Inductively Coupled Plasma-Mass Spectrometric Analysis of Mercury in Biological Samples and Interference Correction Methods

Inductively coupled plasma-mass spectrometry (ICP-MS) is difficult to determine Hg in biological samples directly and accurately due to polyatomic interferences, such as tungsten oxide, and matrix effects. We established ICP-MS method for the determination of Hg in biological samples based on using the kinetic energy discrimination (KED) mode combined with mathematical correction and internal standard correction. In this experiment, spectral interferences of Hg in standard (STD) mode and KED mode was investigated. ²⁰²Hg was selected as the analyzed isotope in the KED mode effectively reducing but not completely eliminating the interference. It was found that the interference amount of W with Hg was linearly related to the concentration of W (R²=0.9997). The matrix interference was eliminated with internal standard (Rh concentration of 50μg/L) and sample dilution (dilution of 100 times). The reliability of the method has been tested by 9 reference materials, and the results were in agreement with certified value (or reference value). In particular, the accuracy of GBW10028 (Astragalus membranaceus), GBW10025 (spirulina) and GBW10015a (spinach) has been significantly improved. The relative standard deviation (n=10) was 0.7% to 7.0%. The method is suitable for the analysis of Hg in biological samples.