TY - JOUR A1 - Salffner, Katharina A1 - Boehm, Michael A1 - Reich, Oliver A1 - Löhmannsröben, Hans-Gerd T1 - A broadband cavity ring-down spectrometer based on an incoherent near infrared light source JF - Applied physics : B, Lasers and optics Y1 - 2014 U6 - https://doi.org/10.1007/s00340-014-5762-9 SN - 0946-2171 SN - 1432-0649 VL - 116 IS - 4 SP - 785 EP - 792 PB - Springer CY - New York ER - TY - JOUR A1 - Bland-Hawthorn, Joss A1 - Ellis, S. C. A1 - Leon-Saval, S. G. A1 - Haynes, R. A1 - Roth, Martin M. A1 - Löhmannsröben, Hans-Gerd A1 - Horton, A. J. A1 - Cuby, J. -G. A1 - Birks, T. A. A1 - Lawrence, J. S. A1 - Gillingham, P. A1 - Ryder, S. D. A1 - Trinh, C. T1 - A complex multi-notch astronomical filter to suppress the bright infrared sky JF - Nature Communications N2 - A long-standing and profound problem in astronomy is the difficulty in obtaining deep near-infrared observations due to the extreme brightness and variability of the night sky at these wavelengths. A solution to this problem is crucial if we are to obtain the deepest possible observations of the early Universe, as redshifted starlight from distant galaxies appears at these wavelengths. The atmospheric emission between 1,000 and 1,800 nm arises almost entirely from a forest of extremely bright, very narrow hydroxyl emission lines that varies on timescales of minutes. The astronomical community has long envisaged the prospect of selectively removing these lines, while retaining high throughput between them. Here we demonstrate such a filter for the first time, presenting results from the first on-sky tests. Its use on current 8 m telescopes and future 30 m telescopes will open up many new research avenues in the years to come. Y1 - 2011 U6 - https://doi.org/10.1038/ncomms1584 SN - 2041-1723 VL - 2 IS - 50 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Cywinski, Piotr J. A1 - Olejko, Lydia A1 - Löhmannsröben, Hans-Gerd T1 - A time-resolved luminescent competitive assay to detect L-selectin using aptamers as recognition elements JF - Analytica chimica acta : an international journal devoted to all branches of analytical chemistry N2 - L-selectin is a protein with potential importance for numerous diseases and clinical disorders. In this paper, we present a new aptamer-based luminescent assay developed to detect L-selectin. The sensing system working principle is based on Forster Resonance Energy Transfer (FRET) from a donor terbium complex (TbC) to an acceptor cyanine dye (Cy5). In the present approach, the biotinylated aptamer is combined with Cy5-labelled streptavidin (Cy5-Strep) to yield an aptamer-based acceptor construct (Apta-Cy5-Strep), while L-selectin is conjugated using luminescent TbC. Upon aptamer binding to the TbC-labelled L-selectin (L-selectin-TbC), permanent donor-acceptor proximity is established which allows for radiationless energy transfer to occur. However, when unlabelled L-selectin is added, it competes with the L-selectin-TbC and the FRET signal decreases as the L-selectin concentration increases. FRET from the TbC to Cy5 was observed with time-gated time-resolved luminescence spectroscopy. A significant change in the corrected luminescence signal was observed in the dynamic range of 10 -500 ng/mL L-selectin, the concentration range relevant for accelerated cognitive decline of Alzheimer's disease, with a limit of detection (LOD) equal to 10 ng/mL. The aptasensor-based assay is homogeneous and can be realized within one hour. Therefore, this method has the potential to become an alternative to tedious heterogeneous analytical methods, e.g. based on enzyme-linked immunosorbent assay (ELISA). (C) 2015 Elsevier B.V. All rights reserved. KW - Aptamer KW - FRET KW - L-selectin KW - Luminescence spectroscopy KW - Fluoroassay KW - Lanthanide Y1 - 2015 U6 - https://doi.org/10.1016/j.aca.2015.06.045 SN - 0003-2670 SN - 1873-4324 VL - 887 SP - 209 EP - 215 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Zühlke, Martin A1 - Riebe, Daniel A1 - Beitz, Toralf A1 - Löhmannsröben, Hans-Gerd A1 - Zenichowski, Karl A1 - Diener, Marc A1 - Linscheid, Michael W. T1 - An electrospray ionization-ion mobility spectrometer as detector for high-performance liquid chromatography JF - European journal of mass spectrometry N2 - The application of electrospray ionization (ESI) ion mobility (IM) spectrometry on the detection end of a high-performance liquid chromatograph has been a subject of study for some time. So far, this method has been limited to low flow rates or has required splitting of the liquid flow. This work presents a novel concept of an ESI source facilitating the stable operation of the spectrometer at flow rates between 10 mu L min(-1) and 1500 mu L min(-1) without flow splitting, advancing the T-cylinder design developed by Kurnin and co-workers. Flow rates eight times faster than previously reported were achieved because of a more efficient dispersion of the liquid at increased electrospray voltages combined with nebulization by a sheath gas. Imaging revealed the spray operation to be in a rotationally symmetric multijet-mode. The novel ESI-IM spectrometer tolerates high water contents (<= 90%) and electrolyte concentrations up to 10 mM, meeting another condition required of high-performance liquid chromatography (HPLC) detectors. Limits of detection of 50 nM for promazine in the positive mode and 1 mu M for 1,3-dinitrobenzene in the negative mode were established. Three mixtures of reduced complexity (five surfactants, four neuroleptics, and two isomers) were separated in the millisecond regime in stand-alone operation of the spectrometer. Separations of two more complex mixtures (five neuroleptics and 13 pesticides) demonstrate the application of the spectrometer as an HPLC detector. The examples illustrate the advantages of the spectrometer over the established diode array detector, in terms of additional IM separation of substances not fully separated in the retention time domain as well as identification of substances based on their characteristic IMs. KW - ESI KW - IMS KW - HPLC KW - spray imaging KW - neuroleptics KW - pesticides KW - surfactants Y1 - 2015 U6 - https://doi.org/10.1255/ejms.1367 SN - 1469-0667 SN - 1751-6838 VL - 21 IS - 3 SP - 391 EP - 402 PB - WeltTrends CY - Sussex ER - TY - GEN A1 - Schmälzlin, Elmar A1 - Dongen, Joost T. van A1 - Klimant, Ingo A1 - Marmodée, Bettina A1 - Steup, Martin A1 - Fishahn, Joachim A1 - Geigenberger, Peter A1 - Löhmannsröben, Hans-Gerd T1 - An optical multifrequency phase-modulation method using microbeads for measuring intracellular oxygen concentrations in plants N2 - A technique has been developed to measure absolute intracellular oxygen concentrations in green plants. Oxygen-sensitive phosphorescent microbeads were injected into the cells and an optical multifrequency phase-modulation technique was used to discriminate the sensor signal from the strong autofluorescence of the plant tissue. The method was established using photosynthesis-competent cells of the giant algae Chara corallina L., and was validated by application to various cell types of other plant species. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 007 Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12232 ER - TY - JOUR A1 - Riebe, Daniel A1 - Eder, Alexander A1 - Ritschel, Thomas A1 - Beitz, Toralf A1 - Löhmannsröben, Hans-Gerd A1 - Beil, Andreas A1 - Blaschke, Michael A1 - Ludwig, Thomas T1 - Atmospheric pressure chemical ionization of explosives induced by soft X-radiation in ion mobility spectrometry: mass spectrometric investigation of the ionization reactions of drift gasses, dopants and alkyl nitrates JF - Journal of mass spectrometr N2 - A promising replacement for the radioactive sources commonly encountered in ion mobility spectrometers is a miniaturized, energy-efficient photoionization source that produce the reactant ions via soft X-radiation (2.8 keV). In order to successfully apply the photoionization source, it is imperative to know the spectrum of reactant ions and the subsequent ionization reactions leading to the detection of analytes. To that end, an ionization chamber based on the photoionization source that reproduces the ionization processes in the ion mobility spectrometer and facilitates efficient transfer of the product ions into a mass spectrometer was developed. Photoionization of pure gasses and gas mixtures containing air, N-2, CO2 and N2O and the dopant CH2Cl2 is discussed. The main product ions of photoionization are identified and compared with the spectrum of reactant ions formed by radioactive and corona discharge sources on the basis of literature data. The results suggest that photoionization by soft X-radiation in the negative mode is more selective than the other sources. In air, adduct ions of O-2 - with H2O and CO2 were exclusively detected. Traces of CO2 impact the formation of adduct ions of O-2 - and Cl -(upon addition of dopant) and are capable of suppressing them almost completely at high CO2 concentrations. Additionally, the ionization products of four alkyl nitrates (ethylene glycol dinitrate, nitroglycerin, erythritol tetranitrate and pentaerythritol tetranitrate) formed by atmospheric pressure chemical ionization induced by X-ray photoionization in different gasses (air, N-2 and N2O) and dopants (CH2Cl2, C2H5Br and CH3I) are investigated. The experimental studies are complemented by density functional theory calculations of the most important adduct ions of the alkyl nitrates (M) used for their spectrometric identification. In addition to the adduct ions [M + NO3](-) and [M + Cl](-), adduct ions such as [M + N2O2](-), [M + Br](-) and [M+ I](-) were detected, and their gas-phase structures and energetics are investigated by density functional theory calculations. Copyright (C) 2016 John Wiley & Sons, Ltd. KW - ion mobility spectrometry KW - mass spectrometry KW - explosives KW - X-ray KW - photoionization KW - alkyl nitrates Y1 - 2016 U6 - https://doi.org/10.1002/jms.3784 SN - 1076-5174 SN - 1096-9888 VL - 51 SP - 566 EP - 577 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Riebe, Daniel A1 - Zühlke, Martin A1 - Zenichowski, Karl A1 - Beitz, Toralf A1 - Dosche, Carsten A1 - Löhmannsröben, Hans-Gerd T1 - Characterization of rhodamine 6G release in electrospray ionization by means of spatially resolved fluorescence spectroscopy JF - Zeitschrift für physikalische Chemie : international journal of research in physical chemistry and chemical physics N2 - In the present work, the density distribution of rhodamine 6G ions (R6G) in the gas phase and the droplets of an electrospray plume was studied by spatial and spectral imaging. The intention is to contribute to the fundamental understanding of the release mechanism of gaseous R6G in the electrospray ionization (ESI) process. Furthermore, the influence of ESI-parameters on the release efficiency of R6G, e. g. solvent flow, R6G and salt concentration were examined via direct fluorescence imaging of R6G. A solvent-shift of the fluorescence maximum,lambda(max) = 555 nm in methanolic solution and lambda(max) = 505 nm in gas phase, allows the discrimination between solvated and gaseous R6G. Two experimental setups were used for our measurements. In the first experiment, the R6G fluorescence and the light scattered from the spray plume were imaged in two spatial dimensions using a tunable wavelength filter. The second experiment was designed for obtaining 1-dimensional spatially resolved emission spectra of the spray. Here, the intensity distribution of solvated and gaseous R6G as well as scattered light (lambda = 355 nm) were measured simultaneously. The results show the distribution of gaseous R6G in the plane, orthogonal to the ESI capillary, decreasing slightly towards the spray center and showing maxima at the cone margins. The distribution of gaseous R6G confirms the preferred release of gaseous ions from nano-droplets, indicating the ion evaporation model (IEM) to be the dominating release mechanism. Up to now, only a few fluorescence spectra of ionic compounds in the gas phase were published because the measurement of emission spectra of mass-selected ions in an ion trap is experimentally challenging. The fluorescence spectrum of gaseous lucigenin at atmospheric pressure is reported for the first time. This spectrum of lucigenin in the gas phase exhibits a blue shift of about Delta lambda = 10 nm in comparison to the corresponding spectrum in methanol. KW - Fluorescence KW - Electrospray Ionization KW - Rhodamine 6G KW - Gaseous Ions KW - Lucigenin Y1 - 2011 U6 - https://doi.org/10.1524/zpch.2011.0149 SN - 0942-9352 VL - 225 IS - 9-10 SP - 1055 EP - 1072 PB - De Gruyter Oldenbourg CY - München ER - TY - JOUR A1 - Erler, Alexander A1 - Riebe, Daniel A1 - Beitz, Toralf A1 - Löhmannsröben, Hans-Gerd A1 - Grothusheitkamp, Daniela A1 - Kunz, Thomas A1 - Methner, Frank-Jürgen T1 - Characterization of volatile metabolites formed by molds on barley by mass and ion mobility spectrometry JF - Journal of mass spectrometr N2 - The contamination of barley by molds on the field or in storage leads to the spoilage of grain and the production of mycotoxins, which causes major economic losses in malting facilities and breweries. Therefore, on-site detection of hidden fungus contaminations in grain storages based on the detection of volatile marker compounds is of high interest. In this work, the volatile metabolites of 10 different fungus species are identified by gas chromatography (GC) combined with two complementary mass spectrometric methods, namely, electron impact (EI) and chemical ionization at atmospheric pressure (APCI)-mass spectrometry (MS). The APCI source utilizes soft X-radiation, which enables the selective protonation of the volatile metabolites largely without side reactions. Nearly 80 volatile or semivolatile compounds from different substance classes, namely, alcohols, aldehydes, ketones, carboxylic acids, esters, substituted aromatic compounds, alkenes, terpenes, oxidized terpenes, sesquiterpenes, and oxidized sesquiterpenes, could be identified. The profiles of volatile and semivolatile metabolites of the different fungus species are characteristic of them and allow their safe differentiation. The application of the same GC parameters and APCI source allows a simple method transfer from MS to ion mobility spectrometry (IMS), which permits on-site analyses of grain stores. Characterization of IMS yields limits of detection very similar to those of APCI-MS. Accordingly, more than 90% of the volatile metabolites found by APCI-MS were also detected in IMS. In addition to different fungus genera, different species of one fungus genus could also be differentiated by GC-IMS. KW - APCI KW - fungus KW - gas chromatography KW - ion mobility spectrometry KW - mass KW - spectrometry KW - mold KW - soft X-ray Y1 - 2020 U6 - https://doi.org/10.1002/jms.4501 SN - 1076-5174 SN - 1096-9888 VL - 55 IS - 5 SP - 1 EP - 10 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Schwarze, Thomas A1 - Dosche, Carsten A1 - Flehr, Roman A1 - Klamroth, Tillmann A1 - Löhmannsröben, Hans-Gerd A1 - Saalfrank, Peter A1 - Cleve, Ernst A1 - Buschmann, Hans-Jürgen A1 - Holdt, Hans-Jürgen T1 - Combination of a CT modulated PET and an intramolecular excimer formation to quantify PdCl2 by large fluorescence enhancement N2 - The [6.6](9,10)anthracenophane 1 (Scheme 1) is a selective fluoroionophore for the detection of PdCl2 with a large fluorescence enhancement factor (I/I-0 > 250). Y1 - 2010 UR - http://pubs.rsc.org/en/content/articlehtml/2010/cc/b919973j U6 - https://doi.org/10.1039/B919973j SN - 1359-7345 ER - TY - JOUR A1 - Schwarze, Thomas A1 - Dosche, Carsten A1 - Flehr, Roman A1 - Klamroth, Tillmann A1 - Löhmannsröben, Hans-Gerd A1 - Saalfrank, Peter A1 - Cleve, Ernst A1 - Buschmann, Hans-Jürgen A1 - Holdt, Hans-Jürgen T1 - Combination of a CT modulated PET and an intramolecular excimer formation to quantify PdCl2 by large fluorescence enhancement Y1 - 2010 UR - http://www.rsc.org/ej/CC/2010/b919973j.pdf SN - 1359-7345 ER -