TY - CONF A1 - Warschat, Carsten A1 - Stindt, Arne A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Improving the performance of an ultrasonic levitator coupled to API-TOF MS T2 - International Mass Spectrometry Conference 2014 CY - Geneva, Schweiz DA - 2014-08-24 PY - 2014 AN - OPUS4-31848 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Warschat, Carsten A1 - Stindt, Arne A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Spray-Ionisation mit einer handelsüblichen Airbrushpistole T2 - DGMS 2013 CY - Berlin, Germany DA - 2013-03-10 PY - 2013 AN - OPUS4-30345 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Warschat, Carsten A1 - Stindt, Arne A1 - Bierstedt, Andreas A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Charakterisierung einer Sonic Spray Ionisationsquelle mittels Laserinduzierter Fluoreszenz T2 - DGMS 2014 CY - Frankfurt am Main, Germany DA - 2014-03-02 PY - 2014 AN - OPUS4-30346 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Warschat, Carsten A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Whispering Gallery Modes in Acoustically Levitated Droplets T2 - Anakon 2015 CY - Graz, Österreich DA - 2015-03-23 PY - 2015 AN - OPUS4-33636 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Warschat, Carsten A1 - Stindt, Arne A1 - Bierstedt, Andreas A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Near-IR laser induced desorption sampling of acoustically levitated liquids T2 - Berliner Chemie Symposium 2015 CY - Berlin, Germany DA - 2015-04-09 PY - 2015 AN - OPUS4-33637 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Warschat, Carsten A1 - Stindt, Arne A1 - Bierstedt, Andreas A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Near-IR laser induced desorption sampling of acoustically levitated liquids T2 - DGMS 2015 CY - Wuppertal, Deutschland DA - 2015-03-01 PY - 2015 AN - OPUS4-33640 LA - deu 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 - CONF A1 - Warschat, Carsten A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Excitation of whispering gallery modes in acoustically levitated droplets T2 - 114th Gneral assembly of the German Bunsen Society for Physical Chemistry CY - Bochum, Germany DA - 2015-05-14 PY - 2015 AN - OPUS4-33544 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Warschat, Carsten A1 - Stindt, Arne A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Mass spectrometry of levitated droplets by thermally unconfined infrared-laser desorption N2 - An ionization scheme for fast online mass spectrometric interrogation of levitated droplets is presented. That renewed method comprises the output of an a Er:YAG laser at λ = 2.94 µm which is in resonance with the OH stretch vibration band of solvents like water and alcohols. A temporal pulse width larger than the time needed for pressure redistribution and also above the temperature redistribution time constant was found to lead to soft evaporation/ionization. Despite these mild desorption conditions, no additional postionization is found to be needed. Accordingly, the ionization is found to be very soft resulting in entirely intact analyte ions and concentration dependent cluster ions. Resulting mass spectra of small amino acids and large antibiotics are presented showing the versatility of the introduced technique. Above a critical mass of m ≈ 1 kDa, the formed ions carry multiple charges as it is typical for thermospray or electrospray ionization. The detection technique enables fast contactless analysis of the chemical composition of levitated microreactors and, thus, paves the way for future contactless reaction monitoring. KW - Laser desorption ionization KW - Levitated droplets KW - Ambient mass spectrometry PY - 2015 U6 - https://doi.org/10.1021/acs.analchem.5b01495 SN - 0003-2700 SN - 1520-6882 VL - 87 IS - 16 SP - 8323 EP - 8327 PB - American Chemical Society CY - Washington, DC AN - OPUS4-35134 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Warschat, Carsten A1 - Riedel, Jens T1 - Field-induced droplet ionization assisted by ultra sound N2 - Charge separation in liquid droplets within a strong electric field leads to opposite directed progeny droplet jets. That phenomenon is called field induced droplet ionization (FIDI). The jets contain charged molecules, which enables a mass spectrometric analysis. Acoustic levitation of droplets has matured to a powerful tool for containerless sample handling in micro fluidic systems in order to suppress agglomeration and classic contamination pathways. Herein we present the combination of both: FIDI assisted By Ultra-Sound (FIDIBUS). Compared to FIDI, it felicitates a steady observation of a single droplet during its jet formation. Furthermore, it allows for using different shaped electrodes and a multiple droplet interrogation. T2 - 49. Jahrestagung der Deutschen Gesellschaft für Massenspektrometrie CY - Hamburg, Germany DA - 28.02.2016 KW - Massenspektrometrie KW - Mass Spectrometry KW - Akustische Levitation KW - Acoustic Levitation KW - Feld-induzierte Tropfenionisation KW - Field-Induced Droplet Ionization PY - 2016 AN - OPUS4-35462 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 - 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 - JOUR A1 - Riedel, Jens A1 - Warschat, Carsten T1 - Studying the field induced breakup of acoustically levitated drops N2 - Coulomb fission of charged droplets (The terms drop and droplet are often used synonymous. Throughout this manuscript, to avoid confusion, the terms drop and droplet will be used for liquid spheres with radii in the millimeter range and the micrometer range, respectively. In our experiments, the first correspond to the parent drop while the latter describes the ejected progeny droplets.) is a wellstudied natural phenomenon. Controlled droplet fission is already successfully employed in several technological applications. Still, since the occurring surface rupture relies on the exact understanding and description of the liquid gas boundary, some details are still under debate. Most empirical systematic studies observe falling micrometer droplets passing through the electric field inside a plate capacitor. This approach, although easily applicable and reliable, limits the experimental degrees of freedom regarding the observable time and the maximum size of the drops and can only be performed in consecutive individual observations of different subsequent drops. Here we present a novel setup to study the field induced breakup of acoustically levitated drops. The design does not bear any restrictions towards the temporal window of observation, and allows handling of drops of a tunable radius ranging from 10 µm to several millimeters and a real-time monitoring of one single drop. Our comprehensive study includes a time resolved visual inspection, laser shadowgraphy, laser induced fluorescence imaging, and ambient mass spectrometric interrogation of the nascent Taylor cone. The results shown for a millimeter sized drop, previously inaccessible for Coulomb fission experiments, are mostly comparable with previous results for smaller drops. The major difference is the time scale and the threshold potential of the drop rupture. Both values, however, resemble theoretically extrapolations to the larger radius. The technique allows for a systematic study of breakup behavior of drops of different charge, material, and size. KW - Droplet fission KW - Levitated droplets KW - Taylor limit KW - Spray PY - 2017 U6 - https://doi.org/10.1063/1.5004046 SN - 0034-6748 SN - 1089-7623 VL - 88 IS - 10 SP - 105108-1 EP - 105108-6 PB - AIP publishing AN - OPUS4-42940 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -