Determination of Mercury in Electrolytic Iron Powder by Hydride Generation Atomic Fluorescence Spectrometry with Matrix Matching

The sample of electrolytic iron powder was digested hermetically with 50% (φ) nitric acid solution in a boiling water bath. The effect of coexisting ions and electrolytic iron powder matrix on the determination of mercury was studied, and the possible mechanism of the enhancement of mercury atomic fluorescence signal with Fe²⁺ and Fe³⁺ was discussed. As shown by the results, Ag⁺ and Ni²⁺ could quench the atomic fluorescence signal of mercury, and the quenching effect was stronger with the increasing mass concentration of ions. The mass concentration of Fe²⁺ and Fe³⁺ reached 20.0 mg·L^-1, which could significantly enhance the atomic fluorescence signal and cold atomic fluorescence signal of mercury. Fe²⁺ and Fe³⁺ were reduced to iron atoms in the potassium borohydride system, and the excited iron atoms might transfer energy to mercury atoms to enhance their atomic fluorescence signals. In order to eliminate the above interference, mercury in electrolytic iron powder was determined by hydride generation atomic fluorescence spectrometry with matrix matching. It was shown that linear relationship between atomic fluorescence intensity and mass concentration of mercury was found in the range of 0.400-2.00 μg·L^-1, with detection limit (3s) of 0.03 mg·kg^-1. Test for recovery was made by standard addition method, giving results in the range of 90.9%-100%, with RSDs (n=6) of the determined values in the range of 2.4%-4.3%. This method could meet the requirements of appendix F in national standard GB/T 27404-2008.