Solution-cathode glow discharge under high NaCl concentration: Impact on excitation conditions and analyte transfer processes

Abstract

The Solution-Cathode Glow Discharge (SCGD) is a useful plasma source for elemental analysis, gathering atomization/excitation/ionization capabilities for aqueous solutions with simplicity and low consumption. When combined with Optical Emission Spectrometry (OES), ng/mL limits of detection can be achieved for multiple elements. Additionally, this plasma source presents certain robustness against the presence of dissolved non-analyte ions. Nevertheless, the mechanisms by which the SCGD can transfer the dissolved analytes from the solution into the plasma, and the mechanisms of how concomitant ions in the sample solution affect the performance of the analysis, are still not fully understood. Therefore, fundamental plasma diagnostics of the SCGD are performed in this work, including electrical measurements, electron densities and rotational and excitation temperatures. In particular, these measurements are performed introducing solutions with NaCl concentrations up to 3.5 g/L in order to understand how they affect the atomization/excitation efficiency and the analyte solution-to-plasma transfer processes of the source. The information is correlated with the signal produced by three analytes (Cd, Zn and Cu).