Removal of traces of mercury from a carrier gas for analytical purpose

Background The analysis of mercury by cold vapor requires a gas, usually argon or helium, to transport elementary mercury to the gold trap or directly to the detector. When analyzing mercury in environmental matrices, a gas with a metal concentration as low as a few picograms per cubic meter is needed. Different sorbents have been used to purify the gas for a long time, but little information is available about them, mainly considering the analytical purpose. This paper presents results of the absorption capacity for solids and hypochlorite solutions that usually are used as mercury sorbents, giving technical information to the analyst to decide the best gas cleaning process to be used. Findings The absorption capacities of different sorbents were tested using atomic fluorescence spectrometry. Among the tested solids, platinum presented the highest absorption capacity (13.04 pg Hg per gram of Pt). Interaction between sodium hypochlorite, sodium chloride, and EDTA in the absorption capacity was investigated by a 2 3 factorial design. Results showed a significant interaction between hypochlorite and chloride. Conclusions A solution of 1.26 mmol L −1 sodium hypochlorite, 0.48 mol L −1 sodium chloride, and 0.6 mmol L −1 EDTA shows the highest absorption capacity (167.3 pg Hg) among the tested compositions. That solution has eliminated even traces of mercury from gases, resulting in a carrier free of mercury, what cannot be achieved using the solid sorbents tested, despite the use of solutions which is more tedious than the use of solids to clean gas. Anyway, the hypochlorite solution shows to be a good option to clean gases that have to be used in the analysis of mercury in samples with very low concentration.