Elevated-pressure solution cathode glow discharge (SCGD) for more sensitive multi-element analysis by optical...

Area of Science:

• Plasma Physics and Chemistry
• Analytical Chemistry
• Spectroscopy

Background:

• Liquid electrode microdischarges, including solution cathode glow discharge (SCGD), have been studied for decades.
• The influence of pressure on microplasma characteristics, particularly for elemental analysis, remains underexplored.
• Traditional SCGD systems often face limitations in sensitivity and matrix effect mitigation.

Purpose of the Study:

• To introduce and characterize a novel laboratory-built pressurized SCGD system.
• To investigate the effect of elevated gas pressure on microplasma properties and performance in optical emission spectroscopy (OES).
• To evaluate the system's efficacy for elemental analysis, focusing on detection limits and matrix effects.

Main Methods:

• Development and implementation of a pressurized SCGD system operating from 1 to 2.4 atm.
• Characterization of microplasma generated in various gases (air, CO2, Ar, He) under different pressures.
• Application of the pressurized SCGD system as an excitation source for optical emission spectroscopy (OES) in elemental analysis.

Main Results:

• Elevated pressure significantly increased emission line intensities (4-fold in air, 3-fold in CO2/Ar, 70% in He).
• Increased pressure shifted the microplasma towards thermodynamic equilibrium, improving atomization and suppressing molecular bands (e.g., N2).
• Detection limits for alkali metals were 1-4 orders of magnitude lower than ICP OES, with other elements also showing significant improvements.

Conclusions:

• The pressurized SCGD system offers a substantial improvement in sensitivity and a reduction in detection limits for elemental analysis.
• Elevated pressure effectively mitigates matrix effects and enhances the signal-to-noise ratio, leading to more reliable analytical results.
• The developed He-SCGD OES method demonstrates high trueness, validated by analyzing real-world samples (highly mineralized waters).