Analytical Instrument Documents

Imaging mass spectrometry using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-Imaging) has been expanded during the last decade in biological applications, to assess the distribution of proteins, peptides, lipids, drugs, and metabolites in a tissue specimen. In MALDI-Imaging measurements, a laser irradiation point was scanned on a sample surface to acquire a mass spectrum at each point. Analyzing the mass spectra with two-dimensional position information, localization of compounds with inherent molecular weights can be visualized or the mass spectra for certain regions of interests (ROIs) can be created. The JMS-S3000 SpiralTOF (Fig. 1) is a MALDI-TOFMS, which utilizes the JEOL patented spiral ion optical system. It has a 5-10 times longer flight path than the typical reflectron type MALDI-TOFMS. As a result, it can achieve high mass-resolution to separate peaks that have the same nominal mass but have different exact masses (isobaric separation). On the other hand, there are some issues for analyzing high mass resolution and high lateral resolution MALDI-Imaging raw data with common imaging software options such as Biomap.

Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-Imaging MS) is a powerful tool for the biochemical analyses of surfaces. Previously, this technique has been used to determine the spatial distribution of hundreds of unknown compounds in thinly sliced tissue sections. The mass spectral images are generated by changing the laser irradiation point at regular intervals across the sample surface and collecting a mass spectrum for each point. Time-of-flight mass spectrometers (TOFMS) are widely used as the mass analyzer for MALDI-Imaging MS because they are well matched for the MALDI ionization process. However, the fine structure of the matrix crystals and small irregularities in the tissue surface flatness can cause peak drift in the collected mass spectra that is caused by slight differences in the starting point of the flight path for the ions at each laser irradiation point. As a result, the typical reflectron type TOFMS systems have a difficult time achieving high mass resolution from spot to spot over a thinly sliced biological surface. Conversely, the JEOL JMS-S3000 “SpiralTOFTM”, which has 5-10 times longer flight path than the reflectron type TOF, is able to reduce the effect of this mass drift to achieve high mass resolution and high mass accuracy. In this work, we report the advantages of using the SpiralTOF for MALDI-Imaging MS analyses of lipids in a mouse brain tissue section.

Recently, matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) imaging techniques have been developed for biological sciences to evaluate and understand the distribution of various chemicals on biological surfaces. In particular, this technique provides useful visual information about the locations of specific chemicals on surfaces. In this work, we explored the use of MALDI-MS imaging for the forensically applicable sample of gunshot residues (GSR). These measurements were done using a spiral-trajectory ion optics time-of-flight mass spectrometer (SpiralTOF-MS) which has a 17m flight path that provides high resolution capabilities, even down into the lower m/z region. Additionally, the m/z axis remains very stable over the long time period required for MALDI-MS imaging.

Since 1949, the JEOL legacy has been one of outstanding innovation in developing instruments used to advance scientific research and technology. JEOL has over 60 years of expertise in the field of electron microscopy, more than 50 years in mass spectrometry. In this applications note, we performed an analysis of a Gold Star Mothers Postage Stamp by using three JEOL instruments. We used the JSM-IT300LV which the latest addition to JEOL‘s popular series of analytical low vacuum SEM, , the JMS-T100LP “AccuTOF- DART” the first commercially available ambient ionization mass spectrometer, and the JMS-S3000 “SpiralTOF” which has highest mass-resolution and mass accuracy of all commercially available MALDI-TOFMS systems. We can therefore correlate analyses from various analytical techniques on the same sample.

MALDI imaging is a state-of-art mass spectrometry technique that allows for the visualization of chemical distributions on the surfaces of biological and material samples. This analytical technique can provide the chemical distribution on the surface as an image that is mapped using the intensity of the observed ions. The image contains individual MALDI mass spectra at each pixel. Therefore, it is possible to simultaneously carry out high-mass-resolution qualitative analysis and chemical distribution analysis. The JMS-S3000 SpiralTOF (Figure 1) has a unique 17m fl ight path that offers the highest mass resolution and mass accuracy MALDI-TOF MS system. In this work, we demonstrated the MALDI imaging measurement for the fi ngerprints of a smoker and a non-smoker by using the JEOL SpiralTOF system. Additionally, we looked at the smoker’s fi ngerprint using the JEOL JSM-7800F thermal fi eld emission scanning electron microscope (FE-SEM) shown in Figure 2.

Recently, matrix assisted laser desorption/ionization (MALDI) imaging techniques have been developed for biological sciences to evaluate and understand the distribution of various chemicals on biological surfaces. In particular, this technique provides useful visual information about the locations of specific chemicals on surfaces. In this work, we explored the use of laser desorption/ionization (LDI) imaging for forensically applicable samples such as a handwriting sample with a ballpoint ink. These measurements were done using a spiral-trajectory ion optics time-of-flight mass spectrometer (SpiralTOF-MS). This TOF system has a 17m flight path that provides high resolution capabilities even down into the lower m/z region. Additionally, we looked at the SEM/EDS imaging using the JEOL JSM-6510LV scanning electron microscope.

Industrial materials are often evaluated by surface analysis instruments that provide information on surface elements, bonding states, and functional groups. However, there are limited options for surface analysis techniques that provide molecular weight and molecular structure information for organic compounds present on surfaces. Matrix Assisted Laser Desorption Ionization - Time of Flight Mass Spectrometry (MALDI-TOFMS) is a soft ionization technique that can be used to analyze surfaces in order to estimate elemental compositions with accurate mass measurements, obtain structural information by using MS/MS, and map surface compounds by using MS imaging. MALDI-TOFMS uses a high voltage on the target plate to accelerate the ions into the TOFMS analyzer. Therefore, the target plates are conductive and are typically made of stainless steel. MALDI imaging mass spectrometry is widely used for analyzing organic substances on frozen tissue sections. In this case, a frozen tissue section with a thickness of about 10 μm is placed on a conductive glass slide coated with an indium tin oxide (ITO) film. However, for the analysis of industrial products, the target organic compounds are on nonconductive substrates such as resins with millimeter thicknesses. MALDI-TOFMS surface measurements using nonconductive substrates lead to a reduction in mass resolution and a significant decrease in ion intensity due to surface charging. This problem can be solved by pretreating the surface with gold vapor deposition in order to change it from nonconductive to conductive. This method was previously shown to work well in MSTips No. 204 in which the gold vapor deposition method was applied to the MALDI-MS imaging analysis of inks on paper. In this report, we used gold vapor deposition to look at samples on the surface of a 1 mm thick acrylic plate.

Biological markers (biomarkers) are compounds such as terpanes, steranes, and steroids that are derived from organisms present in the original biomass from which organic-rich sediments and oils were formed. These compounds can be measured in both oils and source rock bitumens, and they can be used to establish a correlation between an oil sample and the original petroleum source rock. Combined gas chromatography / mass spectrometry (GC/MS) can be used to analyze for biomarkers in oil samples. However, there are numerous interferences present that have the same integer mass as biomarkers, but different elemental compositions. Because these isobaric compounds have different exact masses than the biomarkers, the interferences can be separated by high-resolution mass spectrometry. Some examples of compounds that interfere with the detection of biomarkers are given in Table I.

Most familiar applications of high resolution mass spectrometry relate to exact mass measurements for elemental composition determination of compounds such as natural products, environmental contaminants, petrochemicals and synthetic organic compounds. However, high resolution can also be useful at the very low end of the mass scale for monitoring gases and isotopes. The GCmate has a mass range that extends as low as m/z 1 and as high as m/z 3000 (at reduced accelerating voltage) and is capable of a resolving power up to 5,000. This is more than sufficient for analyzing low-mass species such as CO and N2 as well as H+, D+, H2+, HD+ etc. The example shown above was obtained by monitoring H2+ (m/z 2.01565) and D+ (m/z 2.0141) from a mixture of D2O and H2O at a resolving power of 3400. The difference in mass between these two species is only 0.00155 u.

A few needles from the holiday tree in the lobby of our Peabody office were extracted with dichloromethane and analyzed with the JEOL GCmate GC/MS system. Components were identified by a library search of the mass spectra. The fragrance comes from a complex mixture of terpenes such as alpha-pinene (familiar pine aroma) and limonene (citrus aroma) and other compounds, such as maltol (fresh-baked bread aroma).


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