Characterization of a co-planar dielectric barrier discharge design as a plasma source for trace element detection by atomic spectrometry

Abstract

Dielectric barrier discharges (DBD) are used in analytical chemistry for the dissociation of molecules, which can then be detected with methods like atomic absorption spectroscopy or emission spectroscopy. However, a drawback of this approach is that the analyte can be deposited on the reactor walls, lowering the density available for element detection. In this work, we propose a novel design of a DBD for element detection which consists of a T-shaped quartz glass body with line-shaped co-planar electrodes. This co-planar configuration was selected to force the discharge towards the glass surface, thus increasing the release of deposited analyte from the reactor walls. This was verified by temporally and spatially resolved optical emission spectroscopy showing that the plasma propagates in a bent structure, close to the wall between the electrodes. The optical results also point towards the importance of helium metastable states in the dissociation of molecules. Thus, spatially resolved metastable densities were measured by tunable diode laser absorption spectroscopy. The metastable density was in the order of 4.5×1010cm−3, and the density profile correlated with the bent structure observed in the emission measurements.