| Abstract
| - An on-line method to detect and quantify antioxidant species in complex extracts has been developedas a combination of conventional HPLC separation and a postcolumn reaction with phosphomolybdenum reagent at acidic pH. Sample analytes were chromatographed by HPLC, and the postcolumnformation of a phosphate/Mo(V) complex was detected at 598 nm with an on-line absorbance detector.An optimized instrumental system was set up using pure α-tocopherol, and it was successfully testedwith complex food extracts including lettuce, tomato, red pepper, and soybean seed, where severaltocopherols and carotenoids were identified. A potential application of this detection method toquantitatively determine different antioxidants was considered, and a specific application to thedetermination of tocopherols was developed. The new method was characterized with respect tolinearity interval, repeatability, and reproducibility, the quantitative results obtained were validated bycomparison with a conventional HPLC method with fluorometric detection, and it was applied to thedetermination of tocopherols in different foods. The results suggest that the proposed on-line HPLCmethod can be a powerful instrument for the detection, purification, and characterization of naturalantioxidants. Keywords: Antioxidants; tocopherols; on-line detection; HPLC (high-performance liquid chrmatography); molybdenum; phosphate
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