4.3.4. Heavy Metals

The content of trace elements (heavy metals) in chars from biomass was determined with the use of the IChPW's internal procedure. Analyzed samples were firstly dissolved in concentrated acids (HNO3 and HF) using a closed circuit, multistage microwave-assisted mineralization process. For this purpose, a 10-position microwave mineralizer Ethos 1 from Milestone was used. The maximum temperature of the mineralization was equal to 200 ◦C. Dissolved samples were analyzed using an inductively coupled plasma optical emission spectroscope (ICP-EOS) iCAP 6500 DUO from Thermo Fisher Scientific. For calibration of the EOS, single element standards from SCP Science were used.
