Interference Sources and Elimination Methods for the Determination of Selenium in Soil and Water Sediment by Atomic Fluorescence Spectrometry

Abstract

BACKGROUND Atomic Fluorescence Spectrometry (AFS) has advantages of high sensitivity, simple structure and easy operation, but the digestion process of the standard analysis method for determination of Se in soil is cumbersome and readily produces interference. OBJECTIVES To evaluate the applicability of Se determination in soil and sediment by water bath digestion/AFS, and uncover the main interference and elimination methods. METHODS Based on the standard method of GB/T 22105-2008, boiling water bath of aqua regina was used to digest Se in soil and sediment. Four treatments, including Fe3+, concentrated hydrochloric acid, Fe3+with concentrated hydrochloric acid, and water bath solution, were used to eliminate the interference of Cu2+ and Pb4+. RESULTS The detection limit of Se by this method was 0.008mg/kg, the relative standard deviation of the test reference materials was 0.5%-11%, and the relative error was -16.3%-9.5%, better than the detection limit (0.01mg/kg), precision (0.79%-23.1%) and accuracy of the industry standard HJ 680-2013. CONCLUSIONS According to the experiment, it is proposed to add concentrated hydrochloric acid to the water bath digestion solution without adding thiourea-ascorbic acid. By increasing the acidity and Cl- concentration of the solution and keeping the concentration of hydrochloric acid in the sample higher than 23%, the reduction of Cu2+ to Cu0 and Pb4+ to form PbH4 can be inhibited. The negative interference of Cu and the positive interference of Pb are effectively reduced, and the precision and accuracy of Se measured by AFS are improved.

Keywords

• soil
• sediment
• water bath digestion
• selenium
• atomic fluorescence spectrometry
• interference elimination