Characteristics of Helium Microwave-Induced Atmospheric Pressure Plasma for Fine Particle Analysis

Helium microwave-induced plasma (He-MIP) for trace element analysis is generated by a 2.45 GHz microwave power ( ~ 1 kW) with the Okamoto cavity of the surface wave mode at atmospheric pressure, and an iron excitation temperature and an electron density of the plasma are measured. With 0.8 kW input microwave power, an excitation temperature of 8000 K and the electron density of 2 x 10/cm are obtained. The sample particles in an Al plate which are ablated by a Q-switched Nd:YAG laser (266 nm) or the nebulization of the suspension of Al2O3 powder are introduced into the center of the annular He-MIP through an inner tube of the torch along with the carrier gas (He or Ar). A time-resolved atomic emission spectrometry (AES) is studied for the particulate composition analysis by the laser ablation and the nebulization of suspension. Atomic emission signals derived from the single particles in the size of submicron are observed. The He-MIP AES is detected the non-metal elements with sufficient sensitivity.