@article{ZuehlkeZenichowskiRiebeetal.2017,
  author    = {Z{\"u}hlke, Martin and Zenichowski, Karl and Riebe, Daniel and Beitz, Toralf and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {Subambient pressure electrospray ionization ion mobility spectrometry},
  series = {International journal for ion mobility spectrometry : official publication of the International Society for Ion Mobility Spectrometry},
  volume    = {20},
  journal   = {International journal for ion mobility spectrometry : official publication of the International Society for Ion Mobility Spectrometry},
  publisher = {Springer},
  address   = {Heidelberg},
  issn      = {1435-6163},
  doi       = {10.1007/s12127-017-0215-x},
  pages     = {47 -- 56},
  year      = {2017},
  abstract  = {The pressure dependence of sheath gas assisted electrospray ionization (ESI) was investigated based on two complementary experimental setups, namely an ESI-ion mobility (IM) spectrometer and an ESI capillary - Faraday plate setup housed in an optically accessible vacuum chamber. The ESI-IM spectrometer is capable of working in the pressure range between 300 and 1000 mbar. Another aim was the assessment of the analytical capabilities of a subambient pressure ESI-IM spectrometer. The pressure dependence of ESI was characterized by imaging the electrospray and recording current-voltage (I-U) curves. Qualitatively different behavior was observed in both setups. While the current rises continuously with the voltage in the capillary-plate setup, a sharp increase of the current was measured in the IM spectrometer above a pressure-dependent threshold voltage. The different character can be attributed to the detection of different species in both experiments. In the capillary-plate experiment, a multitude of charged species are detected while only desolvated ions attribute to the IM spectrometer signal. This finding demonstrates the utility of IM spectrometry for the characterization of ESI, since in contrast to the capillary-plate setup, the release of ions from the electrospray droplets can be observed. The I-U curves change significantly with pressure. An important result is the reduction of the maximum current with decreasing pressure. The connected loss of ionization efficiency can be compensated by a more efficient transfer of ions in the IM spectrometer at increased E/N. Thus, similar limits of detection could be obtained at 500 mbar and 1 bar.},
  language  = {en}
}
@article{VillatoroZuehlkeRiebeetal.2016,
  author    = {Villatoro, Jos{\´e} Andr{\´e}s and Z{\"u}hlke, Martin and Riebe, Daniel and Beitz, Toralf and Weber, Marcus and Riedel, Jens and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {IR-MALDI ion mobility spectrometry: physical source characterization and application as HPLC detector},
  series = {International journal for ion mobility spectrometry : official publication of the International Society for Ion Mobility Spectrometry},
  volume    = {19},
  journal   = {International journal for ion mobility spectrometry : official publication of the International Society for Ion Mobility Spectrometry},
  publisher = {Springer},
  address   = {Heidelberg},
  issn      = {1435-6163},
  doi       = {10.1007/s12127-016-0208-1},
  pages     = {197 -- 207},
  year      = {2016},
  abstract  = {Infrared matrix-assisted laser dispersion and ionization (IR-MALDI) in combination with ion mobility (IM) spectrometry enables the direct analysis of biomolecules in aqueous solution. The release of ions directly from an aqueous solution is based on a phase explosion, induced by the absorption of an IR laser pulse, which disperses the liquid as vapor, nano-and micro-droplets. The ionization process is characterized initially by a broad spatial distribution of the ions, which is a result of complex fluid dynamics and desolvation kinetics. These processes have a profound effect on the shape and width of the peaks in the IM spectra. In this work, the transport of ions by the phase explosion-induced shockwave could be studied independently from the transport by the electric field. The shockwave-induced mean velocities of the ions at different time scales were determined through IM spectrometry and shadowgraphy. The results show a deceleration of the ions from 118 m.s(-1) at a distance of 400 mu m from the liquid surface to 7.1 m.s(-1) at a distance of 10 mm, which is caused by a pile-up effect. Furthermore, the desolvation kinetics were investigated and a first-order desolvation constant of 325 +/- 50 s(-1) was obtained. In the second part, the IR-MALDI-IM spectrometer is used as an HPLC detector for the two-dimensional separation of a pesticide mixture.},
  language  = {en}
}