Photoionization studies on various quinones by an infrared laser desorption/tunable VUV photoionization TOF mass spectrometry

Abstract

Photoionization and dissociative photoionization characters of six quinones, including 1,2-naphthoquinone (1,2-NQ), 1,4-naphthoquinone (1,4-NQ), 9,10-phenanthroquinone (PQ), 9,10-anthraquinone (AQ), benz[a]- anthracene-7,12-dione (BAD) and 1,2-acenaphthylenedione (AND) have been studied with an infrared laser desorption/tunable synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (IR LD/VUV PIMS) technique. Mass spectra of these compounds are obtained at different VUV photon energies. Consecutive losses of two carbon monoxide (CO) groups are found to be the main fragmentation pathways for all the quinones. Detailed dissociation processes are discussed with the help of ab initio B3LYP calculations. Ionization energies (IEs) of these quinones and appearance energies (AEs) of major fragments are obtained by measuring the photoionization efficiency (PIE) spectra. The experimental results are in good agreement with the theoretical data.

Gas‐phase dissociation of 1,4‐naphthoquinone derivative anions by electrospray ionization tandem mass spectrometry

“…[23] Electrospray ionization tandem mass spectrometry (ESI-MS/MS) through CID has been employed to characterize some protonated derivatives of 1,4-naphthoquinone, where the presence of a hydrogen atom in the lateral chain characterizes the fragmentation pathways. [24] For such studies, however, previous knowledge of the fragmentation pathways of a series of compounds exhibiting a conserved structural core is often necessary.…”

Photoionisation and photodissociation studies of nonvolatile organic molecules by synchrotron VUV photoionisation mass spectrometry and theoretical calculations

“…The instrument of IR LD/VUV PIMS has been reported elsewhere [49,55,57]. Therefore, only a short description is given here.…”

“…The acceleration voltage was kept at 2000 V. The time delay between the Nd:YAG laser and the pulse of the extract field was 150 ms, which was controlled by a home-made pulse/delay generator. The time series between the Nd:YAG laser and the extractor field and multiscaler start is shown in Figure 3(b) [57]. The ion signals were detected with microchannel plates (MCP), and then amplified by a preamplifier (VT120C, ORTEC, USA).…”

“…A gas filter filled with neon or argon was used to eliminate higher order radiation. The average photon flux was measured to be around (a) Schematic setup of an IR laser desorption/VUV photoionisation mass spectrometry À the substrate was placed between the repeller and extractor plates [57]; and (b) time series between the Nd: YAG laser and the extractor field and multiscaler start [57].…”

“…The samples are then ionised by a crossed VUV light, resembling the operation manner of L2MS. The IR LD/VUV PIMS has been successfully applied for the studies of a variety of small compounds, including polycyclic aromatic hydrocarbons (PAHs), amino acids [52,53], steroids [54], drugs [55], quinones [56,57], DNA bases and complex mixtures [58].…”