"Preconcentration of oxidized mercury (HgII) species is currently a bottleneck for comparable and traceable atmospheric Hg speciation. Preconcentration of HgII species is mostly performed by three different approaches: KCl-coated denuders, sorbent membranes (i.e. cation-exchange membranes and nylon membranes) and sorbent traps (KCl crystal traps). The different characteristics of these preconcentration methods and the results obtained with them may lead to questionable metrological comparability of the results. Comparability can be achieved by calibrating different preconcentration methods with System of Units (SI) traceable calibration. SI traceable calibration has recently been developed and is based on the non-thermal plasma oxidation of Hg0 to HgII in the presence of He and reaction gas (O2, Cl2 or Br2).
In our work, we used the newly developed gaseous HgII calibration based on the non-thermal plasma approach in combination with different HgII preconcentration methods. This way we assessed the possible differences between the methods and their advantages and drawbacks. Preconcentration methods were also tested for the stability of loaded HgII under different conditions that simulated real-time sampling. Due to its specificity and sensitivity, 197Hg radiotracer (obtained by irradiation of enriched 196Hg solution) was used to enable experiments with ambient concentration levels. In addition, the internal calibration of the most commonly used atmospheric Hg speciation unit produced by Tekran (Hg0-based calibration) was compared with the plasma oxidation calibration approach (HgII-based calibration)."
Authors: Jan Gačnik, Igor Živković, Jože Kotnik, Sreekanth Vijayakumaran Nair, Uroš Cvelbar, Milena Horvat