TY - JOUR A1 - Bierstedt, Andreas A1 - Riedel, Jens T1 - High-repetition rate laser ablation coupled to dielectric barrier discharge postionization for ambient mass spectrometry N2 - Most ambient sample introduction and ionization techniques for native mass spectrometry are highly selective for polar agents. To achieve a more general sensitivity for a wider range of target analytes, a novel laser ablation dielectric barrier discharge (LA DBD) ionization scheme was developed. The Approach employs a two-step mechanism with subsequent sample desorption and post-ionization. Effective Ablation was achieved by the second harmonic output (λ = 532 nm) of a diode pumped Nd:YVO₄ laser operating at a high-repetition rate of several kHz and pulse energies below 100 μJ. The ejected analytecontaining aerosol was consecutively vaporized and ionized in the afterglow of a DBD plasma jet. Depending on their proton affinity the superexcited Helium species in this afterglow produced analyte ions as protonated and ammoniated species, as well as radical cations. The optimization procedure could corroborate underlying conceptual consideration on the ablation, desorption and ionization mechanisms. A successful detection of a variety of target molecules could be shown from the pharmaceutical ibuprofen, urea, the amino acids L-arginine, L-lysine, the polymer polyethylene glycol, the organometallic compound ferrocene and the technical mixture wild mint oil. For a reliable evaluation of the introduced detection procedure spectra from the naturally abundant alkaloid capsaicin in dried capsicum fruits were recorded. KW - Laser ablation KW - High-repetition rate laser KW - Dielectric barrier discharge KW - Ambient mass spectrometry PY - 2016 U6 - https://doi.org/10.1016/j.ymeth.2016.02.002 SN - 1046-2023 IS - 104 SP - 3 EP - 10 PB - Elsevier CY - Oxford AN - OPUS4-36730 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bierstedt, Andreas A1 - Bräkling, S. A1 - Rieger, J. A1 - Kersten, H. A1 - Glaus, Reto A1 - Gornushkin, Igor B. A1 - Riedel, Jens T1 - Development and characterization of an airborne laser-spark ion source for ambient desorption / ionization mass spectrometry N2 - A novel direct sampling ionization scheme for ambient mass spectrometry is presented. Desorption and ionization is achieved by a quasi-continuous laser induced plasma in air. Since there are no solid or liquid electrodes involved the ion source does not suffer from chemical interferences or fatigue originating from erosive burning or from electrode consumption. A laser plasma was ignited under ambient conditions in front of a modified TOF MS atmospheric pressure interface, using a high repetition rate DPSS laser operating at 532 nm and 26 kHz and an aspherical lens with a focal length of 8 mm. Emission spectroscopy (40-1100 nm) and time resolved studies on specific plasma parameters revealed insight into the physical and chemical plasma properties. Plasma ignition can be performed in rare gases and under ambient conditions. The hot plasma zone was kept at a certain distance from the sample region. Thus, effective collisional cooling seemed to prevent thermal fragmentation. Every single spark generates a shockwave, providing new reactive species, which expands concentrically from the hot region. Under ambient conditions primary charge carriers (ions and electrons) as well as VUV radiation initialize reaction cascades equivalent to other ambient ionization methods, such as DART or DBD. Mass spectra of polar/nonpolar hydrocarbons, sugars, pharmaceuticals and natural biomolecules in food were observed. Comprehensive emission spectroscopic measurements and time resolved electron current studies revealed insight into some plasma properties, such as the emitted high energetic radiation and the time evolution of the expanding plume. T2 - International Mass Spectrometry Conference 2016 CY - Toronto, ON, Canada DA - 20.08.2016 KW - laser-spark KW - laser-induced plasma KW - ambient mass spectrometry KW - emission spectroscopy PY - 2016 AN - OPUS4-37281 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bierstedt, Andreas A1 - Riedel, Jens T1 - Airborne laser-spark for ambient desorption/ionisation N2 - A novel direct sampling ionisation scheme for ambient mass spectrometry is presented. Desorption and ionisation are achieved by a quasi-continuous laser induced plasma in air. Since there are no solid or liquid electrodes involved the ion source does not suffer from chemical interferences or fatigue originating from erosive burning or from electrode consumption. The overall plasma maintains electro-neutrality, minimising charge effects and accompanying long term drift of the charged particles trajectories. In the airborne plasma approach the ambient air not only serves as the plasma medium but at the same time also slows down the nascent ions via collisional cooling. Ionisation of the analyte molecules does not occur in the plasma itself but is induced by interaction with nascent ionic fragments, electrons and/or far ultraviolet photons in the plasma vicinity. At each individual air-spark an audible shockwave is formed, providing new reactive species, which expands concentrically and, thus, prevents direct contact of the analyte with the hot region inside the plasma itself. As a consequence the interaction volume between plasma and analyte does not exceed the threshold temperature for thermal dissociation or fragmentation. Experimentally this indirect ionisation scheme is demonstrated to be widely unspecific to the chemical nature of the analyte and to hardly result in any fragmentation of the studied molecules. A vast ensemble of different test analytes including polar and non-polar hydrocarbons, sugars, low mass active ingredients of pharmaceuticals as well as natural biomolecules in food samples directly out of their complex matrices could be shown to yield easily accessible yet meaningful spectra. Since the plasma medium is humid air, the chemical reaction mechanism of the ionisation is likely to be similar to other ambient ionisation techniques. N2 - Wir stellen hier eine neue Ionisationsmethode für die Umgebungsionisation (ambient ionisation) vor. Sowohl die Desorption als auch die Ionisation erfolgen hierbei durch ein laserbetriebenes Luftplasma. Die Abwesenheit fester oder flüssiger Elektroden hat zur Folge, dass die Methode weder unter chemischen Interferenzen noch unter Verschleiß durch Korrosionsbrand oder abgetragenes Elektrodenmaterial leidet. Insgesamt betrachtet herrscht in dem Plasma Elektroneutralität, wodurch Aufladungseffekte minimiert werden, die andernfalls zu einer langfristigenÄderung der Flugbahnen von Ionen während der Experimente führen kann. In dem Ansatz eine freischwebende Luftentladung bei Atmosphärendruck zu verwenden agiert die Luft nicht nur als Plasmamedium sondert dient zusätzlich als Badgas für die stoßinduzierte Kühlung der entstehenden Ionen. Die Ionisierung der Analytmoleküle erfolgt nicht unmittelbar im Plasma sondern in dessen direkter Umgebung durch Wechselwirkung mit freigesetzten ionischen Luftspezies, freien Elektronen oder Photonen im kurzwelligen ultravioletten Bereich. Jede Laserentladung erzeugt eine hörbare Stoßwelle, in welcher neu produzierte reaktive Spezies freigesetzt werden, welche sich konzentrisch ausbreiten, so dass eine Diffusion der Analytmoleküle ins heiße Innere des Plasmas verhindert wird. Daraus folgt, dass im Interaktionsvolumen zwischen Plasma und Analyt der Temperaturgrenzwert für eine thermische Dissoziation oder Fragmentierung der Moleküle nicht überschritten wird. Experimentell konnte belegt werden, dass das vorgestellte Ionisierungsschema sehr unselektiv bezüglich der chemischen Analytklasse ist und kaum Fragmentierungsprodukte beobachtet werden können. Messungen einer breitgefächerten Auswahl unterschiedlicher Testsubstanzen, wie beispielsweise polarer und unpolarer Kohlenwasserstoffe, Zuckern, niedermolekularer pharmazeutischer Wirkstoffe, sowie natürlicher Biomoleküle in Lebensmittelproben unmittelbar aus ihren komplexen Matrizes, führten zu aussagekräftigen Massenspektren. Zumal das Lasermedium feuchte Luft ist, scheint der Reaktionsmechanismus dem anderer Atmosphärendruckionisierungsmethoden zuähneln. KW - Laser-spark KW - Laser-induced plasma KW - DPSS laser KW - High repetition rate KW - Ambient mass spectrometry KW - Time-of-flight mass spectrometry KW - Ionisation PY - 2016 U6 - https://doi.org/10.1255/ejms.1417 SN - 1469-0667 VL - 22 IS - 3 SP - 105 EP - 114 PB - IM Publications LLP CY - Chichester, UK AN - OPUS4-37286 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bierstedt, Andreas A1 - Riedel, Jens T1 - Combination of Raman spectroscopy and laser ablation mass spectrometry T2 - Doktorandenseminar des DAAS -Spektroskopie und Spurenanalytik 2014 CY - Münster, Germany DA - 2014-09-22 PY - 2014 AN - OPUS4-33641 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bierstedt, Andreas A1 - Kersten, H. A1 - Glaus, Reto A1 - Gornushkin, Igor B. A1 - Riedel, Jens T1 - Development of a laser induced plasma ion source coupled to ambient mass spectrometry N2 - Only a few years after the invention of the laser, the concept of laser microprobe mass spectrometry (LMMS), a technique which employed intense laser radiation for ion generation, was introduced. In these early studies at excessive irradiation microplasma formation could be observed to be an effective channel for ion formation. However, this plasma generation in vacuum led to undesired distortions of the mass analyzers and, thus, was discarded as an analytical ion source. Under ambient conditions, the surrounding air effectively cools the plasma cloud, making the plasma more controllable. The resulting laser induced plasma is nowadays commonly used in laser induced breakdown spectroscopy (LIBS) applications as excitation source for optical emission spectroscopy experiments. However, little effort has been made to introduce a LIBS plasma as a promising ion source for ambient mass spectrometry. The main hindrance is the transient character of laser induced plasmas that typically only has a lifetime on the order of several microseconds. This drastically reduces the duty cycle of these plasma sources. After these microseconds, the generated ions recombinate to uncharged atoms and even newly bound molecules, making them inaccessible to mass-to-charge analyzers. The advent of high repetition lasers together with the ever growing knowledge about manipulation of charged species at atmospheric pressures allow overcoming these obstacles. This presentation will introduce an ionization scheme using a laser induced plasma as the primary ion source. We believe that this novel ionization strategy will pave the way for future applications in ambient mass spectrometry. T2 - 5. Berliner Chemie Symposium CY - Berlin, Germany DA - 12.04.2016 KW - Laser induced plasma KW - Time-of-flight mass spectrometry KW - Ambient mass spectrometry KW - Ionization KW - Laser induziertes Plasma KW - Flugzeitmassenspektrometer KW - Atmosphärendruckmassenspektrometrie KW - Ionisierung PY - 2016 AN - OPUS4-35732 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bierstedt, Andreas A1 - Kersten, H. A1 - Glaus, Reto A1 - Gornushkin, Igor B. A1 - Riedel, Jens T1 - Laser induced plasma ion source for ambient mass spectrometry N2 - Laser microprobe mass analysis (LMMS) employs local ionization by a focused laser and subsequent mass analysis. At excessive irradiation microplasmas led to undesired distortions. Thus, LMMS was discarded as promising ion source. Effective cooling under ambient conditions resulted in more controllable plasmas and development of laser induced breakdown spectroscopy (LIBS). However, little effort has been made to combine LIBS and ambient MS, since these plasmas only provide microsecond lifetimes. After these, recombination yields uncharged and newly bound species, making them inaccessible for MS. The combination of high repetition rate lasers together with growing knowledge about manipulation of charged species at atmospheric pressure allow overcoming these obstacles. T2 - 49. Jahrestagung der Deutschen Gesellschaft für Massenspektrometrie (DGMS) CY - Hamburg, Germany DA - 28.02.2016 KW - laser induced plasma KW - ion source KW - ambient mass spectrometry KW - emission spectroscopy KW - laser induziertes Plasma KW - Ionenquelle KW - Atmosphärendruck-Massenspektrometrie KW - Emissionsspektroskopie PY - 2016 AN - OPUS4-35454 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bierstedt, Andreas A1 - Warschat, Carsten A1 - Michalik-Onichimowska, Aleksandra A1 - Riedel, Jens A1 - Rurack, Knut T1 - Laser Desorption Strategies for Ambient Molecular Mass Spectrometry N2 - Ambient mass spectrometry on a molecular level has become an indispensable analytical technique for the detection and characterization of organic molecules of different type, composition and size. Novel strategies, as well as fundamental and mechanistic research, has been successfully employed to obtain new hyphenated interrogation schemes, including laser ablation dielectric barrier discharge ionization (LA-DBDI) and laser ablation droplet ionization mass spectrometry (LDI-MS). To approach more complex analytical problems, development yielded in a hyphenated instrument using one shared high repetition rate laser for laser desorption mass spectrometry coupled to dielectric barrier discharge postionization and Raman scattering. Raman spectroscopy displays structural information. Mass spectrometry allows for an accurate determination of the molecular mass. Thus, a combination of LA-MS and optical spectroscopy could be highly beneficial for an unambiguous identification of complicated analytical samples. Acoustic levitation of droplets has matured to a powerful tool for containerless handling of microliter samples. In microfluidic systems the absence of confining walls is greatly beneficial because it can effectively suppress agglomeration and contamination of the sample originating at the liquid/solid interfaces. Here we present a set-up, utilizing the ?? = 2.94 µm output of a diode pumped Er:YAG laser for excitation, opening laser spray ionization to any OH-group containing solvents. To obtain deeper insights into ongoing laser desorption processes mechanistic studies have been carried out utilizing shadowgraphy experiments. Those nicely show the evaporation plume and its spatial distribution during a time period of up to 1 ms. Achieved results allow for further sensitivity improvement via a better ionization efficiency and a better subsequent ion transmission. T2 - Adlershofer Forschungsforum 2015 CY - Berlin, Deutschland DA - 2015-11-11 PY - 2015 AN - OPUS4-34948 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bierstedt, Andreas A1 - Warschat, Carsten A1 - You, Yi A1 - Rurack, Knut A1 - Riedel, Jens T1 - Stimulated Raman scattering by intracavity mixing of nanosecond laser excitation and fluorescence in acoustically levitated droplets N2 - Raman spectroscopy is becoming a commonly used, powerful tool for structural elucidation and species identification of small liquid samples, e.g. in droplet-based digital microfluidic devices. Due to the low scattering cross sections and the temporal restrictions dictated by the droplet flow, however, it depends on amplification strategies which often come at a cost. In the case of surface-enhanced Raman scattering (SERS), this can be an enhanced susceptibility towards memory effects and cross talk, whereas resonant and/or stimulated Raman techniques require higher instrumental sophistication, such as tunable lasers or the high electromagnetic field strengths which are typically provided by femtosecond lasers. Here, an alternative instrumental approach is discussed, in which stimulated Raman scattering (SRS) is achieved using the single fixed wavelength output of an inexpensive diode-pumped solid-state (DPSS) nanosecond laser. The required field strengths are realized by an effective light trapping in a resonator mode inside the interrogated droplets, while the resonant light required for the stimulation is provided by the fluorescence signal of an admixed laser dye. To elucidate the underlying optical processes, proof-of-concept experiments are conducted on acoustically levitated droplets, mimicking a highly reproducible and stable digital fluidic system. By using isotope-labeled compounds, the assignment of the emitted radiation as Raman scattering is firmly corroborated. A direct comparison reveals an amplification of the usually weak spontaneous Stokes emission by up to five orders of magnitude. Further investigation of the optical power dependence reveals the resulting gain to depend on the intensity of both, the input laser fluence and the concentration of the admixed fluorophore, leaving SRS as the only feasible amplification mechanism. While in this study stable large droplets have been studied, the underlying principles also hold true for smaller droplets, in which case significantly lower laser pulse energy is required. Since DPSS lasers are readily available with high repetition rates, the presented detection strategy bears a huge potential for fast online identification and characterization routines in digital microfluidic devices. KW - Ultrasonic levitation KW - Stimulated Raman Spectroscopy PY - 2020 U6 - https://doi.org/10.1039/D0AY01504K VL - 12 IS - 42 SP - 5046 EP - 5054 PB - Royal Society of Chemistry AN - OPUS4-51566 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bierstedt, Andreas A1 - Riedel, Jens T1 - Improving the performance of the laser-spark ion source for the detection of volatile organic compounds under ambient conditions N2 - Recently, a novel ionization scheme for ambient MS has been introduced. It is based on a quasi-continuous laser induced plasma (LIP), ignited in front of the MS inlet. This setup comprises the advantages of an ambient probe, electro neutrality, a sufficient duty cycle, a ubiquitous plasma medium, low power consumption, the absence of solvents and high sensitivity. To assess its future applicability for the detection of volatile organic compounds, plasma properties and operating conditions are investigated to understand the processes, that lead to the unexpected formation of intact molecular ions. Comprehensive studies include optical Emission spectroscopy, shadowgraphic shockwave visualization and time-of-flight mass spectrometry. T2 - 50. Jahrestagung der Deutschen Gesellschaft für Massenspektrometrie CY - Kiel, Germany DA - 05.03.2017 KW - Laser-spark KW - Laser induced plasma KW - Mass spectrometry KW - Ambient ionization PY - 2017 AN - OPUS4-39309 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - You, Yi A1 - Bierstedt, Andreas A1 - Riedel, Jens T1 - Spatial, temporal, and spectral characterization and kinetic investigations of a high repetition-rate laser-induced micro-plasma in air N2 - Advances in laser-induced plasmas have enabled various rapid and simple analytical applications. Especially, their uses in the analyses of condensed-phase samples have drawn significant attention in the past few decades. Depending on the laser energy per pulse, various analytical goals can be achieved. Laser-induced airborne plasmas allow direct analysis of species in ambient air. Importantly, all of these applications are based on a fundamental understanding of the laser–medium interaction. Recent developments of diode-pumped solid-state lasers offer an alternative to conventional powerful, yet bulky lasers, which can specifically operate at high Repetition rates. Although these lasers deliver much lower power per pulse (mJ compared to mJ), the outstanding repetition rates offer significant improvement to meet statistical needs in some cases. In the present work, a mJ-laserinduced airborne plasma was characterized through optical emission analysis. By using a ns-timegated image detector coupled with specific bandpass filters, spatially, temporally, and spectrally resolved plasma images were recorded. Compared to conventional mJ-laser-induced plasmas, the one induced by mJ-lasers demonstrated unique features during its evolution. Specifically, measurements of the distribution of ionic and atomic species revealed distinctive energy/matter transfer processes during early ignition of the plasma. Meanwhile, dynamic investigations suggested subsequent matter transport in the later stage. KW - Laser-induced plasma KW - Plasma KW - DPSS-laser PY - 2019 UR - https://pubs.rsc.org/en/content/articlehtml/2019/ja/c9ja00163h U6 - https://doi.org/10.1039/C9JA00163H SN - 0267-9477 VL - 34 IS - 8 SP - 1618 EP - 1629 PB - Royal Society of Chemistry CY - London AN - OPUS4-48622 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bierstedt, Andreas A1 - You, Yi A1 - van Wasen, Sebastian A1 - Bosc-Bierne, Gaby A1 - Weller, Michael G. A1 - Riedel, Jens T1 - Laser-Induced Microplasma as an Ambient Ionization Approach for the Mass-Spectrometric Analysis of Liquid Samples N2 - An airborne high repetition rate laser-induced plasma was applied as a versatile ambient ionization source for mass-spectrometric determinations of polar and nonpolar analytes in solution. The laser plasma was sustained between a home-built pneumatic nebulizer and the inlet capillary of an Orbitrap mass spectrometer. To maintain stable conditions in the droplet-rich spray environment, the plasma was directly fed by the fundamental output (λ = 1064 nm) of a current state-of-the-art diode-pumped solid-state laser. Ionization by the laser-driven plasma resulted in signals of intact analyte ions of several chemical categories. The analyte ions were found to be fully desolvated since no further increase in ion signal was observed upon heating of the inlet capillary. Due to the electroneutrality of the plasma, both positive and negative analyte ions could be formed simultaneously without altering the operational parameters of the ion source. While, typically, polar analytes with pronounced gas phase basicities worked best, nonpolar and amphoteric compounds were also detected. The latter were detected with lower ion signals and were prone to a certain degree of fragmentation induced during the ionization process. All the described attests the laser-induced microplasma by a good performance in terms of stability, robustness, sensitivity, and general applicability as a self-contained ion source for the liquid sample introduction. KW - Laser KW - Laser-induced plasma KW - Ambient ionization KW - Mass Spectrometry PY - 2019 U6 - https://doi.org/10.1021/acs.analchem.9b00329 SN - 0003-2700 VL - 91 IS - 9 SP - 5922 EP - 5928 PB - American Chemical Society CY - Washington, DC, USA AN - OPUS4-47939 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bierstedt, Andreas A1 - van Wasen, Sebastian A1 - Riedel, Jens T1 - Laser-spark ionization mass spectrometry N2 - 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, 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. T2 - European Mass Spectrometry Conference 2018 CY - Saarbrücken, Germany DA - 11.03.2018 KW - Laser-spark ionization KW - Laser-induced plasma KW - Ambient mass spectrometry KW - DPSS laser PY - 2018 AN - OPUS4-44492 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bierstedt, Andreas A1 - Stindt, Arne A1 - Warschat, Carsten A1 - Panne, Ulrich A1 - Riedel, Jens T1 - High repetition rate atmospheric pressure matrix-assisted laser desorption/ionization in combination with liquid matrices N2 - One major drawback of matrix-assisted laser desorption/ionization (MALDI) is still the relatively poor pulse-to-pulse reproducibility of the signal intensity. This problem, caused by insufficient homogeneity in the matrix/analyte co-crystallization, is usually circumvented by averaging the detected ion intensity over several shots. However, during the consecutive laser pulses, the applied matrix gets depleted and only a number of subsequent experiments can be done on the same sample spot. In order to achieve the desired long-term stability in combination with a sufficient pulse-to-pulse reproducibility, recently liquid MALDI matrices have been introduced. This contribution demonstrates the promising combination of liquid matrices with high repetition rate lasers for atmospheric pressure MALDI (AP-MALDI). To demonstrate the robustness of the new approach, two different kinds of liquid matrices were used in combination with both a typical flashlamp pumped 15 Hz laser and a diode pumped solid state laser operated at 5 kHz. The latter showed a stable ion signal over more than 3,500,000 consecutive laser pulses. KW - AP-MALDI KW - Liquid matrix KW - High repetition rate KW - Ionic liquid KW - DPSS laser PY - 2014 U6 - https://doi.org/10.1255/ejms.1292 SN - 1469-0667 SN - 1356-1049 SN - 1365-0718 VL - 20 IS - 5 SP - 367 EP - 374 PB - IM Publications CY - Chichester AN - OPUS4-32510 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bierstedt, Andreas A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Confinement and enhancement of an airborne atmospheric laser-induced plasma using an ultrasonic acoustic resonator N2 - Optical elemental analysis in the gas phase typically relies on electrically driven plasmas. As an alternative approach, laser-induced plasmas (LIPs) have been suggested but have so far been only scarcely used. Here, a novel signal enhancement strategy for laser-based airborne plasma optical Emission spectroscopy for gas phase analytics is presented. In contrast to an electrically driven plasma, in the laser-induced analogue dynamic matter transport equilibrium builds up. The latter results in a rarefied density regime in the plasma core itself, surrounded by an area of compressed matter. The central rarefaction leads to a decrease in plasma intensity and analyte number density, both of which are detrimental for analytical purposes. Since the repetitive ignition of LIPs is a transient process, a restoration of the former gaseous medium by other dynamically equilibrated diffusion processes would be favourable. The presented combination of an airborne LIP and an ultrasonic acoustic resonator yields a fourfold signal enhancement while the Background contribution of ubiquitous air is at the same time effectively suppressed. Since the entire enhancement effect occurs without contact, no additional sources for abrasive sample contamination are introduced. KW - DPSS laser KW - Laser-induced plasma KW - High repetition rate KW - Ultrasonic acoustic resonator KW - Optical emission spectroscopy PY - 2018 U6 - https://doi.org/10.1039/C7JA00297A SN - 0267-9477 SN - 1364-5544 VL - 33 IS - 1 SP - 135 EP - 140 PB - Royal Society of Chemistry CY - London AN - OPUS4-43619 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bierstedt, Andreas A1 - Stindt, Arne A1 - Warschat, Carsten A1 - Riedel, Jens A1 - Panne, Ulrich T1 - High repetitation rate AP-MALDI in combination with liquid matrices T2 - DGMS 2014 CY - Frankfurt am Main, Germany DA - 2014-03-02 PY - 2014 AN - OPUS4-30348 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bierstedt, Andreas A1 - Stindt, Arne A1 - Warschat, Carsten A1 - Riedel, Jens A1 - Panne, Ulrich T1 - Ionische Flüssigkeiten als Matrices für die AP-MALDI MS T2 - DGMS 2013 CY - Berlin, Germany DA - 2013-03-10 PY - 2013 AN - OPUS4-30347 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stindt, Arne A1 - Warschat, Carsten A1 - Bierstedt, Andreas A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Characterisation of an inexpensive sonic spray ionisation source using laser induced fluorescence imaging and mass spectrometry N2 - A commercially available airbrush gun as a new source for spray ionization is presented. It is best operated employing moderate stagnation pressures, resulting in a sonic gas flow. A mass spectrometric investigation on the amino acid lysine and several peptides reveals that this inexpensive approach results in reproducible mass spectra. The ion patterns strongly resemble the results from other studies obtained with custom made sonic spray vaporizers. The patterns as well resemble the mass spectra recorded with electrospray devices. For a better understanding of the vaporization process, the mass spectrometry experiments are accompanied by laser induced fluorescence experiments. Inverse Abel transform of the obtained fluorescence maps allows the determination of the full 3D distribution of the spray cone. Furthermore, via exploitation of the solvatochromism of the used dye the solvation state distribution can be visualized. In addition, expansion parameters like droplet size and velocity are obtained by laser stroboscopy. The experiments demonstrate that the analyte is hardly desolvated throughout the expansion. This indicates a subsequent vaporization of the residual solvent in the intermediate pressure region of the mass spectrometer. KW - Sonic spray ionization KW - Mass spectrometry KW - Solvatochromism KW - Inverse Abel Transform KW - Sonic spray KW - Airbrush KW - Laser induced fluorescence PY - 2014 U6 - https://doi.org/10.1255/ejms.1242 SN - 1469-0667 SN - 1356-1049 SN - 1365-0718 VL - 20 IS - 1 SP - 21 EP - 29 PB - IM Publications CY - Chichester AN - OPUS4-30403 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bierstedt, Andreas A1 - Riedel, Jens A1 - Panne, Ulrich T1 - Elucidation of reagent-ion formation in a versatile low-temperature plasma probe combining emission spectroscopy and ambient time-of-flight mass spectrometry T2 - Berliner Chemie Symposium 2015 CY - Berlin, Germany DA - 2015-04-09 PY - 2015 AN - OPUS4-33638 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bierstedt, Andreas A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Development of a new versatile instrument combining laser ablation mass spectrometry and laser emission spectroscopy T2 - 63rd ASMS Conference on Mass Spectrometry and Allied Topics CY - St. Louis, MO United States DA - 2015-05-31 PY - 2015 AN - OPUS4-33543 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bierstedt, Andreas A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Charactization of a versatile low temperature plasma torch by optical emission spectroscopy and time-of-flight mass spectrometry T2 - DGMS 2015 CY - Wuppertal, Deutschland DA - 2015-03-01 PY - 2015 AN - OPUS4-33639 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bierstedt, Andreas A1 - Panne, Ulrich A1 - Rurack, Knut A1 - Riedel, Jens T1 - Characterization of two modes in a dielectric barrier discharge probe by optical emission spectroscopy and time-of-flight-mass spectrometry N2 - Among the large number of new ambient ionization schemes in the last few years, dielectric barrier discharge (DBD) has witnessed special attention. In this contribution a versatile dual mode DBD is introduced and characterized by means of optical emission spectroscopy and time-of-flight mass spectrometry. A direct comparison of the individual results from spectroscopy, spectrometry and transient current/voltage consumption gives evidence for the existence of two individual operational mechanisms. The first is driven by rapid transient changes in the potential difference between the two electrodes over time (usually denoted as the homogeneous mode), while the second is caused at high static potential differences (leading to filamentary discharges). The transient versus steady-state characteristics of the individual discharge origin suggest the driving force for the current flow to be inductive and capacitive, respectively. In most cases of dielectric barrier plasmas both discharge types coexist as competitive ion formation channels, however, detailed plasma characteristics of DBDs operated under different conditions allow for a clear distinction of the individual contributions. In this way, two characteristic product channels for the ionization of ambient water could be observed resulting in the generation of either preferentially protonated water clusters or ammonium water clusters. Careful tuning of the operation parameters of the discharge device allows an operation predominated by either of the two modes. As a consequence, facile switching into the desired operational mode results in either protonated molecules or ammoniated molecules of the analyte. Plasma characteristics for both moieties were evaluated and cross-correlated on the basis of several factors including: the production of reagent ions, the individual appearance of current/voltage profiles, UV/Vis spectroscopy, voltage and flux dependence and the individual response to test compounds. Although the filamentary mode has been already discussed in the literature to induce fragmentation processes, no experimental evidence for analyte dissociation could be found in the case of the test compounds used KW - Dual mode KW - Dielectric barrier discharge KW - Ambient desorption/ionization mass spectrometry KW - Emission spectroscopy KW - Ionization PY - 2015 U6 - https://doi.org/10.1039/C5JA00332F SN - 0267-9477 SN - 1364-5544 VL - 30 IS - 12 SP - 2496 EP - 2506 PB - Royal Society of Chemistry CY - London AN - OPUS4-35092 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bierstedt, Andreas A1 - Kersten, H. A1 - Glaus, Reto A1 - Gornushkin, Igor B. A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Characterization of an airborne laser-spark ion source for ambient mass spectrometry N2 - An airborne laser plasma is suggested as an ambient ion source for mass spectrometry. Its fundamental physical properties, such as an excellent spatial and temporal definition, high electron and ion densities and a high effective cross section in maintaining the plasma, make it a promising candidate for future applications. For deeper insights into the plasma properties, the optical plasma emission is examined and compared to mass spectra. The results show a seemingly contradictory behavior, since the emitted light reports the plasma to almost entirely consist of hot elemental ions, while the corresponding mass spectra exhibit the formation of intact molecular species. Further experiments, including time- resolved shadowgraphy, spatially resolved mass spectrometry, as well as flow-dependent emission spectroscopy and mass spectrometry, suggest the analyte molecules to be formed in the cold plasma vicinity upon interaction with reactive species formed inside the hot plasma center. Spatial separation is maintained by concentrically expanding pressure waves, inducing a strong unidirectional diffusion. The accompanying rarefaction inside the plasma center can be compensated by a gas stream application. This replenishing results in a strong increase in emission brightness, in local reactive species concentration, and eventually in direct mass spectrometric sensitivity. To determine the analytical performance of the new technique, a comparison with an atmospheric pressure chemical ionization (APCI) source was conducted. Two kitchen herbs, namely, spearmint and basil, were analyzed without any sample pretreatment. The presented results demonstrate a considerably higher sensitivity of the presented laser-spark ionization technique. KW - Laser-spark KW - Laser induced plasma KW - Ambient mass spectrometry KW - Optical emission spectroscopy KW - Ionization PY - 2017 U6 - https://doi.org/10.1021/acs.analchem.6b04178 SN - 0003-2700 SN - 1520-6882 VL - 89 IS - 6 SP - 3437 EP - 3444 PB - American Chemical Society CY - Washington, DC, USA AN - OPUS4-39474 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bierstedt, Andreas A1 - Riedel, Jens A1 - Panne, Ulrich T1 - Combination of laser spectroscopy and laser ablation mass spectrometry T2 - IMSC 2014 CY - Geneva, Schweiz DA - 2014-08-24 PY - 2014 AN - OPUS4-31847 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -