Determination of tocopherols by packed column supercritical fluid chromatography [SFC]
Supercritical fluid chromatographic (SFC) separations of a-tocopheryl acetate, α-, ß-, y- and -tocopherol have been achieved on a Spherisorb S3 ODS2 column in about 15 minutes. Separation efficiency of this method has been optimised with respect to the effect of pressure, percent of methanol in the mobile phase, temperature and flow rate, resulting in theoretical plate numbers (N) varying from 63000 to 90000 per metre. Linear correlations have been found between log k' (retention factor) and fluid density for all of the tested compounds, and a van't Hoff plot yielded linear correlation between log k' and T-1 at constant mobile phase density. Linearity and repeatability were found to be acceptable with detection limits from approximately 20 ng for α-, ß-, y- and ő-tocopherol to 10 ng for a-tocopheryl acetate at a signal to noise ratio = 3. Results obtained by use of the developed SFC method to determination of tocopherols in plant oils obtained by SFE (supercritical fluid extraction) and by aqueous enzymatic processing are presented.