New advances in the enhancement of direct mercury speciation in solid matter on the example of HgCl, CH3HgCl, HgS and HgSO4 using programmable thermal release in combination with electrothermal atomic absorption spectrometry

[Display omitted] •A reliable method for mercury speciation by combining thermal release with element-selective detection has been created.•Shown that separation of the evaporation and atomization zones prevents peak overlap.•It was found that programmable heating ensures baseline separation of the analytes.•Analytical procedure was unified using dilution of the sample with inert carrier. Mercury is considering as hazardous pollutant presented as a number of various species characterized by different migration routes, bioavailability and toxicity. In this regard, the characterization of natural and a fortiori anthropogenic environment by the concentration of various chemical forms of mercury is relevant to assess the degree of its impact on living organisms. From this point of view, solid samples are the most problematic ones due to the need for preliminary extraction of analytes into solution. The promising approach for this purpose is analysis based on a combination of thermal release as separation way with sequential electrothermal atomic absorption spectrometric detection (TR-ETA-AAS). The present work is based on research of the thermal behavior of individual mercury species in argon atmosphere when the evaporation and atomization zones are separated and a programmable heating algorithm is implemented. To unify an analytical procedure the dilution of reference and analyzed samples with aluminum oxide was applied. The developed method allows determination of the species most often found in natural and contaminated environments: mercury (II) chloride, methylmercury chloride, mercury sulfide and sulphate at the level of 0.003–0.030 µg with a reproducibility of 10–25 %,. The trueness of the proposed approach has been confirmed using certified reference material ERM CE464 and spiking method.