UPLC method for the determination of vitamin E homologues and derivatives in vegetable oils, margarines and supplement capsules using pentafluorophenyl column

Abstract

A sensitive and rapid reversed-phase ultra performance liquid chromatographic (UPLC) method for the simultaneous determination of tocopherols (α‐, β‐, γ‐, δ‐), tocotrienols (α‐, β‐, γ‐, δ‐), α‐tocopherol acetate and α‐tocopherol nicotinate is described. The separation was achieved using a Kinetex pentafluorophenyl (PFP) column (150×2.1mm, 2.6µm) with both photodiode array (PDA) and fluorescence (FL) detectors that were connected in series. Column was thermostated at 42°C. Under a gradient system consisting of methanol and water at a constant flow rate of 0.38mLmin−1, all the ten analytes were well separated in less than 9.5min. The method was validated in terms of linearity, limits of detection and quantitation, precision and recoveries. Calibration curves of the ten compounds were well correlated (r2>0.999) within the range of 100 to 25,000μgL−1 for α‐tocopherol acetate and α‐tocopherol nicotinate, 10 to 25,000μgL−1 for α‐tocotrienol and 5 to 25,000μgL−1 for the other components. The method is simple and sensitive with detection limits (S/N, 3) of 1.0 to 3.0μgL−1 (FL detection) and 30 to 74μgL−1 (PDA detection). Relative standard deviations for intra- and inter-day retention times (<1%) and peak areas (≤4%) were obtained. The method was successfully applied to the determination of vitamin E in vegetable oils (extra virgin olive, virgin olive, pomace olive, blended virgin and refined olive, sunflower, soybean, palm olein, carotino, crude palm, walnut, rice bran and grape seed), margarines and supplements.