Micro-hollow glow discharge analysis of carbonaceous materials

Combustion produced soot can vary widely in composition, in particular C/H ratio, reflecting both its molecular origins and temperature of evolution. In this study the main objective was to develop and demonstrate a micro-hollow glow discharge analyzer coupled to a miniature spectrometer for a variety of carbonaceous materials. Traditional sputtering capability of the glow discharge has been utilized for both atomizing and electronically exciting the samples for stand-alone analytical analysis. Analyzed samples included flame and diesel soot, biochars and a carbon black. Demonstrating versatility for chemistry analysis, the plasma detector could distinguish carbonaceous materials with different C/H ratios and recognize heteroelements, inorganics and metal elements from carbonaceous materials. For some operational regimes and species, emission from OH (A²∑⁺-X²∏), CH (A²Δ-X²∏), and often C₂ (d³∏_g-a³∏_u; Swan band system) diatomic radicals is produced. Moreover the inherent oxygen content nascent to the carbonaceous material can be quantitatively estimated without any heat treatment, besides having the light element detection capability, in particular hydrogen.