Flow injection determination of Se in dietary supplements using TiO2 mediated ultraviolet-photochemical volatile species generation

Abstract

This paper proposes a method for determination of selenium content in samples of dietary supplements using TiO2 mediated UV-photochemical vapor generation with quartz furnace atomic spectrometric detection. The flow-injection method was optimized for determination of selenium in the form of selenite or selenate ions. The limits of detection of the proposed method are 0.89ngmL−1 and 0.68ngmL−1 for selenite and selenate, respectively. Extraction in neutral medium was used for the leaching of selenate and NaOH solution was used for the leaching of selenite. The methods accuracy was verified against the declared amounts of Se in five different samples of over-the-counter dietary supplements and on NIST SRM 3280. The method was also compared to results achieved with determination by electrothermal atomization atomic absorption spectrometry following microwave decomposition. The recovery of selenium during sample preparation was tested by spiking the tablets prior to extraction and estimated to be approximately 100%. An interference study has been carried out to estimate the effect of concomitant elements on the methods accuracy.