Time-Gated Pulsed Glow Discharge:  Real-Time Chemical Speciation at the Elemental, Structural, and Molecular Level for Gas Chromatography Time-of-Flight Mass Spectrometry

Abstract

A millisecond pulsed glow discharge is used as a versatile ion source for time-gated generation of elemental, structural, and molecular ions. The utility of this ion source for comprehensive chemical analysis of a series of aromatic and halogenated hydrocarbons is illustrated in this manuscript. To highlight the analytical utility of this transient ion source, it was connected to a gas chromatograph for the mass spectrometric determination of mixtures containing benzene, toluene, o-xylene, cymene, tert-butylbenzene, carbon tetrachloride, chloroform, chlorobenzene, tetrachlorethane, and dichlorobenzene. Explicit chemical analysis was accomplished by introducing the GC eluent into a pulsed glow discharge operating at a rate of 100 Hz with a 50% duty cycle. Using three independent digitizers for time-gated acquisition in three separate time regimes, nearly concurrent collection of elemental, structural, and molecular information was accomplished. In general, elemental information was obtained during the first 0.015 ms after the plasma onset; structural information, as ascertained from molecular fragmentation, was obtained during the plateau time regime when the plasma pulse is at a steady state, whereas molecular M(+) and MH(+) ions were obtained during the afterpeak time regime, that is, after the cessation of the plasma power pulse.

Analysis of small bubbles in glass by glow discharge—Time-of-flight mass spectrometry

“…4 atomic ion signals from oxygen, nitrogen and carbon can be observed. The ratio between 16 O + and 32 (O 2 ) + turned out to be rather similar to that obtained by electron impact [21]. However, much higher signals were obtained in our system for the atomic nitrogen than for the molecular ion (N 2 + ).…”

“…As can be observed, similar signals for elemental and molecular ions were achieved at 10 W, while for 15 and 20 W the elemental ion signals turned out to be much higher than the molecular ones. Moreover, it should be noted that the use of 20 W gave rise to lower 16 O + and 32 (O 2 ) + signals than at 15 W forward power. As can also be observed in Fig.…”

“…However, time-of-flight mass spectrometers (TOFMSs) are being increasingly used due to their high sampling rate and ability to collect complete mass spectra without loss of precision or sensitivity [15]. Moreover, during the last years the analytical capabilities of a GD coupled to a TOFMS have been investigated for the analysis of organic species in gaseous form [16][17][18].…”

Tunable fragmentation of organic molecules in laser ablation glow discharge time-of-flight mass spectrometry

“…The mass spectra acquired in the afterglow showed intact parent molecules of the analyte and no major fragmentation was reported, which is an indication of a soft ionization process. In another report by Lewis et al [18], the successful analysis of aromatic compounds such as o-xylene using a pulsed GD-TOFMS coupled to gas chromatography (Ar as the carrier) was reported. A pulsed GD coupled to a gas chromatography system was also reported by Fliegel et al [19], where elemental and molecular information from gaseous analytes such as toluene in methanol as solvent was demonstrated.…”

Inorganic mass spectrometry as a tool for characterisation at the nanoscale

“…Pulsed rf-GDs are particularly advantageous for the analysis of heat-sensitive materials, such as glasses and polymers [58,59]. Studies on pulsed rf-GDs coupled with MS are still scarce, although the combination with TOFMS is particularly promising.…”