Micro-hollow glow discharge plasma identification of volatile organic compounds

Glow discharge plasmas have a long-standing analytical history as large, stand-alone laboratory scale instruments. In contrast the physical scaling permit microplasma operation at atmospheric pressure while reducing power requirements, thereby permitting mobile analysis. The energetic species in a nonthermal, i.e. "cold" plasma dissociates species of interest and electronically excites the elemental constituents. The atomic emission spectrum serves to identify the compound and ideally its molecular composition with intensity corresponding to concentration. For some operational regimes and species, emission from OH*, CH* and often C2* diatomic radicals is also produced. Such emission further aids compound detection and identification. Detection and identification of acetone, ethanol, heptane, toluene, and nitrobenzene are demonstrated. Limits of detection extend to parts-per-billion levels for some species such as nitrobenzene. Results will be shown for differentiation of classes of organic compounds such as alkanes, aromatics and oxygenates.