UV-photochemical vapor generation with quartz furnace atomic absorption spectrometry for simple and sensitive determination of selenium in dietary supplements
Abstract
This study describes the optimization and quantification of UV-photochemical vapor generation using the Se(IV) standard, together with application of the proposed technique for practical purposes. The generation process was performed in continuous mode and was combined with atomic absorption spectrometry utilizing an externally heated quartz furnace as an atomizer.
Formic acid with a concentration of 0.5 mol L-1 acted as the photochemical agent during the UV-assisted conversion of Se(IV) from the condensed to the gaseous phase; no further chemicals were needed. A very low limit of detection (LOD) 40 ng L-1 was achieved under the optimum experimental conditions and the repeatability expressed as % RSD was 1.8% at 5 mu g L-1 Se(IV).
Analysis of the certified reference NIST SRM 1643e was performed to demonstrate the accuracy of the method with good correlation between the certified and experimentally achieved value. The effect of various coexisting ions on the selenium signal was also investigated.
Finally, commercially available dietary supplements containing selenium in the form of inorganic Se(IV) and Se(VI) were analyzed. The yields attained using only simple ultrasonic-assisted extraction of Se compounds from the samples by deionized water did not differ by more than 15% compared to the producers of declared contents of selenium for four of the five samples tested.