Mass Spectrometry
Online ISSN : 2186-5116
Print ISSN : 2187-137X
ISSN-L : 2186-5116
Current issue
Displaying 1-9 of 9 articles from this issue
Original Article
  • Kenzo Hiraoka, Yuji Sakai, Hiroyuki Kubota, Satoshi Ninomiya, Stephani ...
    2023 Volume 12 Issue 1 Pages A0114
    Published: January 31, 2023
    Released on J-STAGE: January 31, 2023
    Advance online publication: December 24, 2022
    Supplementary material

    Among the various types of cluster secondary ion mass spectrometry (SIMS), electrospray droplet impact/secondary ion mass spectrometry (EDI/SIMS) is unique due to its high ionization efficiency and non-selective atomic/molecular-level surface etching ability. In this study, EDI/SIMS was applied to the non-selective etching of synthetic polymers of polystyrene (PS) and poly(9,9-di-n-octylfluonyl-2,7diyl) (PFO) deposited on a silicon substrate. The polymers gave characteristic fragment ions and the mass spectra remained unchanged with prolonged EDI irradiation time, indicating that non-selective etching can be achieved by EDI irradiation, a finding that is consistent with our previous reports based on EDI/X-ray photoelectron spectroscopy analyses. From the irradiation time and film thickness, the etching rates for PS and PFO were roughly estimated to be 0.6 nm/min and 0.15 nm/min, respectively, under the experimental conditions that were used. After the depletion of polymer sample on the surface, ion signals originating from the exposed silicon substrate were observed. This indicates that EDI/SIMS is applicable to the analysis of the interface of multilayered films composed of organic and inorganic materials.

  • Narumi Moromoto, Yosuke Kawai, Kentaro Terada, Masaaki Miyahara, Naoto ...
    2023 Volume 12 Issue 1 Pages A0115
    Published: February 10, 2023
    Released on J-STAGE: February 10, 2023
    Advance online publication: January 13, 2023

    Northwest Africa (NWA) 2977 is a lunar basaltic meteorite that was found in 2005 and has been classified as an olivine cumulate gabbro. This meteorite contains a shock melt vein (SMV) induced by an intense shock event. We report herein on an in-situ analysis of phosphates in the host gabbro and the shock vein for the U–Pb dating of NWA 2977 using an ion microprobe, NanoSIMS. The majority of the analyzed phosphates, in both the SMV and host-rock, lie on a linear regression in 238U/206Pb–207Pb/206Pb–204Pb/206Pb three-dimensional space, indicating a total Pb/U isochron age of 3.15±0.12 Ga (95% confidence level), which is consistent ages determined in previous isotopic studies of NWA 2977 (Sm–Nd age of 3.10±0.05 Ga, Rb–Sr age of 3.29±0.11 Ga, and Pb–Pb baddeleyite age of 3.12±0.01 Ga), and identical to the age of the U–Pb phosphate in a paired meteorite NWA 773, 3.09±0.20 Ga, derived from our dataset. There was no clear difference in the formation age between the phosphates found in the SMV and host-rock, although the shape and size of the grains and the Raman spectra show the evidence of intense shock metamorphism. Based on these findings, the cooling rate of the phosphate was very rapid, constrained to be larger than 140 K/s.

  • Shuji Yamashita, Takafumi Hirata
    2023 Volume 12 Issue 1 Pages A0116
    Published: April 06, 2023
    Released on J-STAGE: April 06, 2023
    Advance online publication: March 08, 2023

    Single particle inductively coupled plasma mass spectrometry combined with the laser ablation technique (LA-spICP-MS) has been used for the determination of particle size and the spatial distribution of metal nanoparticles (MNPs) in various solid samples such as biological samples and semiconductor materials. In this study, we investigated the effect of the fluence of the laser being used on the disintegration of MNPs. Commercially available MNPs of silver and gold (Ag NPs and Au NPs), the sizes of which were determined by transmission electron microscopy (TEM), were analyzed with LA-spICP-MS. We evaluated the degree of disintegration of the original-sized particles, based on a comparison of the size distributions obtained by LA-spICP-MS and other analytical techniques. The disintegration of both the Ag NPs and Au NPs was induced by a laser ablation process when the laser fluence was higher than 1.0 J cm−2, whereas no disintegration was observed when the fluence was lower than 1.0 J cm−2. Moreover, the mean diameter and standard deviation of the determined diameters obtained by LA-spICP-MS were in good agreement with solution-based spICP-MS and TEM analysis within analytical uncertainty. The data obtained here demonstrates that LA-spICP-MS represents a promising potential analytical technique for accurately determining the size of individual MNPs and their spatial distribution in solid samples.

  • Daisuke Takakura, Haruka Yoshida, Shoko Ohashi, Nana Kawasaki
    2023 Volume 12 Issue 1 Pages A0117
    Published: April 11, 2023
    Released on J-STAGE: April 11, 2023
    Advance online publication: March 15, 2023
    Supplementary material

    Aberrant glycosylation of membrane proteins is a hallmark of cancer and a useful molecular marker for the diagnosis of breast cancer (BC). However, the molecular mechanisms by which altered glycosylation affects the malignant transformations associated with BC are poorly understood. Accordingly, we performed comparative membrane N-glycoproteomics using the human BC cell line pair, Hs578T, and its syngeneic normal cell line, Hs578Bst. A total of 359 N-glycoforms derived from 113 proteins were identified in both cell lines, of which 27 were found only in Hs578T cells. Significant changes in N-glycosylation were found in the lysosome-associated membrane protein 1 (LAMP1), the integrin family, and laminin. Confocal immunofluorescence microscopy images revealed the accumulation of lysosomes in the perinuclear space in cancer cells, which could be associated with marked changes in LAMP1 glycosylation, such as a decreased level of polylactosamine chains. Overall, the alterations in glycosylation may be involved in changes in the adhesion and degradation of BC cells.

  • Mark Beattie, Oliver A. H. Jones
    2023 Volume 12 Issue 1 Pages A0118
    Published: April 06, 2023
    Released on J-STAGE: April 06, 2023
    Advance online publication: March 14, 2023
    Supplementary material

    Mass spectrometry is a well-established analytical technique for studying the masses of atoms, molecules, or fragments of molecules. One of the key metrics of mass spectrometers is the limit of detection e.g., the minimum amount of signal from an analyte that can be reliably distinguished from noise. Detection limits have improved greatly over the last 30–40 years to the point that nanogram per litre and even picogram per litre detections are commonly reported. There is however, a difference between detection limits obtained with a single, pure compound in a pure solvent and those obtained from real life samples/matrixes. Determining a practical detection limit for mass spectrometry is difficult because it depends on multiple factors, such as the compound under test, the matrix, data processing methods and spectrometer type. Here we show the improvements in reported limits of detection on mass spectrometers over time using industry and literature data. The limit of detection for glycine and dichlorodiphenyltrichloroethane were taken from multiple published articles spanning a period of 45 years. The limits of detection were plotted against the article’s year of publication to assess whether the trend in improvement in sensitivity resembles Moore’s Law of computing (essentially doubling every two years). The results show that advancements in detection limits in mass spectrometry are close to, but not quite at a rate equivalent to Moore’s Law and the improvements in detection limits reported from industry seem to be greater than those reported in the academic literature.

  • Yamato Miyazaki, Atsushi Yamamoto
    2023 Volume 12 Issue 1 Pages A0119
    Published: April 06, 2023
    Released on J-STAGE: April 06, 2023
    Advance online publication: March 21, 2023

    To evaluate the safety of food for pets, the migration of chemical substances from pet tableware was investigated by mass spectrometry. The presence of polymer additives Irgafos 168 and Erucamide were suspected based on mass spectra and were confirmed to be present in polypropylene tableware. The amount of substances migrated using simulated saliva was examined by liquid chromatography-mass spectrometry after solid phase extraction and purification. Photoionization was found to be suitable for the simultaneous determination of these substances. The detection limits of the established method were 0.019 μg/mL for Irgafos 168 and 0.022 μg/mL for Erucamide. Five different types of pet tableware purchased in local markets were examined and no analytes were detected in the simulated saliva using shaking extraction. In this study, the risk to pets from the substances migrated from pet tableware was considered to be sufficiently low.

  • Ayumi Kubo, Azusa Kubota, Haruki Ishioka, Takuhiro Hizume, Masaaki Ubu ...
    2023 Volume 12 Issue 1 Pages A0120
    Published: April 13, 2023
    Released on J-STAGE: April 13, 2023
    Advance online publication: March 21, 2023
    Supplementary material

    Electron ionization (EI) mass spectrum library searching is usually performed to identify a compound in gas chromatography/mass spectrometry. However, compounds whose EI mass spectra are registered in the library are still limited compared to the popular compound databases. This means that there are compounds that cannot be identified by conventional library searching but also may result in false positives. In this report, we report on the development of a machine learning model, which was trained using chemical formulae and EI mass spectra, that can predict the EI mass spectrum from the chemical structure. It allowed us to create a predicted EI mass spectrum database with predicted EI mass spectra for 100 million compounds in PubChem. We also propose a method for improving library searching time and accuracy that includes an extensive mass spectrum library.

  • Takafumi Hirata, Menghao Yang, Hui Hsin Khoo
    2023 Volume 12 Issue 1 Pages A0121
    Published: May 11, 2023
    Released on J-STAGE: May 11, 2023
    Advance online publication: March 25, 2023

    In situ and rapid analysis of organic compounds using a combination of a newly-developed laser ablation in liquid (LAL) sampling technique combined with electrospray ionisation mass spectrometry (ESI-MS) is reported. The LAL is a technique that allows laser ablation to be conducted in a liquid medium containing organic compounds that were effectively extracted from solid materials into the liquid medium. Three organic compounds (valine, caffeine, and benzyl butyl phthalate (BBP)) were subjected to analysis. The LAL sampling was conducted in the fast-laser scanning mode using Galvanometric optics, and the total ablation time required for the sampling from a 1 mm2 area was about 3 s, thus providing rapid sampling. The resulting sample solution was directly introduced into the ESI-MS system, without the need for any chromatographic separation. To evaluate the analytical capability of the LAL technique coupled with ESI-MS, both the overall transmission efficiencies of analytes from solid materials to the ion detector, and the repeatabilities of the measurements were rigorously tested. This involved the use of synthetic, in-house prepared standard materials containing the analytes. The overall ion yields were about 1.1×10−3% for valine, 8.7×10−3% for caffeine, and 6.7×10−4% for BBP. By comparing the ion yields obtained by the injection of an analyte solution and a standard solution through the mass spectrometer, the recoveries through the LAL sampling were approximately 31% for valine, 45% for caffeine, and 37% for BBP. In addition, the analytical repeatabilities for all analytes were better than 6%. The analytical repeatabilities were mainly affected by either the heterogeneity of the in-house standard materials or changes in the plasma temperature by coexisting, laser-induced sample particles. It should be noted that not only water-soluble compounds (caffeine and valine), but also non-soluble compound (BBP) could be measured by the LAL-ESI-MS, which is one of the great advantages over the conventional liquid extraction surface analysis technique. The data obtained here clearly demonstrate that the LAL-ESI-MS has the potential for being a fast and user-friendly analytical technique for the in-situ detection for both the water-soluble and water-insoluble molecules.

Technical Report
  • Yoshio Takahata, Misato Hara, Kouhei Nishino, Takao Kawakami
    2023 Volume 12 Issue 1 Pages A0122
    Published: May 24, 2023
    Released on J-STAGE: May 24, 2023
    Advance online publication: May 03, 2023
    Supplementary material

    Immuno-mass spectrometry (MS) is a powerful method for the quantitative analysis of low-abundance proteins in biological specimens. In these procedures, collecting specifically and efficiently the target protein antigens from the antigen–antibody complex generated on the surface of nanocarrier beads is crucial and can be performed by hydrolyzing the proteins directly on the beads or after elution. Herein, we optimized the conditions of the immunoaffinity purification via elution using serum α-fetoprotein (AFP) as a model and its specific antibody immobilized covalently on magnetic beads. Antibody-coated beads were incubated with human serum spiked with standard AFP for antigen–antibody reaction. AFP was then eluted from the beads using various eluents, including organic solvents, to optimize the elution conditions. After proteolytically hydrolyzing the eluted protein, stable isotope-labeled standard peptides were added to the hydrolysate to quantify the eluted AFP via liquid chromatography–tandem MS. Using an optimized workflow for quantitative analysis afforded a correlation between the amount of spiked AFP and heavy to light ratios calculated based on peptide ion peak areas, from which an endogenous AFP concentration of 2.3±0.6 ng/mL was determined in normal serum; this is consistent with previous reports using radioimmunoassay methods. The present immuno-MS workflow could apply to the detection and quantitation of other low-abundance biofluid biomarkers.