Liangyuan Jia

Vacuum Ultraviolet Photofragmentation of Sarcosine: Photoionization Mass Spectrometric and Theoretical Insights

Vacuum ultraviolet (VUV) photon-induced ionization and fragmentation of N-methyl glycine (sarcosine) were investigated with infrared laser desorption/tunable synchrotron VUV photoionization mass spectrometry (IR LD/VUV PIMS) and theoretical calculations. Fragment-controllable mass spectra of sarcosine were measured at various photon energies. By tuning the photon energy, the fragments at m/z 44, 45, 43, 42, 30, and 60 were gradually detected. The ionization energy of the precursor was obtained by measuring the photoionization efficiency spectrum. Possible formation pathways of the fragment ions at m/z 44 (CH(3)NHCH(2)(+)), 45 (CH(3)NH(2)CH(2)(+)), 43 (CH(2)NHCH(2)(+)), 42 (CH(2)NCH(2)(+)), 30 (CH(2)NH(2)(+)), and 60 (CH(2)COOH(2)(+)) were discussed in detail with the help of calculations at the G3B3 and B3LYP/6-31++G(d,p) levels.

VUV photon‐induced ionization/dissociation of antipyrine and propyphenazone: mass spectrometric and theoretical insights

Two analgesic and anti-inflammatory drugs, antipyrine and propyphenazone, were investigated with infrared laser desorption/tunable synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (IR LD/VUV PIMS) and theoretical calculations. Mass spectra of the two drugs were measured at various photon energies. Fragment ions were gradually produced as photon energy increases. The structural assignment of the dominant fragment ions was supported by the results from a commercial electron impact time-of-flight mass spectrometer (EI-TOF MS). Primary fragmentation pathways were established from experimental observations combining with theoretical calculations. Methyl radical elimination is a common fragmentation pathway for two analytes. However, for propyphenazone cation, isopropyl group elimination to form antipyrine cation is another competitive pathway.

Study on Gas Phase Components in Mainstream Cigarette Smoke by Synchrotron Radiation Photoionization Mass Spectrometry

Abstract The gas phase components in the mainstream cigarette smoke were investigated by tunable synchrotron vacuum ultraviolet (VUV)/photoionization mass spectrometry (PIMS). First, the smoke was collected by a modified glass syringe. Photoionization mass spectra for the smoke were obtained directly on-line, without pretreatment and separation. Second, ionization energies (IE) of the components at each mass-to-charge ratio ( m / z ) were obtained by scanning the photoionization efficiency (PIE) spectra. The possible components could be assigned by comparing the experimental IE with known NIST database. Final, the puff-by-puff resolved behaviors of some components were studied by using a modified commercial smoking machine combined with PIMS.

VUV Photoionization and Dissociation of Tyramine and Dopamine: the Joint Experimental and Theoretical Studies

Photon induced dissociation investigations of neutral tyramine and dopamine are carried out with synchrotron vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. At low photon energy only molecular ions are measured by virtue of nearthreshold photoionization. While increasing photon energy to 11.7 eV or more, four distinct fragment ions are obtained for tyramine and dopamine, respectively. Besides, the ionization energies of tyramine and dopamine are determined to be 7.98±0.05 and 7.67±0.05 eV by measuring the photoionization efficiency curves of corresponding molecular ions. With help of density function theory calculations, the detailed fragmentation pathways are established as well. These two molecular cations have similar aminoethyl group elimination pathways, C7H8O2+· (m/z=124) and C7H8O+· (m/z=108) are supposed to be generated by the McLafferty rearrangement via γ-hydrogen (γ-H) shift inducing β-fission. And CH2NH2+ is proposed to derive from the direct fission of C7-C8 bond. Besides, the McLafferty rearrangement and the C7-C8 bond fission are validated to be dominant dissociation pathways for tyramine and dopamine cations.

Novel applications of synchrotron VUV photoionization mass spectrometry in combustion and energy research

Combustion of fossil fuels provides more than 80% of the global energy supply nowadays. However, the rapid consumption of fossil fuels has raised great public concerns on energy sustainability and environmental security. Since chemical reactions play the crucial role in combustion and other thermal chemical processes in energy conversion, prior understanding of the chemical reaction mechanisms in these processes is essential for exploring new techniques to improve combustion efficiency and reduce pollutant emissions. This paper reviews our recent efforts in the development of new methods and instruments with synchrotron vacuum ultraviolet (VUV) photoioni- zation mass spectrometry and their applications in combustion and energy research, and presents perspectives of novel methods and applications in the near future.Combustion of fossil fuels provides more than 80% of the global energy supply nowadays. However, the rapid consumption of fossil fuels has raised great public concerns on energy sustainability and environmental security. Since chemical reactions play the crucial role in combustion and other thermal chemical processes in energy conversion, prior understanding of the chemical reaction mechanisms in these processes is essential for exploring new techniques to improve combustion efficiency and reduce pollutant emissions. This paper reviews our recent efforts in the development of new methods and instruments with synchrotron vacuum ultraviolet(VUV) photoioni- zation mass spectrometry and their applications in combustion and energy research, and presents perspectives of novel methods and applications in the near future.

Experimental and Theoretical Study on Pyrolysis of Isopsoralen

The pyrolysis of isopsoralen was studied by synchrotron vacuum ultraviolet photoionization mass spectrometry at low pressure. The pyrolysis products were detected at different photon energies, the ratios of products to precursor were measured at various pyrolysis temperatures. The experimental results demonstrate that the main pyrolysis products are primary CO and sequential CO elimination products (C10H6O2 and C9H6O). The decomposition channels of isopsoralen were also studied by the density functional theory, then rate constants for competing pathways were calculated by the transition state theory. The dominant decomposition channels of isopsoralen and the molecular structures for corresponding products were identified by combined experimental and theoretical studies.