An investigation of micro-hollow cathode glow discharge generated optical emission spectroscopy for hydrocarbon detection and differentiation

The analytical utility of a micro-hollow cathode glow discharge plasma for detection of varied hydrocarbons was tested using acetone, ethanol, heptane, nitrobenzene, and toluene. Differences in fragmentation pathways, reflecting parent compound molecular structure, led to differences in optical emission patterns that can then potentially serve as signatures for the species of interest. Spectral simulations were performed emphasizing the CH (A²Δ-X²Π), CH (C²Σ-X²Π), and OH (A²Σ⁺-X²Π) electronic systems. The analytical utility of selected emission lines is demonstrated by a linear relationship between optical emission spectroscopy and parent compound concentration over a wide range, with detection limits extending down to parts per billion (ppb) levels.