TY - JOUR AB - Crosslinking mass spectrometry (XL-MS) has emerged as a powerful tool in its own right for the investigation of protein structures and interactions. Utilizing standard shotgun MS mass spectrometry equipment and specialized database search software, crosslinked peptide-pairs can be identified and directly translated into distance constraints for protein structure and protein-protein interaction investigations. Whereas the gas-phase dissociation behavior of linear peptides is well understood, less is however known about the gas-phase dissociation behavior of crosslinked peptides. In this work, we set out to expose the behavior of commonly used non-cleavable and gas-phase cleavable crosslinking reagents using synthetic peptides to establish mechanistic insights. We describe that crosslinked peptide pairs generate specific fragmentation patterns and diagnostic ions under HCD and CID fragmentation conditions, distinct from mono-linked peptide and non-modified peptides. We discuss in detail the resulting diagnostic ions that can help distinguishing linear peptides from mono-linked and crosslinked peptide pairs and how that may be used to further increase the efficiency of XL-MS analysis. (C) 2019 Elsevier B.V. All rights reserved. AU - Steigenberger, B.* AU - Schiller, H. B. AU - Pieters, R.J.* AU - Scheltema, R.A.* C1 - 56681 C2 - 47175 CY - Radarweg 29, 1043 Nx Amsterdam, Netherlands TI - Finding and using diagnostic ions in collision induced crosslinked peptide fragmentation spectra. JO - Int. J. Mass Spectrom. VL - 444 PB - Elsevier PY - 2019 SN - 1387-3806 ER - TY - JOUR AB - The hot-water extraction process used to make an espresso coffee is affected by a large number of factors. A proper understanding of how these factors impact the profile of the final cup is important to the quality of an espresso coffee. This work examines the effect of water temperature and pressure on the extraction kinetics of volatile organic compounds (VOCs) in coffee. This was achieved by on-line monitoring of the volatiles directly from the coffee flow, using proton-transfer-reaction time-of-flight mass-spectrometry (PTR-ToF-MS). Using hierarchical cluster analysis (HCA), tentatively identified compounds were grouped into 5 families according to their time-intensity profiles. VOCs grouped into each family had similar physicochemical properties while polarity was found to be one of the main forces driving VOC extraction kinetics. The effect of pressure was studied by extracting espresso coffees at 7, 9 and 11. bar. A pressure of 11. bar resulted in an increased extraction of volatiles over the entire extraction time (25. s). To study the effect of temperature, espresso coffees were extracted at 82, 92 and 96. °C. An increase in temperature produced a significant increase in the extraction of VOCs, especially during the last part of the extraction. The effect of temperature on extractability was more pronounced for the less polar compounds. AU - Sánchez López, J.A.* AU - Wellinger, M.* AU - Gloess, A.N.* AU - Zimmermann, R. AU - Yeretzian, C.* C1 - 48108 C2 - 39930 CY - Amsterdam SP - 22-30 TI - Extraction kinetics of coffee aroma compounds using a semi-automatic machine: On-line analysis by PTR-ToF-MS. JO - Int. J. Mass Spectrom. VL - 401 PB - Elsevier Science Bv PY - 2016 SN - 1387-3806 ER - TY - JOUR AB - After characterizing the negative ion chemistry of tris(trifluoromethyl) phosphine in a previous work, new insights about the interpretation of the MS/MS mass spectrum of the phosphide anion (CF3)2P- m/z 169 could be revealed and are described in this current work. The phosphide (CF3)2P- anion, m/z 169, was accelerated in a cloud of (CF3)3P neutrals and new product ions could be detected which do not belong to fragmentation channels. Instead, high mass anions m/z 207 and m/z 257 are found, and the reaction mechanism could be revealed by density functional theory (DFT) calculations at B3LYP/6-311 + G(3df)//B3LYP/6-31 + G(2d) level of theory. The formation of the phosphoranide (CF3)3PF- m/z 257 is the result of a fluoride anion transfer from the accelerated phosphide anion (CF3) 2P- m/z 169 to the (CF3)3P neutral m = 238. Decomposition of the newly formed phosphoranide (CF3) 3PF- m/z 257 leads to the formation of smaller phosphoranides (CF3)2PF2 - m/z 207 and CF3PF3 - m/z 157 as a result of successive CF2 eliminations. A new rearrangement in the formed phosphoranide (CF3)2PF2 - could be revealed, whereby a CC bond formation can take place and the product anion C 2F5 - m/z 119 could be experimentally obtained. AU - Kanawati, B. AU - Wanczek, K.-P.* C1 - 31098 C2 - 34189 CY - Amsterdam SP - 18-23 TI - Phosphoranide production and decomposition in the gas phase. JO - Int. J. Mass Spectrom. VL - 362 IS - 1 PB - Elsevier Science Bv PY - 2014 SN - 1387-3806 ER - TY - JOUR AB - In the preceding paper an approach was described that allows measured secondary-ion energy spectra to be correlated with the original energy distribution. Here the model was applied to analyse energy spectra of Cs+ ions sputtered from a Cs bombarded Si sample. The aim was to show that relevant properties of the employed IMS-4f sector field mass spectrometers as well as the mean surface binding energy of the Cs+ ions can be derived in one effort. The novel results may be summarised as follows. (i) The width of the energy slit can be determined in situ by comparing integral intensities for the chosen and the fully opened slit, the latter of known size. (ii) Pronounced yield losses occur if the width-to-thickness ratio of the slit is reduced below about 0.1. (iii) The broadening of energy spectra is predominantly defined by the slit width. Unexpectedly, the size of the circular contrast aperture plays only a minor role. The reason needs to be clarified. (iv) Measured spectra can be reproduced with a remarkable accuracy, better than +/- 8% throughout the whole spectrum. The origin of the energy scale can be determined with an uncertainty of +/- 0.05 eV. (v) Beyond a characteristic energy E-c the transmission decreases more rapidly with increasing emission energy E than the expected E-c/E fall-off. The difference is probably due to the detuning of the immersion lens, an action inevitably associated with increasing target-bias offset. (vi) The surface binding energy E-s of Cs+ ions, derived from spectra measured with the largest contrast aperture, turned out to be surprisingly high, 3.9 +/- 0.2 eV. Evidently, the Cs+ ions were emitted from sites featuring very strong ionic bonding. The derived value of E-s presumably represents the centroid (E-s) of a spectrum of binding energies which reflect different local configurations of damage around the Cs ions. Considering the much lower binding energy of adsorbed Cs atoms, we have to conclude that sputtered ions and neutrals do not exhibit the same energy spectrum. Hence the previous practise of using one global ionisation probability to correlate secondary ion emission with the sputtering of neutral atoms needs to be abandoned. AU - Wittmaack, K. AU - Gnaser, H.* C1 - 30634 C2 - 33753 SP - 49-58 TI - Comprehensive modelling of secondary-ion energy spectra measured with a magnetic sector field instrument: II. Evaluation of experimental data. JO - Int. J. Mass Spectrom. VL - 358 IS - 1 PB - Elsevier Science PY - 2014 SN - 1387-3806 ER - TY - JOUR AB - In order to correlate measured secondary-ion energy spectra with theoretically predicted energy distributions of sputtered atoms, one needs to know the properties of the employed mass spectrometer. Here the resolution function and the transmission of a frequently employed magnetic sector-field instrument (IMS-nf series) are described using a simple concept. Modelling of energy spectra is greatly facilitated by the recently provided evidence that the ionisation probability of secondary ions is independent of their emission velocity. Hence the ejected ions may be described by Thompson-type energy distributions which are fully defined by the surface binding energy, Es, of sputtered atoms. On passage through the mass spectrometer the energy distributions are modified in response to the energy dependent transmission of the ion optical system, the aberrations of the lenses and the non-negligible size of the resolution defining apertures, notably the circular contrast aperture (CA) on the entrance side of the spherical energy analyser (aperture diameter d) and the energy slit on the exit side (slit width s). The diameter d determines a characteristic energy Ec up to which secondary ions with emission angles up to 90° to the surface normal are fed through the CA. At higher energies the transmission theoretically decreases as 1/E. Resolution functions are derived by convolving a rectangular box of unit height and width ω with a Gaussian featuring a standard deviation σ. The shape, width and height of the modelled energy spectra depend in a characteristic manner on ω, σ, Ec and Es. Owing to the very low characteristic energies (Ec ≤ 0.1 eV) associated with small CAs (d ≤ 50 μm), the resulting energy spectra contain very little useful information on the physics of the emission process. The peak position and the width of energy distributions are reproduced best using contrast apertures large enough to achieve Ec > 2Es, in combination with a slit width corresponding to ω < Es/4. Inspecting calculated spectra on absolute scales, variations of ω are seen to shift the low-energy edge towards lower ('negative') energies by ω/2. With Es as an input parameter, the true origin of the energy scale may be assessed with an accuracy of about ±0.05 eV. In measured spectra, the full widths at half maximum of the original distribution and the resolution function add up roughly in quadrature. Evidence in favour of the described concept is presented in the companion paper. AU - Wittmaack, K. C1 - 28569 C2 - 33459 CY - Amsterdam SP - 55-63 TI - Comprehensive modelling of secondary-ion energy spectra measured with a magnetic sector field instrument: I. Concept and basic features. JO - Int. J. Mass Spectrom. VL - 359 IS - 1 PB - Elsevier Science PY - 2014 SN - 1387-3806 ER - TY - JOUR AU - Wittmaack, K. AU - Gnaser, H.* C1 - 32746 C2 - 35548 CY - Amsterdam SP - 64 TI - Erratum to "Comprehensive modelling of secondary-ion energy spectra measured with a magnetic sector field instrument: II. Evaluation of experimental data" (Int. J. Mass Spectrom. (2013) 358 (49-58)). JO - Int. J. Mass Spectrom. VL - 359 IS - 1 PB - Elsevier Science Bv PY - 2014 SN - 1387-3806 ER - TY - JOUR AB - A set of 14 stacked ring electrodes was studied by the SIMION ion trajectory simulation program under a pressure of 1 Pa with different applied RF frequencies and RF voltage amplitudes when a classical DC gradient of 38 V/cm is applied. Ion–neutral collision effects were considered by adopting a successful and integrated hard sphere, elastic, ion–neutral collision user program provided by SIMION. Mass dependent ion transmission efficiencies could be obtained. In the classical operation mode of the ion beam guide, a RF frequency of 2 MHz was crucial to obtain very good ion transmission efficiency along a broad mass range. Lower RF frequencies (<1.5 MHz) limited the good transmission efficiencies only to high masses with m/z > 500 amu. SIMION can reproduce expected efficiency curves which show that low m/z ions below 150 amu represent a challenge for such linear ion beam devices even when high RF driving frequency of 2 MHz is applied. The simulations also show that a DC gradient of at least 30 V/cm is crucial to maintain good transmission efficiencies which are in agreement with previously published results. A new operation mode for running the same device is introduced for earlier ion focusing in between the second and fifth ring electrodes, prior to slight beam divergence after the focus point. This required a significant change of the applied DC voltages to alter the shape of the DC gradient curve along the central z axis. The newly identified operation mode allows enhancing the mass dependent ion transmission efficiency in a wide m/z range between 80 and 1000 amu when an RF frequency of 2 MHz is applied to the first ten ring electrodes. AU - Kanawati, B. AU - Wanczek, K.-P.* AU - Gebefügi, I. AU - Schmitt-Kopplin, P. C1 - 8447 C2 - 30125 SP - 25-29 TI - Prefocusing inside a linear ion beam guide - a SIMION study. JO - Int. J. Mass Spectrom. VL - 325 PB - Elsevier PY - 2012 SN - 1387-3806 ER - TY - JOUR AB - Secondary ion mass spectrometry (SIMS) is an established technique for sensitive compositional analysis of solids. To achieve high sensitivity in the so-called dynamic SIMS mode, notably in the analysis of negative secondary ions, it is common practice to use Cs primary ions for sputter erosion as well as for loading the sample with Cs. In qualitative terms, the negative-ion yield enhancement has been attributed to a lowering of the sample's work function but, remarkably, the physical processes involved in producing the favorable conditions have not been clarified in any detail before. This study provides evidence that work function changes observed under Cs bombardment can be explained if the implanted ions are transiently converted to adatoms. Previously disregarded properties of Cs atoms include the huge size, the high mobility and bond formation with coverage dependent strength. It is shown that implanted Cs atoms are rapidly relocated towards the receding surface, presumably in response to the stress generated by the retained material. After passage through the solid-vacuum interface, Cs atoms loose their valance electron and become bound to the surface via dipole interaction. This way they become adatoms. Stationary conditions in terms of Cs surface coverage are established by the balance between adatom formation and sputter ejection at energies exceeding the bond strength. Combining calculated sputter cross sections for adatom removal with experimental data from various sources, the rates of Cs implantation and reemission are shown to be in balance with an uncertainty of only about +/- 20%. AU - Wittmaack, K. C1 - 7391 C2 - 29698 SP - 68-72 TI - Mechanisms responsible for inducing and balancing the presence of Cs adatoms in dynamic Cs based SIMS. JO - Int. J. Mass Spectrom. VL - 313 PB - Elsevier PY - 2012 SN - 1387-3806 ER - TY - JOUR AB - Isotope dilution in thermal ionization mass spectrometry (ID-TIMS) is a precise method for quantification of isotope ratios in geological samples, or for trace elements analysis in geological and environmental samples. This work presents an optimized ID-TIMS method for application in the field of life sciences, more precisely in the frame of a human biokinetic study on zirconium with oral and intravenous administration of two stable isotope tracers. The method allows analyzing simultaneously different stable zirconium isotopes (two isotopically enriched artificial tracers and the natural background) in human blood plasma and urine. By optimization, tracer detection limits below 1 ng ml(-1) could be achieved. The biological samples were prepared by microwave-assisted acidic pressure digestion followed by extraction chromatography. The purified zirconium from the samples was measured on carbon-coated rhenium single filaments. Multiple channel electron multipliers were used as detectors. Interferences were observed from molybdenum isotopes and were corrected for based on the (95)Mo count rate. Isotope ratios of zirconium were determined in ranges of 0.016-2.84 ((91)Zr/(90)Zr), 0.020-2.46 ((92)Zr/(90)Zr), 0.115-10.93 ((94)Zr/(90)Zr), and 0.004-5.70 ((96)Zr/(90)Zr). The respective relative uncertainties lay in the range of 0.03-4.2%. Typical relative uncertainties of tracer concentrations were 4%. AU - Greiter, M. AU - Höllriegl, V. AU - Oeh, U. C1 - 6444 C2 - 28698 SP - 1-8 TI - Method development for thermal ionization mass spectrometry in the frame of a biokinetic tracer study with enriched stable isotopes of zirconium. JO - Int. J. Mass Spectrom. VL - 304 IS - 1 PB - Elsevier PY - 2011 SN - 1387-3806 ER - TY - JOUR AB - Instruments used for basic studies in secondary ion mass spectrometry (SIMS) are usually not very well characterized in terms of important experimental parameters like the energy bandwidth and the origin of the energy scale. A proof-of-concept is presented which shows that in magnetic sector field mass spectrometers this kind of information can be obtained rather easily by determining the spectral features of ions generated by primary ion impact on a gas deliberately introduced in the extraction region above the sample. Owing to the negligible kinetic energy of the gas atoms, the measured energy spectrum exhibits a well-defined edge which corresponds to moving the energy bandpass through the gas–solid interface at the target surface. The energy resolution function can be derived as the derivative of the measured data. For high accuracy it is mandatory that the detected ions originate from a volume that is uniformly illuminated by the primary ion beam. The validity of the concept is demonstrated by evaluating recently published literature data. Even though the experiments were performed with a rather large bandwidth, shown to be 30.2 eV, the highly symmetric resolution function allowed the origin of the energy scale to be determined with an accuracy of ±0.2 eV. The potential of the approach needs to be explored in more detail by varying the relevant experimental parameters. AU - Wittmaack, K. C1 - 5608 C2 - 28536 SP - 65-69 TI - Accurate in situ calibration of the energy bandwidth and the zero-energy offset in SIMS analysis using magnetic sector field instruments. JO - Int. J. Mass Spectrom. VL - 300 IS - 1 PB - Elsevier PY - 2011 SN - 1387-3806 ER - TY - JOUR AB - A multidimensional statistical analysis of data obtained from breath gas measurements with Proton Transfer Reaction-Mass Spectrometry (PTR-MS) is proposed, based on a chemical-diffusion equilibrium approach. The proposed methodology is developed and demonstrated on the problem of detecting exposure of human beings to ionizing radiation. It could be applied to a general family of non-invasive, high-throughput, breath gas based detection strategies, like for instance a breath gas test for early diagnosis of lung cancer. AU - Fedrigo, M. AU - Hoeschen, C. AU - Oeh, U. C1 - 1872 C2 - 27375 SP - 13-20 TI - Multidimensional statistical analysis of PTR-MS breath samples: A test study on irradiation detection. JO - Int. J. Mass Spectrom. VL - 295 IS - 1-2 PB - Elsevier PY - 2010 SN - 1387-3806 ER - TY - JOUR AB - Diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea), a common herbicide from phenyl urea class, was investigated by studying the formation of several negative ions [M−H]− in the gas phase and the fragmentation behaviour of the thermodynamically most probably formed isomeric anions upon linear ion acceleration/collision experiments. The collision induced dissociation experiments (CID) were carried out in a hexapole–quadrupole–hexapole hybrid system coupled to 12 T magnet with infinity ICR cell for high resolution measurements. Two distinctive main pathways were observed in the MS/MS spectrum. Sustained off-resonance irradiation (SORI) experiments inside the ICR cell reinforce the fragmentation channels obtained from linear ion acceleration experiments. The fragmentation pathways were also completely investigated by the use of B3LYP/6-311+G(2d,p)//B3LYP/6-31+G(d) level of theory. Elimination of dimethylamine takes place in a two-step process, by which two successive 1,3 proton shifts occur. The second 1,3 proton shift is concerted with the departure of dimethylamine. The driving force for the (CH3)2NH elimination is the formation of isocyanate group. The formed primary product ion can further decompose to release HCl through a new transition state. A stable new aromatic product ion is formed with 10π electrons. Loss of C3H5NO neutral from another anionic isomer of the precursor ion was also observed and is characteristic for the amide terminal of the diamide functional group. A concerted mechanism is proposed, by which N–C bond breakage and cyclization of the eliminated neutral fragment C3H5NO takes place simultaneously to form 1-methyl-aziridin-2-one. AU - Kanawati, B. AU - Harir, M. AU - Schmitt-Kopplin, P. C1 - 1748 C2 - 26611 SP - 6-15 TI - Exploring rearrangements along the fragmentation pathways of diuron anion: A combined experimental and computational investigation. JO - Int. J. Mass Spectrom. VL - 288 IS - 1-3 PB - Elsevier PY - 2009 SN - 1387-3806 ER - TY - JOUR AB - PTR-MS is becoming a common method for the analysis of volatile organic compounds (VOCs) in human breath. Breath gas contains substantial and, particularly for bag samples, highly variable concentrations of water vapour (up to not, vert, similar6.3%) and carbon dioxide (up to not, vert, similar6.5%). The goal of this study was to investigate the effects of carbon dioxide on PTR-MS measurements; such effects can be expected in view of the already well known effects of water vapour. Carbon dioxide caused an increase of the pressure in the PTR-MS drift tube (not, vert, similar1% increase for 5% CO2), and this effect was used to assess the CO2 concentration of breath gas samples along the way with the analysis of VOCs. Carbon dioxide enhanced the concentration ratio of protonated water clusters (H3O+H2O) to protonated water (H3O+) in the drift tube. Using the observed increase, being not, vert, similar60% for 5% CO2, it is estimated that the mobility of water cluster ions in pure CO2 is almost 65% lower than in air. Carbon dioxide had a significant effect on the mass spectra of the main breath gas components methanol, ethanol, 1-propanol, 2-propanol, acetone, and isoprene. Carbon dioxide caused a small increase (<10% for 5% CO2) of the normalised main signals for the non-fragmenting molecules methanol and acetone. The increase can be much higher for the fragmenting VOCs (ethanol, propanol, and isoprene) and was, for 5% CO2, up to not, vert, similar60% for ethanol. This effect of CO2 on fragment patterns is mainly a consequence of the increased abundance of protonated water clusters, which undergo softer reactions with VOCs than the hydronium ions. Breath gas samples stored in Teflon bags lost not, vert, similar80% of CO2 during 3 days, the decrease of VOC signals, however, is mainly attributed to decreasing VOC concentrations and to the loss of humidity from the bags. AU - Keck, L. AU - Hoeschen, C. AU - Oeh, U. C1 - 1766 C2 - 25324 SP - 156-165 TI - Effects of carbon dioxide in breath gas on proton transfer reaction-mass spectrometry (PTR-MS) measurements. JO - Int. J. Mass Spectrom. VL - 270 IS - 3 PB - Elsevier PY - 2008 SN - 1387-3806 ER - TY - JOUR AB - During bombardment of solid samples with rare gas ions, charge-transfer events can convert reemitted rare gas atoms to positively charged ions. In analytical applications of secondary ion mass spectrometry (SIMS) this mechanism of ion formation is of considerable interest because, owing to their high ionisation potential, the ion fraction of sputtered rare gas atoms is very low. A quadrupole-based SIMS instrument was used to study details of the gas-phase ionisation process, notably the variation of the ion production rate as a function of the distance from the surface. The relevant information was derived from the apparent energy spectra of gas-phase generated (GPG) ions, observed during bombardment of a variety of elemental targets with Ne+, Ar+ and Kr+ beams at energies between 3 and 12 keV. Owing to the use of a secondary ion extraction field of low strength, gas-phase ionisation events could be separated by distance ? from the surface, with ? up to about 6 mm. The results were compared with a simple model that describes the ion production rate as the product of the gas-atom flow rate and the ionisation probability. The first factor is proportional to the primary ion current and the second proportional to the current density j0. Therefore, the intensity of GPG ions is not proportional to View the MathML source, as assumed previously. The mean ionisation probabilities of GPG ions (not, vert, similar10-5 at a moderate mean current density of not, vert, similar2 mA/cm2) were found to be higher by more than four orders of magnitude compared to ‘ordinary’ SIMS. In part, this favourable result can be attributed to the low energy of rare gas atom ejection (not, vert, similar0.1 eV). The experimental data suggest that the angular distributions of ejected rare gas atoms are strongly forward peaked. Presumably for this reason the yields of GPG ions observed with an amorphised target like silicon were distinctly higher than with polycrystalline metals. In the latter case, emission from unfavourably oriented microcrystals causes a large fraction of ejected gas atoms to escape from the interaction volume before ionisation can occur. Further enhancement in yield can be expected by the use of focussed primary ion beams with fairly uniform rather than Gaussian-like current density distributions. If the atomic number of the projectile is slightly lower than that of the target atom, as for Ne+ impact on Mg, Al and Si or Ar+ impact on Ti+, sizable or even high signals, independent of current density, were observed due to energetic multiply scattered ions. AU - Wittmaack, K. C1 - 573 C2 - 26331 SP - 24-33 TI - Gas-phase ionisation of sputtered rare gas atoms. JO - Int. J. Mass Spectrom. VL - 269 IS - 1-2 PB - Elsevier B.V. PY - 2008 SN - 1387-3806 ER - TY - JOUR AB - A corrected equation for the concentrations in the drift tube of a proton transfer reaction-mass spectrometer (PTR-MS) is presented which accounts for the different mobility of primary ions and protonated analyte previous termvolatilenext term organic compounds (VOCs). As a consequence, the calculation of VOC concentrations from the measured count rates requires as well a correction factor, equalling the ratio of (i) the mobility of the protonated analyte VOCs to (ii) the mobility of the gases used to determine the transmission efficiency. However, such data do essentially not exist for the relevant VOCs. Published mobility data for small inorganic ions suggest that the correction can be larger than 20% and hence be a significant contribution to the overall accuracy of calculated concentrations. The correction emphasises the need to calibrate the PTR-MS in order to determine VOC concentrations accurately. AU - Keck, L. AU - Oeh, U. AU - Hoeschen, C. C1 - 5871 C2 - 24489 SP - 92-95 TI - Corrected equation for the concentrations in the drift tube of a proton transfer reaction-mass spectrometer (PTR-MS). JO - Int. J. Mass Spectrom. VL - 264 IS - 1 PB - Elsevier PY - 2007 SN - 1387-3806 ER - TY - JOUR AB - An aerosol mass spectrometric set-up is presented comprising three different laser based techniques for on-line analysis of particles. The implemented methods are one-step laser desorption/ionisation (LDI), two-step laser desorption/photoionisation (LDPI) and thermal desorption/photoionisation (TDPI). Photoirmisation processes for the latter two methods are based on resonance enhanced multiphoton ionisation (REMPI), which is highly selective and sensitive for polyaromatic hydrocarbons (PAH). LDI is especially suitable for the detection of inorganic compounds and the determination of sum values such as elemental carbon content. Investigated samples were particles from spruce wood ash generated by an oxygen-controlled residential heating system and exhaust gases from a gasoline driven passenger car. In the positive LDI mass spectra several metal cations such as potassium and iron are detectable, whereas carbon clusters can be observed with the negative mode. With LD-REMPI and TD-REMPI various PAH such as phenanthrene and derivatives, pyrene, etc., become visible. In the wood ash samples relatively high yields of retene were found, which could be used as tracer compound for coniferous wood combustion. All three modes can be applied with only slight modifications of the instrument. Thus, it allows characterising single particles on a real time basis and, depending on the application, the most convenient technique can be selected. AU - Bente, M. AU - Adam, T. AU - Ferge, T. AU - Gallavardin, S. AU - Sklorz, M. AU - Streibel, T. AU - Zimmermann, R. C1 - 3562 C2 - 24083 SP - 86-94 TI - An on-line aerosol laser mass spectrometer with three, easily interchangeable laser based ionisation methods for characterisation of inorganic and aromatic compounds on particles. JO - Int. J. Mass Spectrom. VL - 258 IS - 1-3 PY - 2006 SN - 1387-3806 ER - TY - JOUR AU - Schneider, J.* AU - Weimer, S.* AU - Drewnick, F.* AU - Borrmann, S.* AU - Helas, G.* AU - Gwaze, P.* AU - Schmid, O. AU - Andreae, M.O.* AU - Kirchner, U.* C1 - 5486 C2 - 24118 SP - 37-49 TI - Mass spectrometric analysis and aerodynamic properties of various types of combustion-related aerosol particles. JO - Int. J. Mass Spectrom. VL - 258 PY - 2006 SN - 1387-3806 ER - TY - JOUR AU - Szymczak, W. AU - Menzel, N. AU - Kreyling, W.G. AU - Wittmaack, K. C1 - 5343 C2 - 23906 SP - 70-84 TI - TOF-SIMS characterisation of spark-generated nanoparticles made from pairs of Ir-Ir and Ir-C electrodes. JO - Int. J. Mass Spectrom. VL - 254 PY - 2006 SN - 1387-3806 ER - TY - JOUR AU - Bernhardt, P. AU - Friedland, W. AU - Jacob, P. AU - Paretzke, H.G. C1 - 9728 C2 - 20803 SP - 579-597 TI - Modeling of ultrasoft X-ray induced DNA damage using structured higher order DNA targets. JO - Int. J. Mass Spectrom. VL - 223-224 PY - 2003 SN - 1387-3806 ER - TY - JOUR AU - Bernhardt, Ph. AU - Paretzke, H.G. C1 - 10129 C2 - 20804 SP - 599-611 TI - Calculation of electron impact ionization cross sections of DNA using the Deutsch-Märk and Binary-Encounter-Bethe formalisms. JO - Int. J. Mass Spectrom. VL - 223-224 PY - 2003 SN - 1387-3806 ER - TY - JOUR AB - In secondary ion mass spectrometry (SIMS) studies it was found that analysed ions emerging from a quadrupole filter may be accompanied by a surprisingly large number of tertiary ions of the opposite charge. In the mass spectrum the tertiary ions show up at the high-mass edge of the stability diagram (x-stability limit). The peak intensity ratios of tertiary to secondary ions, i- / I+ and i+ / I-, observed with mass-filtered atomic and molecular ions, range from about 10-5 to 4 × 10-3. The effect was studied in detail as a function of the d.c.-to-a.c. voltage ratio, the orientation of the d.c. field, the frequency of operation, the ion energy, the beam current and the chamber pressure. The experimental data are consistent with the idea that most of the tertiary ions are generated under the impact of radially accelerated ions striking the quadrupole rods. Only those tertiary ions which are produced near the exit of the quadrupole have a chance to get to the detector. In the case of very light secondary ions such as H+ charge changing collisions may be largely responsible for the generation of ions of the opposite charge state. AU - Wittmaack, K. C1 - 42679 C2 - 36452 SP - 197-209 TI - Production of ions of the opposite charge in mass analysis using a quadrupole filter. JO - Int. J. Mass Spectrom. VL - 69 IS - 2 PY - 1986 SN - 1387-3806 ER - TY - JOUR AB - A time-of-flight mass spectrometer (laser-micro-mass-analyzer LAMMA 500) was modified to allow the simultaneous detection of ions as well as neutral species originating from the metastable decay. The influence of sample preparation and laser irradiance on the mass spectra was examined and significant differences in the decompositions of acid and salt samples were found. Some initial measurements of simple aromatic carboxylic acids and their salts gave some new information about fragmentation and metastable decay after short pulse UV laser desorption. AU - Rosmarinowsky, J. AU - Karaś, M.* AU - Hillenkamp, F.* C1 - 42728 C2 - 36381 SP - 109-119 TI - Metastable decay of laser-desorbed ions from aromatic organic compounds. JO - Int. J. Mass Spectrom. VL - 67 IS - 2 PY - 1985 SN - 1387-3806 ER - TY - JOUR AU - Éloy, J.F.* AU - Leleu, M.* AU - Unsöld, E. C1 - 42670 C2 - 38307 SP - 39-42 TI - Geological applications of the laser probe mass spectrometer (L.P.M.S.II). JO - Int. J. Mass Spectrom. VL - 47 IS - C PY - 1983 SN - 1387-3806 ER - TY - JOUR AB - A simple secondary ion mass spectrometer has been developed to allow trace analysis at impurity concentrations down to the parts per billion range. The spectrometer consists of an aperture bounded plate capacitor followed by a quadrupole mass flter with an off-axis detector. This arrangement allows suppression of sputtered neutrals and high energy sputtered or backscattered ions which otherwise produce a high background intensity of more than 1% of the target peak intensity in our set-up. After optimization of the geometry of the plate capacitor an intensity ratio of peak to background of 2 × 108 could be obtained for an aluminium specimen. The capability of the arrangement is demonstrated by trace analysis of boron in silicon. The process of background formation by neutrals and high energy ions is studied and discussed. AU - Wittmaack, K. AU - Maul, J.L. AU - Schulz, F. C1 - 42642 C2 - 35394 SP - 23-35 TI - A low background secondary ion mass spectrometer with quadrupole analyser. JO - Int. J. Mass Spectrom. VL - 11 IS - 1 PY - 1973 SN - 1387-3806 ER -