An improved fluorimetric HPLC method for quantifying tocopherols in Brassica rapa L. subsp. sylvestris after harvest

This study describes a reliable method suitable for the quantitative determination of tocopherols with a fast, easy extraction procedure and a rapid, sensitive HPLC fluorescence detection, that results in a better signal-to-noise ratio and lowers the detection limit. The limit of detection of this assay is about 0.06 mg L−1 and the linearity is in a range of 0.06–2 mg L−1. The method has been tested on samples of Brassica rapa L. subsp. sylvestris after harvest as affected by various storage temperatures (4 °C, 9 °C and 20 °C). The fluorescent detection makes it possible to measure tocopherols in these plants even when their concentration is extremely low, as at harvest, without the interference of other metabolites. The increase of tocopherols was followed for 14 days after harvest, and in particular the metabolic profile of α-tocopherol was compared with that of ascorbate, dehydroascorbate and chlorophyll.