title: Artifacts in ultracentrifugal estimation of aqueous fatty acid concentration.
abstract: 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 10(7) 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.
mesh_terms: D002247:Carbon Isotopes; D002855:Chromatography, Thin Layer; D003102:Colloids; D005188:False Negative Reactions; D005189:False Positive Reactions; D005227:Fatty Acids / Q000032:analysis*; D046911:Macromolecular Substances; D008722:Methods; D009829:Oleic Acids / Q000032:analysis; D009994:Osmolar Concentration; D013656:Taurocholic Acid / Q000032:analysis; D014461:Ultracentrifugation
chemical_list: D002247:Carbon Isotopes; D003102:Colloids; D005227:Fatty Acids; D046911:Macromolecular Substances; D009829:Oleic Acids; D013656:Taurocholic Acid