Enhanced Microplasma Excitation Source Using Fiber-Tip Discharge Clusters with Low Breakdown Voltage for Miniaturized Optical Emission Spectroscopy

Abstract

Microplasma based optical emission spectrometry (OES) holds great promise for field elemental analysis, yet its practical application is hindered by limited excitation capability and high breakdown voltage constrained by millimeter-scale discharge geometries. Herein, we report an enhanced fiber-tip discharge microplasma excitation source constructed from carbon felt electrodes, enabling simultaneous multielement analysis of microliter-scale samples. During discharge, sharp tips are generated at the ends of micrometer-scale carbon fibers at the carbon felt interface, providing abundant high-field sites and promoting initial ionization. The resulting multitip configuration provides densely distributed fiber-tip discharge sites, reducing the breakdown voltage and improving local energy deposition for analyte excitation. By integrating sample loading, drying of the preloaded carbon felt electrode, and in situ excitation, the system enables efficient analysis of 50 μL solution samples. Under the same operating conditions, the carbon felt electrode pair provided clearly detectable multielement emission signals that were difficult to obtain using conventional point discharge electrode configurations. This strategy was applied to the simultaneous determination of Cr, Mn, Cd, and Pb, covering hydride-forming and nonhydride-forming elements, with limits of detection (LODs) of 0.3, 0.1, 0.2, and 0.2 μg L–1, respectively, and relative standard deviations (RSDs) below 5% (n = 11). The accuracy and applicability were validated through analysis of certified reference materials and real samples. With its compact configuration, low sample requirement, and reliable analytical performance, this method shows promise for on-site elemental analysis. This work provides an electrode-interface engineering strategy for rapid multielement screening of trace samples and portable heavy metal analysis.