For the development and optimization of materials processing a collection of thermodynamic information concerning substances that participate in the reactions is important. One fundamental way to obtain such information is to measure the vapor pressure of gas species under conditions where they are in equilibrium with the condensed phases. Over the past 60 years Knudsen cell mass spectrometry has been used to identify and quantitatively determine gas species at high temperatures. This article describes thermodynamic foundation and examples of measurements in order to demonstrate the use of mass spectrometry focusing on the field of process metallurgy and recycling processes.
Presolar grains are stardust that condensed in stellar outflows or stellar ejecta, and was incorporated in meteorites. They remain mostly intact throughout the journey from stars to the earth, keeping information of their birthplaces. Studies of presolar grains, which started in 1987, have produced a wealth of information about nucleosynthesis in stars, mixing in stellar ejecta, and temporal variations of isotopic and elemental abundances in the Galaxy. Recent instrumental advancements in secondary ion mass spectrometry (SIMS) brought about the identification of presolar silicate grains. Isotopic and mineralogical investigations of sub-μm grains have been performed using a combination of SIMS, transmission electron microscopy (TEM) and focused ion beam (FIB) techniques. Two instruments have been developed to study even smaller grains (∼50 nm) and measure isotopes and elements of lower abundances than those in previous studies.
Metabolome, a total profile of whole metabolites, is placed on downstream of proteome. Metabolome is thought to be results of implementation of genomic information. In other words, metabolome can be called as high resolution phenotype. The easiest operation of metabolomics is the integration to the upstream ome information including transcriptome and/or proteome. Those trials have been reported at a certain scientific level. In addition, metabolomics can be operated in stand-alone mode without any other ome information. Among metabolomics tactics, the author’s group is particularly focusing on metabolic fingerprinting, in which metabolome information is employed as explanatory variant to evaluate response variant. Metabolic fingerprinting technique is expected not only for analyzing slight difference depending on genotype difference but also for expressing dynamic variation of living organisms. The author introduces several good examples which he performed. Those are useful for easy understanding of the power of metabolomics. In addition, the author mentions the latest technology for analysis of metabolic dynamism. The author’s group developed a facile analytical method for semi-quantitative metabolic dynamism. The author introduces the novel method that uses time dependent variation of isotope distribution based on stable isotope dilution.
The techniques and measurement methods developed in the Environmental Survey and Monitoring of Chemicals by Japan’s Ministry of the Environment, as well as a large amount of knowledge archived in the survey, have led to the advancement of environmental analysis. Recently, technologies such as non-target liquid chromatography/high resolution mass spectrometry and liquid chromatography with micro bore column have further developed the field. Here, the general strategy of a method developed for the liquid chromatography/mass spectrometry (LC/MS) analysis of environmental chemicals with a brief description is presented. Also, a non-target analysis for the identification of environmental pollutants using a provisional fragment database and “MsMsFilter,” an elemental composition elucidation tool, is presented. This analytical method is shown to be highly effective in the identification of a model chemical, the pesticide Bendiocarb. Our improved micro-liquid chromatography injection system showed substantially enhanced sensitivity to perfluoroalkyl substances, with peak areas 32–71 times larger than those observed in conventional LC/MS.
Imaging mass spectrometry (IMS) is a toolbox of versatile techniques that enable us to investigate analytes in samples at molecular level. In recent years, IMS, and especially matrix-assisted laser desorption/ionisation (MALDI), has been used to visualise a wide range of metabolites in biological samples. Simultaneous visualisation of the spatial distribution of metabolites in a single sample with little tissue disruption can be considered as one important advantage of MALDI over other techniques. However, several technical hurdles including low concentrations and rapid degradation rates of small molecule metabolites, matrix interference of signals and poor ionisation, need to be addressed before MALDI can be considered as a reliable tool for the analysis of metabolites such as neurotransmitters in brain tissues from different sources including humans. In the present review we will briefly describe current MALDI IMS techniques used to study neurotransmitters and discuss their current status, challenges, as well as future prospects.
The end groups in radically polymerized poly(methyl methacrylate) samples with tert-butyl peroxy-2-ethylhexanoate as an aliphatic peroxide initiator and 1-octanethiol as a chain transfer reagent were complementarily characterized by high-resolution matrix assisted laser desorption/ionization (MALDI) spiral time-of-flight mass spectrometry (MS) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The end groups comprised of three types of the initiator fragments and octylthio group originating from the chain transfer agent were confirmed by MALDI-MS measurements. In addition, their quantitative information was obtained by Py-GC-MS. Furthermore, combined with size exclusion chromatographic fractionation, the molar mass dependence of the end groups in the PMMA samples was also examined. It was suggested that the relative content of the octylthio end groups might increase with increase in the molar mass of the fractions. The observed results were interpreted in terms of the polymerization reactions of the PMMA samples.
Stable cluster sizes and compositions have been investigated for cations and anions of ionic bond clusters such as alkali halides and transition metal oxides by ion mobility-mass spectrometry (IM-MS). Usually structural information of ions can be obtained from collision cross sections determined in IM-MS. In addition, we have found that stable ion sizes or compositions were predominantly produced in a total ion mass spectrum, which was constructed from the IM-MS measurement. These stable species were produced as a result of collision induced dissociations of the ions in a drift cell. We have confirmed this result in the sodium fluoride cluster ions, in which cuboid magic number cluster ions were predominantly observed. Next the stable compositions, which were obtained for the oxide systems of the first row transition metals, Ti, Fe, and Co, are characteristic for each of the metal oxide cluster ions.
Serum and plasma contain thousands of different proteins and peptides, which can provide valuable information about the numerous processes that take place within the body. However, detailed analysis of proteins and peptides in serum and plasma remains challenging due to the presence of many high-abundance proteins, the large dynamic range of protein and peptide concentrations, the extensive complexity caused by posttranslational modifications, and considerable individual variability. In particular, detailed analysis and identification of native peptides is extremely difficult due to the tremendous variety of cleavage possibilities and posttranslational modifications, which results in extremely high complexity. Therefore, widely ranging searches based on peptide identification are difficult. Herein, we describe the highly accurate and sensitive quantitative analysis of over 2,500 peptides with the concentration limit of about 10 pM. The strategy combined isobaric tag labeling, amine-reactive 6-plex tandem mass tag labeling, and a modified differential solubilization method for high-yield peptide extraction [Saito, T. et al. J. Electrophoresis 2013 57: 1–9]. Using this strategy, we quantitatively analyzed six pooled plasma samples (three pre-surgery and three post-surgery) to discover potential candidate biomarker peptides of renal cell carcinoma. The concentrations of 27 peptides were found to be altered following surgery. A preliminary validation study was conducted using about 80 plasma samples to demonstrate the possibility that even unidentified potential candidate biomarker peptides can be verified using the isotope tag/dimethyl labeling method. We also discuss technical consideration and potential of this strategy for facilitating native peptide research.
Sph, S1P, and Cer, derived from the membrane sphingolipids, act as intracellular and intercellular mediators, involved in various (path) physiological functions. Accordingly, determining the distributions and concentrations of these sphingolipid mediators in body tissues is an important task. Consequently, a method for determination of sphingolipids in small quantities of tissue is required. Sphingolipids analysis has been dependent on improvements in mass spectrometry (MS) technology. Additionally, decomposition of sphingosine-1-phosphate (S1P) in the tissue samples before preparation for MS has hindered analysis. In the present study, a method for stabilization of liver samples before MS preparation was developed using a heat stabilizer (Stabilizor™ T1). Then, a LC-MS/MS method using a triple-quadrupole mass spectrometer with a C8 column was developed for simultaneous determination of sphingolipids in small quantities of liver specimens. This method showed good separation and validation results. Separation was performed with a gradient elution of solvent A (5 mmol L−1 ammonium formate in water, pH 4.0) and solvent B (5 mmol L−1 ammonium formate in 95% acetonitrile, pH 4.0) at 300 μL min−1. The lower limit of quantification was less than 132 pmol L−1, and this method was accurate (∼13.5%) and precise (∼7.13%) for S1P analysis. The method can be used to show the tissue distribution of sphingolipids.
Ambient ionization mass spectrometry is one of the most challenging analytical tools in the field of biomedical research. We previously demonstrated that probe electrospray ionization mass spectrometry (PESI-MS) could potentially be used in the rapid diagnosis of cancer. Although this technique does not require a tedious sample pretreatment process, it was not possible for our previously reported setup to be applied to cases involving the direct sampling of tissues from living animal and large animal subjects, because there would not be enough room to accommodate the larger bodies juxtaposed to the ion inlet. To make PESI-MS more applicable for the real-time analysis of living animals, a long auxiliary ion sampling tube has been connected to the ion inlet of the mass spectrometer to allow for the collection of ions and charged droplets from the PESI source (hereafter, referred to as non-proximate PESI). Furthermore, an additional ion sampling tube was connected to a small diaphragm pump to increase the uptake rate of air carrying the ions and charged droplets to the ion inlet. This modification allows for the extended ion sampling orifice to be positioned closer to the specimens, even when they are too large to be placed inside the ionization chamber. In this study, we have demonstrated the use of non-proximate PESI-MS for the real-time analysis for biological molecules and pharmacokinetic parameters from living animals.
We report the application of tapping-mode scanning probe electrospray ionization (t-SPESI) to mass spectrometry imaging of industrial materials. The t-SPESI parameters including tapping solvent composition, solvent flow rate, number of tapping at each spot, and step-size were optimized using a quadrupole mass spectrometer to improve mass spectrometry (MS) imaging of thin-layer chromatography (TLC) and additives in polymer films. Spatial resolution of approximately 100 μm was achieved by t-SPESI imaging mass spectrometry using a fused-silica capillary (50 μm i.d., 150 μm o.d.) with the flow rate set at 0.2 μL/min. This allowed us to obtain discriminable MS imaging profiles of three dyes separated by TLC and the additive stripe pattern of a PMMA model film depleted by UV irradiation.
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