Monomeric C18 chromatographic method for the liquid chromatographic determination of lipophilic antioxidants in plants

Reversed-phase liquid chromatography was used to determine lipophilic antioxidants in plants using two monomeric C18 columns operated at 30 °C and 4 °C, with a column-switching technique and acetonitrile-methanol gradient elution. The chromatograms were extracted at different wavelengths using a UV diode array detector (DAD). A wide range of plant antioxidants, including nine carotenoids (neoxanthin, violaxanthin, lutein, zeaxanthin, β-cryptoxanthin, lycopene, canthaxanthin, α-carotene and β-carotene) together with all-trans-retinol, capsaicin, dihydrocapsaicin, chlorophyll a, and chlorophyll b can be separated within 50 min. Fluorometric detection was applied to quantify trace amounts of six vitamin E analogues (α-, δ- and γ-tocopherols and tocotrienols). The detection limits were 0.2–0.4 μg/g for various xanthophylls and 0.04–0.10 μg/g for vitamin E analogues.