Detection of technetium in electrothermal atomic absorption spectrometry using coincident emission lines of other elements

Abstract

Spectral lines of 16 elements emitted by hollow cathode lamps were observed to overlap with those Tc lines which are appropriate for atomic absorption measurements. Analytically useful sensitivity was found with an emission line source of Pd I at 371.89, La II at 403.17, Cd I at 346.62, Hf I at 374.68 and Ni I at 358.79 nm, which partially overlap with non-resonant lines of the low energy levels of Tc. Significantly lower sensitivity was found with the emission lines of Pb I at 261.42 and Tm II at 313.12 nm, which overlap partially with resonant lines of Tc. The thermal pre-treatment curve of Tc showed a marked dip in the temperature range 400–900 °C with a minimum at 700 °C. The Tc absorption signal increased up to 1100 °C and remained essentially constant up to 1800 °C (without any chemical modifier). A striking similarity of the thermal pre-treatment curve with respect to the dip was observed also for Re. The optimum atomization temperature for Tc was 2700 °C at a pre-treatment temperature of 1200 °C. Atomization from the pyrolytic graphite platform resulted in significantly lower Tc signals. Calibration graphs for the peak height absorbance and integrated absorbance were linear up to about 30 and 50 ng of Tc, respectively. Characteristic mass values of 0.8 ng of Tc for the integrated absorbance and 0.34 ng of Tc for the peak height absorbance measurements and a detection limit of 2 ng of Tc (3σ, n= 10) with wall atomization and the Pd hollow cathode 371.9 nm line source were obtained in terms of absolute mass.