Development and Evaluation of a New Method for the Determination of the Carotenoid Content in Selected Vegetables by HPLC and HPLC-MS-MS

摘要

Epidemologic studies have shown inverse correlation between the consumption of carotenoid-rich regetables and the incidence of cancer. Therefore, analytical techniques for the quantitative determination of carotenoids in complex sample matrices are important. The most used method is reversed-phase (RP)-high-performance liquid chromatography (HPLC). In this study, seventeen mobile-phase systems described in the literature and six RP-HPLC columns with differences in particle size and porosity are evaluated. Derived from these results, a new mobile-phase (acetonitrile, methanol, chloroform, and n-heptane) including solvent modifiers is presented, which allows an improved and more efficient separation of carotenoids. Form all columns tested, the best chromatographic parameters are found using a silica C_(18) column (250 X 2 mm, 5 #mu#m, 100 A). As was found, absorbance detection at 450 nm allows the determination of the carotenoids down to the picogram range with good linearity (R~2>0.98). For the identification and quantitation of carotenoids in complex sample matrices (containing) additionally other ultraviolet-absorbing compounds), the optimized RP chromatographic system is coupled to a mass spectrometer (MS) using an atmospheric pressure ionization interface. The calibration plots show hgih linearity (R~2>0.99), and the detection limit is found in the lower nanogram range. Furthermore, collision-induced dissociation in the ion source allows for the identification of carotenoids by their characteristic fragmentation pathways. In this study, a total of nine species of vegetables commonly consumed in Central Europe are analyzed for their contents of carotenoids (namely lutein, zeaxanthin, #beta#-cryptoxanthin, and #beta#-carotene) by RP-HPLC and RP-HPLC-MS-MS. It is found that good sources for lutein are spinach, kale, and broccoli, and sources for #beta#-carotene are broccoli, spinach, kale, carrots, and tomatoes. This new method is an improvement for the identification and quantitation of carotenoids in complex biological tissues.