TY - JOUR A1 - Shelley, J.T. A1 - Stindt, Arne A1 - Riedel, Jens A1 - Engelhard, C. T1 - Time-resolved mass-spectral characterization of ion formation from a low-frequency, low-temperature plasma probe ambient ionization source N2 - New-found interest in the development of ionization sources for mass spectrometry, inspired by the advent of ambient desorption/ionization mass spectrometry, has led to a resurgence in plasma-source development and characterization. Dielectric-barrier discharges, particularly the low-temperature plasma (LTP) probe format, have been at the forefront of this field due to their low power consumption and relatively simple design. However, better fundamental understanding of this desorption/ionization source is needed to improve the analytical capabilities of such a device. Here, we use relatively fast (2.5 ms per spectrum) time-resolved mass spectrometry to characterize the temporal reagent-ion distribution from a low-frequency LTP probe. Different voltage waveforms were found to heavily influence the discharge properties and, consequently, ion production. Ion signals from short discharge pulses, ca. 40 µs, were found to be significantly broadened, ca. 10 ms, prior to extraction into the mass spectrometer. Additionally, higher frequencies of a sine-wave LTP produced the largest flux of reagent ions, which existed for most of the voltage waveforms. Finally, temporal signals for reagent and analyte ions were measured and related to specific ionization processes: proton transfer and charge transfer. KW - Time resolved KW - Mass spectrometry KW - Time of flight KW - Dielectric barrier discharge KW - Plasma KW - Atmospheric-pressure KW - Emission-spectrometry KW - Surface treatment PY - 2014 DO - https://doi.org/10.1039/c3ja50318f SN - 0267-9477 SN - 1364-5544 VL - 29 IS - 2 SP - 359 EP - 366 PB - Royal Society of Chemistry CY - London AN - OPUS4-30404 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stindt, Arne T1 - CO2-Laser Atmospheric Pressure Ionization of Acoustically Levitated Droplets T2 - IMSC CY - Kyoto, Japan DA - 2012-09-15 PY - 2012 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. AN - OPUS4-27333 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stindt, Arne T1 - CO2-Laser Atmospheric Pressure Ionization of Acoustically Levitated Droplets T2 - Doktorandenseminar Spektroskopie und Spurenanalytik 2012 CY - Mainz, Germany DA - 2012-07-09 PY - 2012 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. AN - OPUS4-27328 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stindt, Arne T1 - CO2-Laser Atmospheric Pressure Ionization of Acoustically Levitated Droplets T2 - Tokyo Tech (invited Talk) CY - Tokyo, Japan DA - 2012-09-28 PY - 2012 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. AN - OPUS4-27329 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stindt, Arne T1 - CO2-Laser Atmospheric Pressure Ionization of Acoustically Levitated Droplets T2 - DGMS Jahrestagung CY - Poznan, Poland DA - 2012-03-04 PY - 2012 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. AN - OPUS4-27327 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stindt, Arne T1 - Atmosphärendruck-Ionisation levitierter Tröpfchen T2 - DGMS 2013 CY - Berlin, Germany DA - 2013-03-10 PY - 2013 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. AN - OPUS4-30350 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stindt, Arne T1 - Characterization of Pressure Field Distribution for an Optimization of Ultrasonic Levitatiors T2 - ANAKON 2013 CY - Essen, Germany DA - 2013-03-04 PY - 2013 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. AN - OPUS4-30351 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 DO - 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 - Stindt, Arne A1 - Andrade, M. A. B. A1 - Buurman, Merwe A1 - Adamowski, J. C. A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Experimental and numerical characterization of the sound pressure in standing wave acoustic levitators N2 - A novel method for predictions of the sound pressure distribution in acoustic levitators is based on a matrix representation of the Rayleigh integral. This method allows for a fast calculation of the acoustic field within the resonator. To make sure that the underlying assumptions and simplifications are justified, this approach was tested by a direct comparison to experimental data. The experimental sound pressure distributions were recorded by high spatially resolved frequency selective microphone scanning. To emphasize the general applicability of the two approaches, the comparative studies were conducted for four different resonator geometries. In all cases, the results show an excellent agreement, demonstrating the accuracy of the matrix method. KW - Acoustic levitation KW - Matrix calculation KW - Microphony KW - Noncontact ultrasonic transportation KW - Small objects KW - Matrix-method KW - Droplets KW - Air KW - Manipulation KW - Simulation KW - Fields KW - Water PY - 2014 DO - https://doi.org/10.1063/1.4861197 SN - 0034-6748 SN - 1089-7623 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. VL - 85 IS - 015110 SP - 1 EP - 6 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-30405 LA - eng 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 DO - 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 -