Removal of Sulfate Interference in the Determination of Bismuth and Thallium by Graphite Furnace Atomic Absorption Spectrometry

摘要

A mixture of ammonium-EDTA, nickel and copper nitrates is suitable as a matrix modifier for the removal of sulfate interference in the determination of bismuth by graphite furnace atomic absorption spectrometry. A mixture of ammonium-EDTA and nickel nitrate is suitable as the modifier for a thallium determination. In the presence of sodium sulfate, the tolerable ashing temperatures for bismuth and thallium were decreased. Although an organic compound, such as EDTA, enhances the interference from sulfate, by the addition of nickel and copper nitrates this interference can be removed. Since analyte and other cations are masked by EDTA, the coexisting sulfates are converted to ammonium salt, which is readily decomposed and eliminated from the furnace during the ashing step. In the presence of these matrix modifiers, the tolerable concentrations of coexisting sodium sulfate for bismuth and thallium were ca. 1000-times greater than those in the absence of the modifier.