Propylene Glycol Dicaprylate/Dicaprate
(proe' pi leen glye' kol dye kap' ri late/dye kap' roe ate).

Decanoic acid, mixed diesters with octanoic acid and propylene glycol     [68583-51-7].
Propylene Glycol Dicaprylate/Dicaprate is a mixture of the propylene glycol mono- and diesters of caprylic acid (C8H16O2) and capric acid (C10H20O2), the diesters fraction being predominant.
•  B. Thin-Layer Chromatography Identification Test 201
Standard solution:  50 mg/mL of USP Propylene Glycol Dicaprylate/Dicaprate RS in methylene chloride
Sample solution:  50 mg/mL of Propylene Glycol Dicaprylate/Dicaprate in methylene chloride
Application volume:  10 µL, as streaks
Developing solvent system:  Ether and hexane (7:3)
Spray reagent:  0.1 mg/mL of rhodamine 6G in alcohol
Samples:  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 from the Sample solution correspond to those from the Standard solution.
•  C. It meets the requirements of the test for Fats and Fixed Oils 401, Fatty Acid Composition.
Inorganic Impurities 
•  Alkaline Impurities
Sample:  2.0 g of Propylene Glycol Dicaprylate/Dicaprate
Analysis:  Dissolve the Sample in a mixture of 1.5 mL of alcohol and 3.0 mL of ether. Add 0.05 mL of bromophenol blue TS.
Acceptance criteria:  NMT 0.15 mL of 0.01 N hydrochloric acid is required in order to change the color of the indicator to yellow.
•  Fats and Fixed Oils, Fatty Acid Composition 401: Propylene Glycol Dicaprylate/Dicaprate exhibits the composition profile of fatty acids shown in the following table:
Carbon-Chain Length Number of
Double Bonds
6 0 2.0
8 0 50.0–80.0
10 0 20.0–50.0
12 0 3.0
14 0 1.0
•  Fats and Fixed Oils, Unsaponifiable Matter 401: NMT 0.5%, determined on 5.0 g
•  Water Determination, Method Ia 921: NMT 0.1%, 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 specified.
•  USP Reference Standards 11
USP Propylene Glycol Dicaprylate/Dicaprate RS
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Topic/Question Contact Expert Committee
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. 36(5) Page 1236