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Subject: Mass spectrometry × WGL Institute: IFWD ×

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Now showing 1 - 3 of 3
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    The use of matrix-specific calibrations for oxygen in analytical glow discharge spectrometry
    (Dordrecht : Springer, 2014) Gonzalez-Gago, C.; Smid, P.; Hofmann, T.; Venzago, C.; Hoffmann, V.; Gruner, W.
    The performance of glow discharge optical emission spectroscopy and mass spectrometry for oxygen determination is investigated using a set of new conductive samples containing oxygen in the percent range in three different matrices (Al, Mg, and Cu) prepared by a sintering process. The sputtering rate corrected calibrations obtained at standard conditions for the 4 mm anode (700 V, 20 mA) in GD-OES are matrix independent for Mg and Al but not for Cu. The importance of a "blue shifted" line of oxygen at 130.22 nm (first reported by Köster) for quantitative analyses by GD-OES is confirmed. Matrix-specific calibrations for oxygen in GD-MS are presented. Two source concepts - fast flow (ELEMENT GD) and low gas flow (VG9000) - are evaluated obtaining higher sensitivity with the static flow source. Additional experiments using Ar-He mixtures or μs pulsed GD are carried out in ELEMENT GD aiming to improve the oxygen sensitivity.
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    Electron-transfer initiated nucleophilic substitution of thiophenolate anion by 1-chloro-substituted 4-(thiazol-2-ylazo)naphthalenes
    (Amsterdam : Elsevier B.V., 2020) Dmitrieva, E.; Yu, X.; Hartmann, H.
    In this work, the electrochemical transformation of 5-chloro-2-[(4-chloronaphthalen-1-yl)azo]thiazoles (A) into the corresponding radical anion A·− and its subsequent reaction with diphenyldisulfide (PhSSPh) was studied. It was found that the primarily generated azo anion radical A·− is able to initiate an electron transfer process which converts the disulfide into its thiolate anion PhS−. This anion was subsequently able to substitute the Cl- and H-groups by phenylmercapto moieties in the starting azo compound A. The structures of the phenylmercapto-substituted azo compounds thus generated were confirmed by thin-layer chromatography and mass spectrometry using independently prepared compounds as references.
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    Surface acoustic wave nebulization improves compound selectivity of low-temperature plasma ionization for mass spectrometry
    (London : Nature Publishing Group, 2021) Kiontke, Andreas; Roudini, Mehrzad; Billig, Susan; Fakhfouri, Armaghan; Winkler, Andreas; Birkemeyer, Claudia
    Mass spectrometry coupled to low-temperature plasma ionization (LTPI) allows for immediate and easy analysis of compounds from the surface of a sample at ambient conditions. The efficiency of this process, however, strongly depends on the successful desorption of the analyte from the surface to the gas phase. Whilst conventional sample heating can improve analyte desorption, heating is not desirable with respect to the stability of thermally labile analytes. In this study using aromatic amines as model compounds, we demonstrate that (1) surface acoustic wave nebulization (SAWN) can significantly improve compound desorption for LTPI without heating the sample. Furthermore, (2) SAWN-assisted LTPI shows a response enhancement up to a factor of 8 for polar compounds such as aminophenols and phenylenediamines suggesting a paradigm shift in the ionization mechanism. Additional assets of the new technique demonstrated here are (3) a reduced analyte selectivity (the interquartile range of the response decreased by a factor of 7)—a significant benefit in non-targeted analysis of complex samples—and (4) the possibility for automated online monitoring using an autosampler. Finally, (5) the small size of the microfluidic SAWN-chip enables the implementation of the method into miniaturized, mobile LTPI probes.