Sl. Abidi et Tl. Mounts, SEPARATIONS OF TOCOPHEROLS AND METHYLATED TOCOLS ON CYCLODEXTRIN-BONDED SILICA, Journal of chromatography, 670(1-2), 1994, pp. 67-75
alpha-, beta-, gamma-, and delta-tocopherols (methyl-substituted tocol
s) and 5,7-dimethyltocol were separated by normal-phase HPLC on beta-
or gamma-cyclodextrin-bonded silica (CDS) with fluorescence detection.
The HPLC behavior of the tocol components was studied under various m
obile phase conditions. Hexane or cyclohexane was used in combination
with oxygen-containing solvents (alcohol, ether, and esters) in binary
and ternary mobile phases. Capacity factors (k') and separation facto
rs (alpha) for adjacent tocol components were determined. Incorporatio
n of non-polar ethers in the hydrocarbon (hexane or cyclohexane) mobil
e phases favored the separation of beta- and gamma-tocopherols with im
proved alpha values, which enabled trace analysis of the beta-isomer p
resent in soybean oil. Analyte solutes tended to be more strongly adso
rbed in mobile phases containing branched-chain alcohols and ethers th
an in those containing the corresponding straight-chain solvents. Gene
rally, the k' values obtained with hexane mobile phases or with the be
ta-CDS phase were greater than those observed in HPLC with cyclohexane
mobile phases or with the gamma-CDS phase.