| Abstract
| - Saturated linear fatty acids, derivatized with a near-infrared absorbing fluorescent dye, were separated in100% methanol with 12.5 mM tetraethylammoniumchloride added as a charge carrier. Separation at 380V/cm was acceptable for acids that differed in length by asingle carbon. The labeled linear fatty acids behaved asrandom coils in the nonaqueous separation medium, asshown in a fit to a simple theoretical expression. However,even in 100% methanol with a trimethylsilylated capillary,significant adsorption to the capillary wall occurred, whichreduced resolution and slowed the separation. Additionof water to the methanol medium caused significantdifferences in separation behavior of high molecularweight acids (>C16). Addition of a cetyltrimethylammonium bromide surfactant to the separation medium dynamically coated the capillary and greatly improved theseparation. The surfactant also interacted with the acyltail, apparently causing it to collapse. Resolution in anoptimal separation medium (20 mM surfactant) rangedfrom 1.6 to 1.1, depending on chain length, and theoretical plate heights were under 4 μm (N> 105). Resolutionwas more than adequate to separate stearic (C18:0) fromoleic (C18:1) acid, as well as other unsaturated C18homologues.
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