage of free propylene glycol in the portion of Propylene Glycol Monolaurate taken by the formula:
in which V is the final volume of the Test solution; and W is the weight, in mg, of Propylene Glycol Monolaurate used to prepare the Test solution: not more than 5.0% is found for propylene glycol monolaurate (Type I); and not more than 1.0% is found for propylene glycol monolaurate (Type II).
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Mobile phase: tetrahydrofuran.
Assay preparation— Accurately weigh about 200 mg of Propylene Glycol Monolaurate into a 15-mL flask, add 5 mL of tetrahydrofuran, and shake to dissolve.
Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a refractive index detector and a 7-mm × 60-cm column that contains 5-µm packing L21 (100Å). The flow rate is about 1 mL per minute. The column and detector temperatures are maintained at 40. [NOTE—Two 7-mm × 30-cm L21 columns may be used in place of one 60-cm column provided system suitability requirements are met.] Chromatograph the Assay preparation, and record the peak responses as directed for Procedure. The order of elution is diesters, monoesters, and propylene glycol. The relative standard deviation for replicate injections determined from the monoester peak is not more than 1.0%.
Procedure— Inject a volume (about 40 µL) of the Assay preparation into the chromatograph, record the chromatogram, and measure the responses for the major peaks. Calculate the percentage of monoesters or diesters in the portion of Propylene Glycol Monolaurate taken by the formula:
(100 D)(rU / rs)
in which D is the sum of the percentage content of propylene glycol and percentage content of free fatty acids; rU is the peak response for monoesters or diesters; and rs is the sum of the responses of the monoesters and diesters peaks. Calculate the percentage content of free fatty acids using the formula:
in which A is the acid value.NF24
Auxiliary Information— Staff Liaison : Catherine Sheehan, B.Sc., Scientist
Expert Committee : (EM105) Excipient Monographs 1
USP29–NF24 Page 3412
Pharmacopeial Forum : Volume No. 31(2) Page 501
Phone Number : 1-301-816-8262