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Laser-spark ionization mass spectrometry

  • A versatile ionization scheme for atmospheric pressure MS is presented. It is based on a quasi-continuous laser-induced plasma (LIP), generated by a 26 kHz pulsed DPSS-laser, which is ignited in front of the MS inlet. Analytes are determined with different sampling regimes, comprising either an ambient desorption/ionization mechanism, a liquid-phase or gas-phase sample introduction. The MS signal closely resembles the ionization behavior of APCI-like plasma-based sources, such as DBD or DART. Though LIPs are known to efficiently atomize/ionize any sample material, mass spectra of intact molecular ions are recorded, exhibiting low fragment-ion content. To understand this contradictory behavior, the plasma properties are investigated that lead to the formation of molecular ions. Comprehensive studies include optical emission spectroscopy, shadowgraph imaging and mass spectrometry diagnostics. The results show that the ionization of analyte does not occur in the plasma itself, butA versatile ionization scheme for atmospheric pressure MS is presented. It is based on a quasi-continuous laser-induced plasma (LIP), generated by a 26 kHz pulsed DPSS-laser, which is ignited in front of the MS inlet. Analytes are determined with different sampling regimes, comprising either an ambient desorption/ionization mechanism, a liquid-phase or gas-phase sample introduction. The MS signal closely resembles the ionization behavior of APCI-like plasma-based sources, such as DBD or DART. Though LIPs are known to efficiently atomize/ionize any sample material, mass spectra of intact molecular ions are recorded, exhibiting low fragment-ion content. To understand this contradictory behavior, the plasma properties are investigated that lead to the formation of molecular ions. Comprehensive studies include optical emission spectroscopy, shadowgraph imaging and mass spectrometry diagnostics. The results show that the ionization of analyte does not occur in the plasma itself, but in the cold adjacent gas layer. The pulsed character of LIPs induces an expanding shockwave, which concentrically expands around the plasma core and sweeps the molecules toward the plasma edges, where they are ionized either directly by the self-emission of the hot core or via interaction with secondary reactants. However, this unidirectional transport causes a rarefaction inside the plasma center, which leads to a decrease in plasma intensity and number density. Thus, a restoration of the former gaseous medium by other dynamically equilibrated diffusion processes would be favorable. Besides gas replenishing, we demonstrate the beneficial use of an acoustical standing wave inside an ultrasonic resonator on the performance of the LIP.zeige mehrzeige weniger

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  • EMSC 2018 Saarbruecken.pdf
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Metadaten
Autor*innen:Andreas Bierstedt
Koautor*innen:Sebastian van Wasen, Jens Riedel
Dokumenttyp:Vortrag
Veröffentlichungsform:Präsentation
Sprache:Englisch
Jahr der Erstveröffentlichung:2018
Organisationseinheit der BAM:1 Analytische Chemie; Referenzmaterialien
1 Analytische Chemie; Referenzmaterialien / 1.3 Instrumentelle Analytik
1 Analytische Chemie; Referenzmaterialien / 1.9 Chemische und optische Sensorik
MP Mitglied des Präsidiums
MP Mitglied des Präsidiums / PST Präsidiale Stabsstelle
DDC-Klassifikation:Naturwissenschaften und Mathematik / Chemie / Analytische Chemie
Freie Schlagwörter:Ambient mass spectrometry; DPSS laser; Laser-induced plasma; Laser-spark ionization
Themenfelder/Aktivitätsfelder der BAM:Umwelt
Umwelt / Sensorik
Veranstaltung:European Mass Spectrometry Conference 2018
Veranstaltungsort:Saarbrücken, Germany
Beginndatum der Veranstaltung:11.03.2018
Enddatum der Veranstaltung:15.03.2018
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:19.03.2018
Referierte Publikation:Nein
Eingeladener Vortrag:Nein
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