A crossed hollow electrode point discharge for highly efficient vapor sample introduction and spectral excitation

Discharge microplasma has been popularly utilized as the crucial component of excitation source for miniaturized optical emission spectrometer. However, its overall excitation capability and efficiency are still limited due to the reduction of size and power, thus limiting its wide field analytical applications.

A new compact microplasma excitation source was constructed by using a crossed hollow electrode point discharge for a miniaturized optical emission spectrometer, with achieving both highly efficient vapor sample introduction and spectral excitation. Two pairs of electrodes were arranged crossly in a coplanar mode, and one of the four electrodes was with a hollow structure. In the discharge chamber, the plasma region was overlapped and greatly enlarged, which improved the overall excitation capability. Meanwhile, the hollow electrode was also used as the introduction tube for sample vapor; thus, all the gaseous analyte could be confined into the plasma region for full excitation and improved excitation efficiency. Through coupling with hydride generation for vapor sample introduction, under the selected conditions, As, Ge, Hg, Pb, Sb, Se, and Sn could be efficiently excited for optical emission detection, with limits of detection of 1.8, 0.7, 0.1, 0.4, 0.8, 6.2, and 0.1 μg L^-1, respectively, and with relative standard deviations all less than 4 % (n = 5). Compared to conventional point discharge microplasma with a single pair electrodes, the analytical sensitivities for the test elements were improved by 3-5 times. Certified Reference Materials were successfully analyzed with this miniature device to demonstrate its accuracy and availability.

This study provided an effective strategy to improve the excitation capability and efficiency of point discharge microplasma source for high-performance miniaturized optical emission spectrometric instruments. It features additional advantages of compactness, low power consumption and simple operation, thus showing potential prospects in fast field elemental analysis.