Separation and Identification of Tocotrienol Isomers by HPLC−MS and HPLC−NMR Coupling

Abstract

A crude palm-oil extract rich in vitamin E homologues was investigated by HPLC−MS and HPLC−NMR coupling. For mass spectrometry a newly introduced ionization technique called Coordination Ion Spray (CIS) was used. Through the addition of silver ions to the HPLC eluent, the ionization process of nonpolar substances is facilitated. Chromatography and all coupling experiments were conducted on a C₃₀ column which exhibited an extraordinary shape selectivity and overwhelming sample-loading capability. Experiments were performed with pure methanol as an eluent which proved to be ideal for NMR spectroscopy as well as mass spectrometry. All necessary information for unambiguous structural assignment was collected within 45 min of the LC−NMR experiment and 15 min of the LC−MS experiment. Six compounds were identified, i.e., α-, β-, γ-, and δ-tocotrienol, α-tocoenol, and α-tocopherol.