Analysis of Different Valence States of Selenium in Geological Samples by Hydride Generation-Atomic Fluorescence Spectrometry

An analysis method was established for the determination of Se(Ⅳ) and Se(Ⅵ) in soil samples by Hydride Generation-Atomic Fluorescence Spectrometry (HG-AFS), the key point being the selection of the extraction agent. In the past, there were so many kinds of extraction agents, but no pertinence. The extraction capacity of different extraction agents was compared and KH₂PO₄-K₂HPO₄ solution was selected for the experiment, which has a pH value of 8.5. The total content of Se was measured by using 6 mol/L HCl as reducing agent and being heated in a boiling water bath for 30 min. The content of Se(Ⅳ) was measured by the solution without heating in the boiling water bath. Finally, the content of Se(Ⅵ) was yielded by total Se content subtracted from the Se(Ⅳ). In the acidity condition of this experiment, the interference of coexisting elements was eliminated by adding Fe(Ⅲ) salt. The relative standard deviation was 5.0%-12.6% (n=11), linear range was 0.00-6.00 μg/L, the recovery was 90.0%-112.5% and the detection limit was 0.347 μg/L. The method has been applied to determinate trace Se in reference materials and the results were in agreement with certified values. The results indicate that the method is simple, quick and highly sensitive. It is a feasible method to detect different valence states of Se in soil samples.