Bernhard Radziuk

Direct electrothermal atomic absorption spectrometric analysis of biological samples and its application to the determination of selenium in human liver biopsy specimens

SummaryThe addition of nickel or silver matrix modifiers is shown effectively to control the problem of thermal instability of selenium in liver biopsy specimens applying the direct solid sampling technique in EAAS. It allows the use of ashing temperatures up to 1,100 – 1,200 °C. There is significant interaction between selenium and matrix components in the gas phase which necessitates standardization against solid samples. In fragments weighing 1 mg concentrations of selenium as low as 0.1 g/g may be determined.

Characterization of a pressurizable two-step atomizer for atomic absorption spectrometry ☆

A two-step atomizer consisting of a transversely heated atomization tube with integrated contacts and a cup furnace for sample vaporization was constructed. The system could accommodate tubes of various lengths and it could be operated at selected pressures. There was no physical contact between the tube and the cup and mainly diffusion was responsible for the sample vapour transport from the cup to the tube. Under these conditions there was an unavoidable loss by 40% of the peak area signals due to the gap between the cup and the tube. For a 24-mm tube, characteristic masses were on the average three times lower than for the state of the art transverse heated graphite atomizers (THGA). By de-coupling the processes of analyte vaporization and atomization the dynamic working range could be increased by three to six times using conventional measurements by atomic absorption spectrometry (AAS). In this case the cup temperature and hence the rate of analyte transport from the cup to the tube was controlled such that atom density in the tube did not exceed the linear range of the absorbance measurement. Carrying out clean-out steps at reduced pressure decreased memory effects.

Visualisation and identification of peak exposure events in aluminium smelter pot rooms using hydrogen fluoride and aerosol real-time portable spectrometers

A recently developed novel portable real-time hydrogen fluoride spectrometer was used with an aerosol PM10 spectrometer under a PIMEX telemetric measurement strategy to visualize and identify simultaneous occupational air peak exposure events to hydrogen fluoride and PM10 aerosol sub-fractions in aluminium smelter pot rooms using Søderberg or Prebake anode technologies. The hydrogen fluoride and the aerosol concentration data measured during different work operations are plotted and evaluated applying the synchronised videos and air concentrations measured by the spectrometers. The main point-emission sources of HF and PM10 were identified and assessed. The major finding in the study was that the main source of PM10 and HF was partly open cells in a Søderberg pot room, whereas in a Prebake pot room, the point emissions of the two contaminants were associated with hot bath residues and hot replaced anodes. In order to prevent the simultaneous exposure to HF and PM10 among pot room workers it is important to prevent workers from being close to these point-sources under unfavourable ventilation. Storage of hot residues outside electrolytic cells without any point source ventilation should not occur.