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The paper explores the applicability of the Kohonen clustering algorithm for peak detection during the preprocessing of mass spectra. Various modifications made to the algorithm's classical version during its implementation in the program code are described . The results of peak detection carried out in four mass spectra of inorganic compounds using the Kohonen algorithm are presented. A brief study is conducted on how the algorithm's output is affected by various parameter values. The Kohonen algorithm and two other approaches are compared in terms of their peak detection quality. The findings suggest that the Kohonen clustering algorithm can be used for the initial detection of mass spectrum peaks; however, certain peculiarities of the algorithm's functioning need to be considered., Author(s): V. V. Lebedev [sup.1] , A. K. Buryak [sup.1] Author Affiliations: (1) grid.465278.a, 0000 0004 0620 3386, Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, , [...]

Adsorbents based on various substrates-silica and a copolymer of styrene with divinylbenzene-are developed for the determination of amino acids by hydrophilic interaction liquid chromatography-mass spectrometry. The optimal version of the structure of the functional layer in two series of the obtained stationary phases was chosen, which provides the best hydrophilization for each substrate. Retention mechanisms were studied and the conditions for the mass-spectrometric detection, separation, and determination of 16 amino acids were chosen. The applicability of the obtained adsorbents and a method for determining amino acids for the analysis of soil extracts were estimated., Author(s): N. Yu. Chikurova [sup.1] , A. V. Gorbovskaia [sup.1] , A. N. Stavrianidi [sup.1] [sup.2] , E. S. Fedorova [sup.2] , A. O. Shemyakina [sup.1] , A. K. Buryak [...]

A comparative study of composites based on imidazolium phosphomolybdates of the SILP type of catalysts for peroxide oxidative desulfurization was performed by mass spectrometry and other physicochemical methods, in particular, XPS (X-ray photoelectron spectroscopy). An analysis of the data obtained revealed partial destruction of heteropolyanions during the synthesis of heterogeneous samples. The results of mass spectrometric measurements are well correlated with the XPS data, indicating the possibility of using mass spectrometry (MS) in the surface-activated laser desorption/ionization (SALDI) technique for characterization of these composites. The results of the analysis of the desulfurization rate showed the important role of the products of partial destruction of heteropolyacid anions in the catalysis of the process. [ABSTRACT FROM AUTHOR]

Rationale: Cluster forms of rhenium sulfides have important practical applications as catalysts in oil refining and thus present high interest. However, only a limited number of rhenium sulfide clusters have been described previously. It is known that cluster formation actively occurs under conditions of laser desorption–ionization; nevertheless, detailed studies of rhenium sulfides under such conditions were apparently not conducted previously. Methods: A sample of natural rhenium sulfide, collected from the fumarolic field of Kudriavy volcano (Iturup island, Russia) in 2002, was investigated using the laser desorption–ionization mass spectrometry method. The formed rhenium sulfide clusters were registered by a time‐of‐flight detector and identified programmatically using the software developed in IPCE RAS. The identification involved a comparison of the distribution of isotopic peak intensities, observed in the resulting mass spectra, with the theoretical probabilities of occurrence of various isotopologues for hypothetical rhenium sulfide species. Results: Over 60 rhenium sulfide clusters of RexSy+ and RexSyOz− types containing up to 10 rhenium atoms were formed when a sample of natural rhenium sulfide was exposed to laser desorption–ionization conditions. Several isolated heterometallic ReXMoSY+ and ReXMoSYOZ− clusters containing up to eight rhenium atoms were additionally observed in the resulting mass spectra. The species with compositions, for which the electrically neutral analogs are known, apparently were the most stable rhenium sulfide clusters among the detected ones. Conclusions: The obtained data allowed summarizing the patterns of formation of rhenium sulfide clusters under conditions of laser desorption‐ionization. The ability of rhenium and sulfur to form cluster species containing from 7 to 10 atoms of rhenium was likely discovered for the first time. The majority of the rhenium sulfide clusters described in this study, notably RexSy+ ions containing over seven atoms of rhenium, were apparently not observed previously. [ABSTRACT FROM AUTHOR]

Rationale: Phosphorotungstic acid (PTA) has many applications, especially in the field of catalysis, due to its structural properties. However, the structure of PTA is studied mainly using theoretical methods. Matrix‐assisted laser desorption/ionization (MALDI) has the potential to be an effective method for the experimental study of heteropolyacids. Limitations of MALDI are the high molecular weight of the particles and the complex distribution of isotopic peak intensities. Both problems can be solved by automatically identifying observed signals by generating hypothetical molecular formulas and estimating their isotopic distributions. Methods: Phosphotungstic acid was studied under conditions of laser desorption/ionization in the absence and in the presence of the matrix. Three types of matrices were used: 2,5‐dihydroxybenzoic acid in water, α‐cyano‐4‐hydroxycinnamic acid in acetonitrile, and sinapic acid (SA) in tetrahydrofuran. Part of the peaks in the resulting mass spectra was identified using in‐house developed software that implements the automated isotopic distribution brute force. Results: The most informative mass spectra were obtained using SA as the matrix, which enabled the detection of particles containing PTA dimers for the first time. The compositions of particles incorporating PTA dimers were determined in an automated manner and can be written as [H3PW12O40]2·2H2O (m/z = 5791.2 Da) and [H3PW12O40]2·4H2O (m/z = 5836.5 Da). Other observed species included (WO3)n·PO3−, HPO2·(WO3)n, and WO2·(WO3)n clusters, with the latter containing W in mixed oxidation states. Conclusions: The combined use of MALDI and an automated identification procedure provided valuable experimental data on the structure and fragmentation of phosphotungstic acid. To the best of our knowledge, this study was the first to report on particles containing phosphotungstic acid dimers. [ABSTRACT FROM AUTHOR]