Journal of Lipid Research, Vol. 13, 745-749, November 1972
Copyright © 1972 by Lipid Research, Inc.

Artifacts in ultracentrifugal estimation of aqueous fatty acid concentration

K. Y. Lee

Department of Physiology, The University of Western Australia, Nedlands, Western Australia, 6009

Ultracentrifugation for determination of isotropic concentrations of fatty acids is widely used. However, several artifacts, which would affect the isotropic concentration, could occur if care is not taken. These include sedimentation of micelles, incomplete flotation of unsolubilized oil, and uptake of labeled fatty acid by the walls of centrifuge tubes. The first artifact can be overcome by sampling large volumes from the ultracentrifuged sample, and the second by ultracentrifugation for long periods; a force-duration of 7.2 X 10⁷ g-min is suitable. The third artifact cannot be eliminated but may be made constant if the duration of exposure of lipid mixtures to centrifuge tubes is kept constant.

Supplementary key words oleic acid • taurocholate • flotation • micellar sedimentation • partition

Submitted on February 29, 1972
Accepted on July 5, 1972

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