Shape selectivity of C30 phases for RP-HPLC separation of tocopherol isomers and correlation with MAS NMR data from suspended stationary phases

Vitamin E (tocopherol) acts in various organisms as the main free radical scavenger, This capacity, which is enhanced by the synergetic effect of vitamin C and carotenes, points to a possible application as anti-tumor agent in chemotherapy. There are several isomeric forms, namely alpha-, beta-, gamma-, and delta-tocopherol, having different antioxidative abilities, with alpha-tocopherol being the most biologically active, Using methanol as eluent and a C-30 stationary phase, we achieved complete separation of alpha-, beta-, gamma-, and delta-tocopherol and alpha-tocopherol acetate by RP-HPLC within 14 min, Detection was performed by UV and H-1 NMR spectroscopy, The advantage of NMR is the possibility of structural identification of chromatographic peaks. Also, coeluting peaks are easily recognized, The enhanced shape recognition of the C-30 phase has been attributed to the high order of the alkyl chains of the stationary phase, This has, so far, been proven by solid-state NMR spectroscopy, We now introduce the technique of C-13 MAS NMR spectroscopy of suspended stationary phases. The resulting NMR spectra reveal that, in the presence of weak eluents, like methanol, the overall high order of the C-30 chains is slightly altered, whereas in stronger elements, like MTBE, the alkyl chains possess a higher mobility.