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13. New Perspectives on the 143Nd/144Nd Palaeoceanographic Tracer on Foraminifera: The State‐of‐the‐Art Frontiers of Analytical Methods.

Author

Scheiner, Filip, Ackerman, Lukáš, Holcová, Katarína, Rejšek, Jan, Vollstaedt, Hauke, Ďurišová, Jana, and Santolík, Václav

Subjects
FORAMINIFERA, WATER masses, ISOTOPIC analysis, ELECTROSPRAY ionization mass spectrometry, MASS spectrometry, STANDARD deviations
Abstract

The 143Nd/144Nd isotopic composition of foraminifera represents one of the most prominent palaeoceanographic proxies enabling tracing of particular water masses due to the short residence time of Nd in seawater and large‐scale provinciality resulting from its lithogenic origin. Despite its wide use, the applicability of foraminiferal Nd isotopic systematics as a palaeoceanographic tracer is largely hampered by the amount of material needed for precise analyses. Here, we analyzed for the first time foraminiferal samples of a combined weight of only ∼300–500 μg (ca. 300 pg to 1 ng Nd loaded). We followed a methodology that utilizes Nd separation from the matrix and provides precise 143Nd/144Nd determinations by thermal ionization mass spectrometry with sensitive 1013 Ω amplifiers. Two different techniques analyzing NdO+ and Nd+ (single/double filament configurations) were employed and tested to assess the limits both in terms of in‐run precision and accuracy concluding that the former method yielded an external reproducibility on the determined 143Nd/144Nd better than ∼90 ppm (2RSD; relative standard deviation) for 100 pg Nd loads. The overall veracity was tested by multiple analyses of Holocene and Miocene foraminifera from the Mediterranean region. Pooled data were obtained in agreement with previous studies attesting that multiple analyses of even very low Nd loads (≤1 ng) can lead to sufficient precision. As revealed by our newly obtained data, individual foraminiferal species show a significant naturally induced 143Nd/144Nd variability that needs to be considered when pursuing Nd isotopic analysis. Key Points: 143Nd/144Nd isotopic composition of foraminifera of a combined weight of ∼300–500 µgThermal ionization mass spectrometry with sensitive 1013 Ω amplifiersTwo different techniques analyzing NdO+ and Nd+ (single/double filament) [ABSTRACT FROM AUTHOR]

Published
2022
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14. Development and applications of ambient mass spectrometry techniques

Author

Rejšek, Jan, Cvačka, Josef, Lemr, Karel, and Klejdus, Bořivoj

Subjects
desorpční fotoionizace, hmotnostně-spektrometrické zobrazování, desorpční elektrosprej, desorption photoionization, mass spectrometry imaging, desorption electrospray
Abstract

(EN) Ambient mass spectrometry defines the versatile group of methods providing analysis of solid sample surfaces and liquids in an open atmospheric pressure environment, where the sample is simultaneously accessible to another treatment. Ambient mass spectrometry is a sharply developing research area in the analytical chemistry. It provides fast, direct analysis of objects without any sample pretreatment with the use of the mass spectrometer. Desorption electrospray ionization (DESI) and desorption atmospheric pressure photoionization (DAPPI) equipped with software control of the sample holder were investigated in this doctoral thesis. These methods use a spray of solvents for desorption and ionization molecules from solid substrate and they are suitable tools for mass spectrometry imaging (MSI) of low molecular organic compounds, where the chemical identity of molecules present on a surface is examined as a function of spatial distribution. This project deals with applications and instrumental development. As for the applications, the position of the defense glands on insect bodies, separation of the lipids in complex mixtures on thin-layer chromatography (TLC) plates, or steroid metabolites in woman urine during pregnancy were thus investigated. As for the instrumental development, the most...

Published
2018

15. Ion Source with Laser Triangulation for Ambient Mass Spectrometry of Nonplanar Samples

Author

Rejšek, Jan, Vrkoslav, Vladimír, Pokorný, Vít, Přibyl, Vladimír, and Cvačka, Josef

Abstract

The analysis of nonplanar samples in ambient mass spectrometry poses a formidable challenge. Here, an ion source equipped with laser triangulation for analyzing nonplanar surfaces was constructed. It was designed as a two-position device, where the sample height was measured using laser triangulation and the target compounds were then analyzed. Thanks to a stage movable in xyz, the ion source maintained an optimal vertical distance between the sample and the sampling capillary for each measured spot during the surface analysis. The xyz-coordinates for the movement of the sample stage were computed using the laser sensor data in such a way as to avoid direct contact of the sampling capillary and the measured surface. The ion source performance and its ability to analyze various morphologies were tested using desorption electrospray ionization with plastic objects coated by 2,5-dimethoxybenzoic acid. The experiments showed excellent performance for nonplanar samples but also revealed some limitations especially on object edges and steep slopes. The applicability of the ion source operated in desorption electrospray ionization and desorption atmospheric pressure photoionization was examined for food and pharmaceutical samples. Chemicals on the surface of nonplanar samples were probed along a line extending across the surface of the measured objects. The device provided high-quality spectra, regardless of the sample height at the measured spot. The automatic adjustments of the sample stage in xyzproved to be beneficial for analyzing nonplanar samples and for simultaneous measurement of samples with various dimensions and shapes.

Published
2024
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18. The use of ambient ionization techniques in mass spectrometry

Author

Rejšek, Jan, Cvačka, Josef, and Coufal, Pavel

Subjects
ambientní ionizace, tenkovrstvá chromatografie, thin-layer chromatography, DAPPI, DESI, mass spectrometry, ambient ionization, hmotnostní spektrometrie
Abstract

Keywords: ambient ionization techniques; mass spectrometry; desorption electrospray ionization; desorption atmospheric pressure photoionization; thin layer chromatography; lipids, mass spectrometry imaging Ambient ionization technique in mass spectrometry is an ionization, which carries out in open space outside the machine and which does not require any, or only a minimal sample pretreatment. DESI (desorption electrospray ionization) and DAPPI (desorption atmospheric pressure photoionization) equipped with software control of the spray emitter position for analysis of low molecular organic compounds were investigated in this thesis. These methods use a spray of solvents for desorption and ionization molecules from solid substrate. Conditions for the successful analysis of phospholipids, wax esters and some other compounds were developed. Ambient ionization techniques were quantitatively compared. The application was HPTLC/DESI-MS of lipid's mixture and HPTLC/DAPPI-MS of vernix caseosa. DAPPI-MS was applied for the analysis of termites of Prorhinotermes genus (Isoptera, Rhinotermitidae). Pilot experiments of two dimensional analysis and mass spectrometry imaging were realized.

Published
2013

19. Preparation of asymmetrically substituted diphenylacetylenes usable in molecular electronics

Author

Rejšek, Jan, Jindřich, Jindřich, and Veselý, Jan

Abstract

Preparation of asymetrically substituted diphenylacetylenes usable in molecular electronics Abstract This bachelor's work deals with synthesis of assymetrically substituted diphenylacetylenes and their transformation into (η4 -cyclobutadiene)-(η5 - cyclopentadienyl)cobalt complexes, which should be used and researched as molecular rotors. Multistep synthesis concerning conversion of primary arylamines into tertiary by N-permethylation, nucleophilic acyl substitution and Sonogashira coupling was prepared asymmetrically substituted diphenylacetylene with, which consequently underwent cycloaddition [2 + 2] with cyclopentadienyldicarbonylcobalt. Creating (η4 -cyclobutadiene)-(η5 -cyclopentadienyl)cobalt complexe was identified by MS. Keywords: diphenylacetylene, Sonogashira coupling, (η4 -cyclobutadiene)- (η5 -cyclopentadienyl)cobalt complex, cycloaddition [2 + 2], molecular rotor

Published
2010

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