Special Issue "Photoionization Mass Spectrometry"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Optics and Lasers".

Deadline for manuscript submissions: closed (15 July 2018)

Special Issue Editor

Guest Editor
Prof. Dr. Totaro Imasaka

Division of International Strategy, Center of Future Chemistry, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
E-Mail
Phone: +81-802-3294
Fax: +81-92-802-2888
Interests: analytical chemistry; analytical instrumentation; analytical science; trace analysis; lasers; non-linear optics; spectrometry

Special Issue Information

Dear Colleagues,

Mass spectrometry is widely used for the measurement of organic compounds. For example, persistent organic pollutants (POPs) in the environment have been successfully measured at trace levels. Currently, an electron ionization source is utilized in mass spectrometry. This approach, however, suffers from several limitations: It is sometimes difficult to observe a molecular ion, which prevents the determination of a molecular weight. To overcome this problem, several ionization techniques have been developed to date, although they have their own limitations. When a light is used as the ionization source, it is possible to solve some parts of these problems. For example, a molecular ion can be observed even for explosives, such as triacetone triperoxide, and sub-femtogram detection limits, have been achieved for polycyclic aromatic hydrocarbons when combined with gas chromatography. There are many approaches of using a laser emitting from the vacuum-ultraviolet to infrared regions, from the femtosecond to nanosecond lasers, and for the gaseous-phase to solid-phase samples (like matrix-assisted laser desorption ionization). In this Special Issue, the Guest Editor welcomes the submission of papers related to state-of-the-art technology of “Photoionization Mass Spectrometry”, not only for basic science, but also for practical applications, such as in environmental and forensic sciences.

Prof. Dr. Totaro Imasaka
Guest Editor

Manuscript Submission Information

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Keywords

  • laser
  • ionization
  • photoionization
  • mass spectrometry
  • analytical instrumentation
  • trace analysis
  • environmental pollutant
  • toxic compound
  • carcinogenic compound
  • explosives
  • nerve agent

Published Papers (5 papers)

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Research

Open AccessArticle Determination of Relative Ionization Cross Sections for Resonance Enhanced Multiphoton Ionization of Polycyclic Aromatic Hydrocarbons
Appl. Sci. 2018, 8(9), 1617; https://doi.org/10.3390/app8091617
Received: 15 July 2018 / Revised: 4 September 2018 / Accepted: 6 September 2018 / Published: 11 September 2018
Cited by 1 | PDF Full-text (3901 KB) | HTML Full-text | XML Full-text
Abstract
Resonance enhanced multiphoton ionization (REMPI) is a powerful method for the sensitive determination of polycyclic aromatic hydrocarbons (PAHs) in gaseous mixtures via mass spectrometry (MS). In REMPI, ions are produced by the absorption of at least two photons including defined electronic intermediate states. [...] Read more.
Resonance enhanced multiphoton ionization (REMPI) is a powerful method for the sensitive determination of polycyclic aromatic hydrocarbons (PAHs) in gaseous mixtures via mass spectrometry (MS). In REMPI, ions are produced by the absorption of at least two photons including defined electronic intermediate states. As a result—unlike other laser-based ionization techniques—spectroscopic selectivity is involved into the ionization process. Nevertheless, these wavelength-dependent ionization rates impede the quantification using REMPI. For this purpose, relative photoionization cross sections (relPICS) give an easy-to-use approach to quantify REMPI-MS measurements. Hereby, the ionization behavior of a single compound was compared to that of a reference substance of a given concentration. In this study, relPICS of selected single-core aromatics and PAHs at wavelengths of 266 nm and 248 nm were determined using two different time-of-flight mass spectrometric systems (TOFMS). For PAHs, relPICS were obtained which showed a strong dependence on the applied laser intensity. In contrast, for single-core aromatics, constant values of relPICS were determined. Deviations of relPICS between both TOFMS systems were found for small aromatics (e.g., benzene), which can be assigned to the differences in UV generation in the particular system. However, the relPICS of this study were found to be in good agreement with previous results and can be used for system-independent quantification. Full article
(This article belongs to the Special Issue Photoionization Mass Spectrometry)
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Figure 1

Open AccessFeature PaperArticle Comparison of the Characteristic Mass Fragmentations of Phenethylamines and Tryptamines by Electron Ionization Gas Chromatography Mass Spectrometry, Electrospray and Matrix-Assisted Laser Desorption Ionization Mass Spectrometry
Appl. Sci. 2018, 8(7), 1022; https://doi.org/10.3390/app8071022
Received: 18 April 2018 / Revised: 7 June 2018 / Accepted: 19 June 2018 / Published: 22 June 2018
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Abstract
Characteristic mass fragmentation of 20 phenethylamine/tryptamine standards were investigated and compared by means of matrix assisted laser desorption/time-of-flight mass spectrometry (MALDI/TOFM), gas chromatography–electron ionization–mass spectrometry (GC-EI/MS) and liquid chromatography–electrospray ionization/mass spectrometry (LC-ESI/MS) methods. As a result, three characteristic peaks ([M]+ and fragments [...] Read more.
Characteristic mass fragmentation of 20 phenethylamine/tryptamine standards were investigated and compared by means of matrix assisted laser desorption/time-of-flight mass spectrometry (MALDI/TOFM), gas chromatography–electron ionization–mass spectrometry (GC-EI/MS) and liquid chromatography–electrospray ionization/mass spectrometry (LC-ESI/MS) methods. As a result, three characteristic peaks ([M]+ and fragments from the Cβ-Cα bond breakage) were found to be unique and contained information useful in identifying 2C series compounds based on the GC-EI/MS method. We found that the protonated molecular ion ([M+H]+) and two types of fragments produced from the α-cleavage and β-cleavage processes were useful mass spectral information in the rapid screening and confirmation of phenethylamine and tryptamine derivatives when ESI/MS and MALDI/TOFMS methods were applied. This assay was successfully used to determine samples that contain illicit drugs. Full article
(This article belongs to the Special Issue Photoionization Mass Spectrometry)
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Open AccessArticle Vacuum Ultraviolet Single-Photon Postionization of Amino Acids
Appl. Sci. 2018, 8(5), 699; https://doi.org/10.3390/app8050699
Received: 29 March 2018 / Revised: 25 April 2018 / Accepted: 27 April 2018 / Published: 2 May 2018
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Abstract
In this study, ultraviolet (UV) laser desorption and vacuum UV single-photon (VUV SP) postionization were performed to ionize and successfully analyze 20 common amino acids. The analytical merit and efficiency of the ionization was compared with those of conventional UV matrix-assisted laser desorption [...] Read more.
In this study, ultraviolet (UV) laser desorption and vacuum UV single-photon (VUV SP) postionization were performed to ionize and successfully analyze 20 common amino acids. The analytical merit and efficiency of the ionization was compared with those of conventional UV matrix-assisted laser desorption ionization (UV-MALDI). A VUV light source (118 nm) was generated from the ninth harmonic of a Q-switched Nd:YAG laser, and the photon number was determined to be larger than 1012 for each laser pulse in the ionization region. In general, the detection sensitivity of VUV-SP-postionization was 10–100 times higher than that of conventional UV-MALDI. In particular, the ion signal from VUV-SP-postionization was considerably larger than that from UV-MALDI for analytes with low proton affinity such as glycine. However, some fragmentation of intact ions was observed in VUV-SP-postionization. Quantitative analysis performed using a glycine/histidine mixture and tryptophan/phenylalanine mixture revealed that the dynamic range of VUV-SP-postionization was one order of magnitude larger than that of UV-MALDI, indicating that VUV-SP-postionization is suitable for the quantitative analysis of amino acids. Full article
(This article belongs to the Special Issue Photoionization Mass Spectrometry)
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Graphical abstract

Open AccessArticle Matrix-Assisted Laser Desorption Ionization Mass Spectrometry of Compounds Containing Carboxyl Groups Using CdTe and CuO Nanoparticles
Appl. Sci. 2018, 8(4), 492; https://doi.org/10.3390/app8040492
Received: 14 February 2018 / Revised: 23 March 2018 / Accepted: 23 March 2018 / Published: 26 March 2018
Cited by 1 | PDF Full-text (14141 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Matrix-assisted laser desorption ionization mass spectrometry of compounds containing carboxyl groups was carried out by using semiconductor nanoparticles (CdTe and CuO) as the matrix. Salicylic acid (Sal), glucuronic acid (Glu), ibuprofen (Ibu), and tyrosine (Tyr) were ionized as deprotonated species (carboxylate anions) by [...] Read more.
Matrix-assisted laser desorption ionization mass spectrometry of compounds containing carboxyl groups was carried out by using semiconductor nanoparticles (CdTe and CuO) as the matrix. Salicylic acid (Sal), glucuronic acid (Glu), ibuprofen (Ibu), and tyrosine (Tyr) were ionized as deprotonated species (carboxylate anions) by using electrons ejected from CdTe after the photoexcitation. When CuO was used as the matrix, the peak intensity of Tyr became high compared with that obtained with CdTe. Measurements of model peptides, angiotensin II (AngII) and substance P (SubP), were also carried out but the obtained peak intensities were very low. In order to explain this result, the interaction between CdTe and AngII was confirmed by diffuse reflectance spectroscopy. The results suggest that electrostatic binding between semiconductor nanoparticles and AngII prevented the efficient desorption of AngII into the gas phase. Full article
(This article belongs to the Special Issue Photoionization Mass Spectrometry)
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Open AccessFeature PaperArticle Development of Multiphoton Ionization Time-of-Flight Mass Spectrometry for the Detection of Small Emulsion Droplets
Appl. Sci. 2018, 8(3), 413; https://doi.org/10.3390/app8030413
Received: 29 January 2018 / Revised: 1 March 2018 / Accepted: 8 March 2018 / Published: 11 March 2018
Cited by 1 | PDF Full-text (1555 KB) | HTML Full-text | XML Full-text
Abstract
A system for measuring small oil droplets in an oil-in-water (O/W) emulsion was developed using multiphoton ionization time-of-flight mass spectrometry. In the present study, a capillary column with an inner diameter of 15 µm was used for sample introduction. Moreover, a compact microscopic [...] Read more.
A system for measuring small oil droplets in an oil-in-water (O/W) emulsion was developed using multiphoton ionization time-of-flight mass spectrometry. In the present study, a capillary column with an inner diameter of 15 µm was used for sample introduction. Moreover, a compact microscopic system was constructed for observing an emulsion flowing through a capillary column. As a result, the length for sample introduction was shortened, which is preferable for the direct evaluation of an emulsion. Using this system, the minimum diameter of a detectable toluene droplet in an O/W emulsion was decreased to 1.7 µm. The present system could be used to evaluate the local microenvironment and stability of an emulsion. Full article
(This article belongs to the Special Issue Photoionization Mass Spectrometry)
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Graphical abstract

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