Abstract: Selenium contents with different chemical states and valences in two kinds of Se-enriched s.pirulina tablets were determined by atomic fluorescence spectrometry generated from hydride. The effects of atomizer height, HCl concentration and KBH4 concentration on Se fluorescence signal were investigated. The microwave digestion and wet digestion were also compared. In addition, the effects of ultrasonic cell-break method and repeated freezing-thaw method on the extraction rate of protein were explored. Results indicated that two digestion methods had no significant difference (P = 0.6900), and selenium content in samples treated by repeated freezing-thaw method was only 25%－30% of that treated by ultrasonic cell-break method, which suggested that ultrasonic cell-break method was better than repeated freezing-thaw method. Under the optimal conditions, selenium contents in Se-enriched s.pirulina tablets were significant difference (P < 0.0001). Although both inorganic Se and organic Se co-existed, the organic Se in the states of Se (IV) and Se (VI) was still prominent, which was up to 60%. The contents of Se in both states in sample 1 revealed a significant difference (P = 0.0094), but the contents of Se in both states in sample 2 had no significant difference (P = 0.2269). The detection limit of this method was 0.64 ng/g, and the recovery rate of spiked samples was in the range of 93.0%－98.8%. Therefore, this method is characteristics of simple operation, high sensitivity and low detection limit, and provides a theoretical reference for determining the content of Se in different states and valences from Se-enriched s.pirulina tablets.

Key words: atomic fluorescence spectrometry, Se-enriched s.pirulina tablets, Se, chemical state, valence