HPLC-HG-AFS Determination of 5 Species of Selenium in Foodstuffs Rich in Selenium

It was proposed to apply HPLC-HG-AFS to speciation analysis of selenium in foodstuffs rich in selenium. Papain (PP) was selected as extractant to separate 5 species of selenium from the sample under the following optimized conditions:① ratio of sample to solution was 1 g/40 mL; ② amount of 50.0 g·L^-1 PP solution added was 20 mL; ③ extracted in a water bath at 60℃ for 8 h. The extract was cooled, centrifuged, and the supernatant was taken for HPLC separation, using Hamilton PRP-X100 chromatographic column of ion exchange as stationary phase, and 35 mmol·L^-1 (NH₄)₂HPO₄ solution (pH 6.0) as mobile phase. The 5 species of seleniumSe(Ⅵ), Se(Ⅳ), SeCys₂, MeSeCys and SeMet were separated clearly within 16 min. The solutions containing separately the 5 species of selenium were then used for determination of selenium by HG-AFS. As shown by the results, linear relationships were obtained between values of peak area and mass concentrations of the 5 species of selenium in the same range of 5 to 100 μg·L^-1. Values of detection limits (3S/N) for the 5 species of selenium were between 0.39 to 1.18 μg·L^-1. Tests for recovery and precision were made by addition of standard solutions to the sample of rice rich in selenium, giving values of recovery ranged from 80.2% to 118%, and RSD's (n=6) ranged from 2.1% to 8.2%.