Determination of Mercury and Other 6 Elements in Soil and Sediment by Inductively Coupled Plasma Tandem Mass Spectrometry with Oxygen Dynamic Reaction

The determination of mercury in soil and sediment held a low accuracy by inductively coupled plasma mass spectrometry (ICP-MS) due to high ionization energy and low ionization efficiency of mercury element, and polyatomic ion interference of tungsten oxides or hydroxides (WO⁺ and WOH⁺). Herein, inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) was applied to the analysis with ²⁰²Hg selected as the test isotope. Under MS/MS reaction mode, the introduction of oxygen in dynamic reaction cell could reduce interference of mass overlap for mercury owing to the reactions of electron transfer, dehydrogenation and oxygenation of WO⁺ and WOH⁺. When the oxygen flow rate was 2.8 mL·min^-1 and the mass cutting parameter was 0.55, the BEC of the 1.00 mg·L^-1 tungsten standard solution at m/z 202 was 0.003 μg·L^-1, which was 99.9% lower than that produced by the standard mode (MS/MS). Under optimized test conditions, the detection limit (3s) of mercury was 0.001 mg·kg^-1. The relative errors of the certified reference materials were in the range of -12%-17%, and RSDs (n=6) of the determined values were 2.2%-4.8%. This method could meet the requirement for the determination of mercury in soil and sediment, and was applied to the determination of other elements including arsenic, selenium, silver, cadmium, antimony, and bismuth.