CHAPTER 12: Assay of Selenium in Dietary Supplements

Due to the insufficient amount of selenium in the diet, supplementation is advised. Dietarysupplements may contain inorganic and/or organic selenium forms.This chapter overviews the most relevant analytical approaches for assaying selenium in dietary supplements in terms of sample pretreatment, selenium preconcentration and separation from the matrix components, and instrumental techniques suitable for measuring trace selenium concentration, with special reference to the main limitations that should be overcome to attain accurate results of the determination. Important topics such as selenium losses due to its volatility, limited recovery of different selenium species from the sample, and matrix effects caused by both inorganic and organic matrix components are discussed throughout. These problems seem to be fairly well resolved for samples containing inorganic selenium, while in the case of organic selenium they are resolved to a lower extent. The suitability and potential of electrochemical and spectrometric techniques in this field are demonstrated. Despite great achievements, further development is required, especially if validated routine procedures are to be executed for more and more informative characteristics of dietary supplements.