A radially confined point discharge microplasma for a miniaturized optical emission spectrometer

Abstract

A novel radially confined point discharge microplasma for a miniaturized optical emission spectrometer (RC-PD-OES) with high excitation capability was fabricated by arranging a hollow electrode and a tungsten rod electrode perpendicularly in a T-shaped quartz tube with a small inner diameter. The analyte-containing vapor was introduced into the microplasma region through the hollow electrode, and the narrow quartz tube limited its radial diffusion, enabling it to completely interact with the microplasma, thus achieving sufficient atomization and excitation. The emission spectral characteristics and plasma parameter diagnostics of two PD devices with different physical sizes further demonstrated that the radial confinement effect could enhance the excitation capability of the microplasma. The hollow electrode and the W rod electrode were placed perpendicularly to collect stronger spectral emission signals from the axial view. Combined with hydride generation (HG) for sample introduction, the RC-PD-OES was used for the highly sensitive determination of As, Sb, Ge, Pb, Hg, Se, and Sn. Under the selected conditions, the limits of detection (LODs) for As, Sb, Ge, Pb, Hg, Se, and Sn were 1, 0.4, 0.5, 0.06, 0.09, 6, and 0.2 μg L⁻¹, respectively, and the relative standard deviations (RSDs) were all less than 3.3%. The proposed HG-RC-PD-OES features simplicity, compactness, high sensitivity and robustness, making it promising for field analysis of these trace elements.