Use of Penning Ionization Electron Spectroscopy in Plasma for Measurements of Environmental Gas Constituents

Abstract

A breadboard GC detector based on Penning ionization electron spectroscopy in plasma (PIES) was investigated. The PIES detector was set up in series with a gas chromatograph and a thermal conductivity detector. Two-dimensional PIES chromatograms were recorded for carbon monoxide, carbon dioxide, and methane. The analytes were identified independently of the GC retention time, and their concentrations were measured in a range between 1 and 100 ppm. PIES spectra for methane were observed for the first time and displayed two characteristic peaks with electron energies of 7.1 and 5.4 eV. Rate coefficients for Penning ionization due to collisions between 2(3)S helium metastable atoms and analyte molecules under study were found to be k*(CO) = (0.7 +/- 0.2) x 10(-10), k*(CO2) = (1.8 +/- 0.7) x 10(-10), k*(7.1 CH4) = (4.7 +/- 0.6) x 10(-10), and k*(5.4 CH4) = (8 +/- 2) x 10(-10) cm(3)/s. The work provides the basis for the development of a portable and robust analytical platform capable of in situ real-time monitoring of greenhouse gases, with a perspective toward laboratory-on-chip realization.