Simultaneous analysis of eight vitamin E isomers in Moringa oleifera Lam. leaves by ultra performance convergence chromatography.

A new method for simultaneous determination of eight vitamin E isomers including α-, β-, γ-, and δ-tocopherol and α-, β-, γ-, and δ-tocotrienol by ultra-performance convergence chromatography (UPC(2)) equipped with a diode array detector was reported. They were separated on a BEH 2-EP column (3.0 mm × 100 mm, 1.7 μm) using gradient elution (95:5-80:20) with a mobile phase consisted of CO2 and methanol:isopropanol (1:1, v/v), back pressure of 1800 psi, flow rate of 1.5 ml/min and detection at 294 nm. The results showed good linearity (R(2)=0.9990-0.9998) and high resolution (1.48-7.67). Limits of detection (LOD) and quantification (LOQ) ranged from 23-49 ng/L and 70-150 ng/L, respectively. Relative standard deviations (RSD) for repeatability and reproducibility were 0.62-3.16% and 0.82-3.34%, respectively. Moreover, this method was successfully applied to analysis the vitamin E isomers in Moringa oleifera leaf samples.