Evaluating the performance of oxidized Hg reference gas generators in the range ng m⁻³ to µg m⁻³ by improved coupling with ICP-MS

We demonstrate a novel way to introduce a so-called Hg reference gas, produced by a gas generator, into an elemental detector, such as ICP-MS, and to directly measure gaseous oxidized mercury (GOM as HgCl₂) at a wide range of concentrations, covering 4 orders of magnitude. The approach was tested using two types of generators based on the dilution of a gas saturated with mercury chloride vapours (from dry HgCl₂ salt) and on the evaporation of aqueous HgCl₂ standards. The former generator provided reference gas at µg m⁻³ concentrations, while the latter was applicable from low ng m⁻³ to µg m⁻³. The generation and measurement of gaseous Hg was achieved in real time without significant memory effects, and with a response time shorter than 5 min. This unique approach of direct measurement (without thermal conversion) of both gaseous elemental mercury (GEM) and GOM from environmentally relevant to industrial concentrations has been shown to offer the potential to significantly improve the reliability of Hg determination from gas generators. This, in the longer term, will be invaluable to improve accuracy of in-field Hg measurements.