RAPID QUANTIFICATION OF ALPHA-TOCOPHEROL IN PLASMA AND LOW-DENSITY AND HIGH-DENSITY LIPOPROTEINS

We have developed two methods for measuring the alpha-tocopherol conte nt in plasma and lipoproteins (LDL and HDL). In procedure 1, plasma or lipoproteins are deproteinized with ethanol containing delta-tocopher ol as internal standard and then extracted with hexane or ethyl acetat e. The organic layer is removed and evaporated, and the residue is red issolved in methanol and injected into a reversed-phase HPLC. In proce dure 2, plasma or lipoproteins are diluted in a methanol and ethanol m ixture containing the same internal standard. The solution is vortex-m ixed, centrifuged, and directly injected into the column, The tocopher ols are eluted with an isocratic methanol mobile phase at a flow rate of 1 mL/min and detected by fluorescence (lambda(exc) = 295 nm, lambda (em) = 330 nm). Recoveries are similar to 100% in both cases. Between- run CVs were 8.39% for procedure 1 and 6.55% for procedure 2. Small sa mple requirement, simplicity of sample preparation, short assay time, and good reproducibility make procedure 2 ideal for clinical or resear ch use. This method was applied to determination of alpha-tocopherol i n plasma of patients whose diet was supplemented with alpha-tocopherol and in LDL and HDL.