Determination of estolide molecular weight distribution via gel permeation chromatography

Authors: Bantchev, Grigor; Cermak, Steven - Steve; Durham, Amber; Price, Neil

Submitted to: Annual Meeting and Expo of the American Oil Chemists' Society
Publication Type: Abstract Only
Publication Acceptance Date: 5/3/2021
Publication Date: 5/3/2021
Citation: Bantchev, G.B., Cermak, S.C., Durham, A.L., Price, N.P. 2021. Determination of estolide molecular weight distribution via gel permeation chromatography. In: Proceedings of the American Oil Chemists' Society Annual Meeting & Expo, May 3-14, 2021, Virtual Meeting.

Interpretive Summary:

Technical Abstract: Using the universal calibration and the Mark-Houwink equation (MHE) ([']_j=K(M_j)^a ), three batches of oleic estolide acids and their corresponding 2-ethylhexyl esters were characterized using gel permeation chromatography (GPC). The MHE parameters in tetrahydrofuran (THF) at 40 °C were determined (for acids: a = 0.442±0.003 and logK=2.505±0.007, for esters: a =0.531±0.006 and logK =2.79±0.02). The fits of the GPC chromatograms also yielded the oligomeric composition of the estolides, which can be used to calculate the estolide number (EN) of an estolide mixture, and other molecular-weight distribution parameters, such as number-average molecular weight (Mn), weight-average molecular weight (Mw), and dispersity (Ð). Using the Deming line fit, we concluded the GPC should be approximately three times more sensitive than currently used methods for determination of EN values.