Publications (70)103 Total impact
- [Show abstract] [Hide abstract] ABSTRACT: An electron emitter as soft atmospheric pressure chemical ionization source is presented, which operates at inner pressures of the device in the medium vacuum range (>10-3 hPa). Conventional non-radioactive electron emitters require high vacuum (<10-6 hPa) to prevent electrical spark-overs. The emitter presented here contains structural modifications of an existing setup, which inhibits electrical breakdowns up to 10-2 hPa at 8 kV acceleration voltage. The increased inner pressure reduces the ionization efficiency till 10-3 hPa - achievable without a turbo-molecular pump - by 2 % compared to high vacuum conditions. This can be compensated with an increase of the electron source output. The functionality of this ion source is demonstrated with mass spectrometric and ion mobility measurements of Acetone, Eucalyptol and Diisopropyl methanephosphonate. Additional mass spectrometric measurements of 20 different organic compounds demonstrate the soft characteristics of this ionization source.
- [Show abstract] [Hide abstract] ABSTRACT: Occupational exposure to sevoflurane has the potential to cause health damage in hospital personnel. Workplace contamination with the substance mostly is assessed by using photoacoustic infrared spectrometry with detection limits of 10 ppbv. Multi-capillary column-ion mobility spectrometry (MCC-IMS) could be an alternative technology for the quantification of sevoflurane in the room air and could be even more accurate because of potentially lower detection limits. The aim of this study was to test the hypothesis that MCC-IMS is able to detect and monitor very low concentrations of sevoflurane (<10 ppbv) and to evaluate the exposure of hospital personnel to sevoflurane during paediatric anaesthesia and in the post anaesthesia care unit (PACU). A MCC-IMS device was calibrated to several concentrations of sevoflurane and limits of detection (LOD) and quantification (LOQ) were calculated. Sevoflurane exposure of hospital personnel was measured at two anaesthesia workplaces and time-weighted average (TWA) values were calculated. The LOD was 0.0068 ppbv and the LOQ was 0.0189 ppbv. During paediatric anaesthesia the mean sevoflurane concentration was 46.9 ppbv (8.0 - 314.7 ppbv) with TWA values between 5.8 and 45.7 ppbv. In the PACU the mean sevoflurane concentration was 27.9 ppbv (8.0 - 170.2 ppbv) and TWA values reached from 8.3 to 45.1 ppbv. MCC-IMS shows a significantly lower LOD and LOQ than comparable methods. It is a reliable technology for monitoring sevoflurane concentrations at anaesthesia workplaces and has a particular strength in quantifying low-level contaminations of sevoflurane. The exposure of the personnel working in these areas did not exceed recommended limits and therefore adverse health effects are unlikely.
- [Show abstract] [Hide abstract] ABSTRACT: Abstract— Border security is one of the key challenges to be taken up by Europe in the following years. In particular, the deployment of practical efficient means to detect hidden persons and illegal substances at border crossing points is instrumental in avoiding terrorism, human trafficking or smuggling. This study presents the concept of an “orthogonal” approach to the identification of gas traces identified as pertinent targets for illicit substances (drugs and explosives) as well as for human presence. The techniques employed to perform the analysis are based on completely different physical principles; these are the Mid-Infrared photo-acoustic spectroscopy (MIR-PAS - demonstration of a novel widely tunable integrated MIR source coupled with a miniature photo-acoustic cell) and the Ion mobility spectrometry (IMS) using a non radio-active ionization source. Definition of the pertinent compounds and their “spectral signature” (characterized with recording of the vapour phase IR properties via GC-FTIR and GC-MS), lead to a database of the target substances; the IR wavelengths were selected based on the individual target. For the case of human presence, volatile fatty acids (VFA) present in human sweat identified as ideal targets for remote detection of hidden persons; for example some VFAs are human specific, such as HMHA and 3MHA. The aforementioned VFAs are also active in the MIR range. Similarly for the case of the illicit drugs targeting has been based on their emitted VOCs depending on the type of substance (e.g. alkaloid drugs associated with their volatile degradation products etc); during this study, characterization of the cannabis markers lead to the identification of a new marker (under revision for European patent). For explosives substances volatile taggants are mainly associated with VOCs available during their preparation. In total 58 volatile organic compounds (VOCs) were identified in this study as candidates for the detection of Humans (31), Illegal Drugs (19), and Explosives (13). The aforementioned spectral database has been employed for algorithm selection and training; the algorithms used were the Support Vector Machines (SVM), Partial Least Squares – Discrimant Analysis (PLS – DA) and the k – Nearest Neighbour (KNN); the results are very promising reaching levels of matching during training up to 98%. These algorithms will fuse the data collected and analysed by the two powerful techniques selected as the components of this « orthogonal » approach to the detection of the aforementioned gas traces. Target specific cavitand receptors were developed for the pre-concentrator procedure that increase the concentration of the gas trace in quest. During this work, improvement to the pre-concentration configuration has reduced the required time for the pre-concentration procedure significantly (10s of seconds compared to several minutes); this is part of the novelties developed during this study. IMS studies for detection of human presence has shown very promising results, recording levels of human specific gas traces after 15 minutes of a human present in an area of 50m3. This is very important considering that in most cases the people illegaly immigrating are confined in much smaller spaces and for very much longer periods (most of the times are more than one person too) which leads to increased concentration and abundance of the related VOCs hence, the instrument will definetely perform better. A miniaturized MIR-PAS has been developed supported by an array of DFB-QCLs that allows for this instrument to be a portable solution for operators at border points, assisting their daily activities and increase their performance. This is a powerful and promising tool to detect a very wide range of volatile organic compounds (VOCs). Keywords—Border security, Orthogonal Technologies, IMS, MIRPAS, Human Detection, Illicit Drugs, Explosives, Olfactory, Mobile Instrument
- [Show abstract] [Hide abstract] ABSTRACT: The design, development, and validation of a dynamic vapor generator are presented. The generator simulates human scent (odor) emissions from trapped victims in the voids of collapsed buildings. The validation of the device was carried out using a reference detector: a quadrupole mass spectrometer equipped with a pulsed sampling (PS-MS) system. A series of experiments were conducted for evaluating the simulator's performance, defining types and weights of different factors, and proposing further optimization of the device. The developed device enabled the production of stable and transient odor profiles in a controllable and reproducible way (relative standard deviation, RSD < 11%) at ppbv to low ppmv concentrations and allowed emission durations up to 30 min. Moreover, the factors affecting its optimum performance (i.e., evaporation chamber temperature, air flow rate through the mixing chamber, air flow rate through the evaporation chamber, and type of compound) were evaluated through an analysis of variance (ANOVA) tool revealing the next steps toward optimizing the generator. The developed simulator, potentially, can also serve the need for calibrating and evaluating the performance of analytical devices (e.g., gas chromatographers, ion mobility spectrometers, mass spectrometers, sensors, e-noses) in the field. Furthermore, it can contribute in better training of urban search and rescue (USaR) canines.
- [Show abstract] [Hide abstract] ABSTRACT: Ion mobility spectrometry (IMS) is a well-known analytical method for the detection of CWAs and explosives since many years. Coupling IMS to GC pre-separation, new application fields in medicine and biology could be opened, dealing with complex and humid mixtures. However, identification of unknowns in such a complex sample is challenging and can only be achieved by parallel GC/MS analysis, thus obtaining a proposal for the responsible compound for validation via reference substances by GC/IMS again. The available adsorption tools for such accompanying GC/MS analysis have their particular drawbacks (e.g. problematic quantification for SPME, high sample volumes for adsorption tubes). Therefore miniaturised adsorption needles (NeedleTrap) were applied to both GC/IMS and GC/MS for validation of their reproducibility. It could be demonstrated that the needles can even be used for appropriate quantification when the adsorbent and the sample volume are adapted properly to the concentration range, the compounds of interest and humidity of the sample. The method is very flexible with regard to the concentration range by variation of the sample volume (e.g. 20 mL for pptV, 10 mL for lower ppbV or 1 mL for ppmV) and with regard to the compounds of interest by application of common adsorption materials optimised for the relevant substance group. Such materials are available commercially in a broad variability. Therefore, the miniaturised adsorption needles are a helpful complementary sampling method for any GC/MS or GC/IMS investigations.
- [Show abstract] [Hide abstract] ABSTRACT: The project “Second Generation Locator for Urban Search and Rescue” or simply SGL, is an EC funded research project, which aims at the support of rescue people during the search of entrapped people or dead bodies in collapsed structures. One part of the project is the establishment of unattended, wireless monitoring devices, that are able to raise alarms in case of detected signs of life, danger, or death. This article gives a short overview of the systems structure, the concepts of sensor fusion, and the use of fuzzy logic as the central decision making mechanism.
- [Show abstract] [Hide abstract] ABSTRACT: In this paper we propose a novel peak detection algorithm for 2-dimensional analytical data. The proposed algorithm utilizes the properties of the second derivative and curvature of (regular) surfaces to perform peak detection. Raw data used in this study for performance demonstration were obtained by a hyphenated system called gas-chromatographic column ion mobility spectrometer (GC-IMS). GC-IMS is a two stage technique for separation of gas-phased (organic) compounds. Despite the good performance of the MCC-IMS separation in general, there are still unsatisfactory cases where the substances overlap and the recorded signals nearly merge. Frequently used peak detection algorithm for 2-dimensional data, like the watershed algorithm, do not perform well in those cases. Preliminary empirical results show good peak detection performance of the proposed algorithm. Furthermore the results indicate that the proposed algorithm is capable to solve the problem of peak detection even in cases of strong peak overlapping. © 2013 Springer-Verlag Berlin Heidelberg. All rights are reserved.
- [Show abstract] [Hide abstract] ABSTRACT: For the comprehensive simulation of ion trajectories including reactive collisions at elevated pressure conditions, a chemical reaction simulation (RS) extension to the popular SIMION software package was developed, which is based on the Monte Carlo statistical approach. The RS extension is of particular interest to SIMION users who wish to simulate ion trajectories in collision dominated environments such as atmospheric pressure ion sources, ion guides (e.g., funnels, transfer multi poles), chemical reaction chambers (e.g., proton transfer tubes), and/or ion mobility analyzers. It is well known that ion molecule reaction rate constants frequently reach or exceed the collision limit obtained from kinetic gas theory. Thus with a typical dwell time of ions within the above mentioned devices in the ms range, chemical transformation reactions are likely to occur. In other words, individual ions change critical parameters such as mass, mobility, and chemical reactivity en passage to the analyzer, which naturally strongly affects their trajectories. The RS method simulates elementary reaction events of individual ions reflecting the behavior of a large ensemble by a representative set of simulated reacting particles. The simulation of the proton bound water cluster reactant ion peak (RIP) in ion mobility spectrometry (IMS) was chosen as a benchmark problem. For this purpose, the RIP was experimentally determined as a function of the background water concentration present in the IMS drift tube. It is shown that simulation and experimental data are in very good agreement, demonstrating the validity of the method.
- [Show abstract] [Hide abstract] ABSTRACT: For the first time, ion mobility spectrometry coupled to rapid gas-chromatography using multi-capillary columns was applied for the development of a pattern of signs of life for the localisation of entrapped victims after disaster events (e.g. earth quake, terroristic attack). During a simulation experiment with entrapped volunteers, 12 human metabolites could be detected in the air of the void with sufficient sensitivity to enable a valid decision on the presence of a living person. Using a basic normalised summation of the measured concentrations, all volunteers involved in the particular experiments could be recognised only few minutes after they entered the simulation void. The analysis time is less than 3 minutes. An additional independent validation experiment enabled the recognition of a person in a room of ~25 m³ after approx. 30 minutes with high enough sensitivity to detect even short leaving of the room. It is doubtless that further work has to be done on analysis time and weight of the equipment but also on the validation during real disaster events. However, the enormous potential of the method as significantly helpful tool for search and rescue operations in addition to trained canines could be demonstrated.
Article: Volatile Organic Compounds in Uremia[Show abstract] [Hide abstract] ABSTRACT: Although "uremic fetor" has long been felt to be diagnostic of renal failure, the compounds exhaled in uremia remain largely unknown so far. The present work investigates whether breath analysis by ion mobility spectrometry can be used for the identification of volatile organic compounds retained in uremia. Breath analysis was performed in 28 adults with an eGFR ≥60 ml/min per 1.73 m(2), 26 adults with chronic renal failure corresponding to an eGFR of 10-59 ml/min per 1.73 m(2), and 28 adults with end-stage renal disease (ESRD) before and after a hemodialysis session. Breath analysis was performed by ion mobility spectrometryafter gas-chromatographic preseparation. Identification of the compounds of interest was performed by thermal desorption gas chromatography/mass spectrometry. Breath analyses revealed significant differences in the spectra of patients with and without renal failure. Thirteen compounds were chosen for further evaluation. Some compounds including hydroxyacetone, 3-hydroxy-2-butanone and ammonia accumulated with decreasing renal function and were eliminated by dialysis. The concentrations of these compounds allowed a significant differentiation between healthy, chronic renal failure with an eGFR of 10-59 ml/min, and ESRD (p<0.05 each). Other compounds including 4-heptanal, 4-heptanone, and 2-heptanone preferentially or exclusively occurred in patients undergoing hemodialysis. Impairment of renal function induces a characteristic fingerprint of volatile compounds in the breath. The technique of ion mobility spectrometry can be used for the identification of lipophilic uremic retention molecules.
- [Show abstract] [Hide abstract] ABSTRACT: Presently, 2 to 4 days elapse between sampling at infection suspicion and result of microbial diagnostics. This delay for the identification of pathogens causes quite often a late and/or inappropriate initiation of therapy for patients suffering from infections. Bad outcome and high hospitalization costs are the consequences of these currently existing limited pathogen identification possibilities. For this reason, we aimed to apply the innovative method multi-capillary column-ion mobility spectrometry (MCC-IMS) for a fast identification of human pathogenic bacteria by determination of their characteristic volatile metabolomes. We determined volatile organic compound (VOC) patterns in headspace of 15 human pathogenic bacteria, which were grown for 24 h on Columbia blood agar plates. Besides MCC-IMS determination, we also used thermal desorption-gas chromatography-mass spectrometry measurements to confirm and evaluate obtained MCC-IMS data and if possible to assign volatile compounds to unknown MCC-IMS signals. Up to 21 specific signals have been determined by MCC-IMS for Proteus mirabilis possessing the most VOCs of all investigated strains. Of particular importance is the result that all investigated strains showed different VOC patterns by MCC-IMS using positive and negative ion mode for every single strain. Thus, the discrimination of investigated bacteria is possible by detection of their volatile organic compounds in the chosen experimental setup with the fast and cost-effective method MCC-IMS. In a hospital routine, this method could enable the identification of pathogens already after 24 h with the consequence that a specific therapy could be initiated significantly earlier.
Article: ÌThe Trapped Human Experimentî[Show abstract] [Hide abstract] ABSTRACT: This experiment observed the evolution of metabolite plumes from a human trapped in a simulation of a collapsed building. Ten participants took it in turns over five days to lie in a simulation of a collapsed building and eight of them completed the 6 h protocol while their breath, sweat and skin metabolites were passed through a simulation of a collapsed glass-clad reinforced-concrete building. Safety, welfare and environmental parameters were monitored continuously, and active adsorbent sampling for thermal desorption GC-MS, on-line and embedded CO, CO(2) and O(2) monitoring, aspirating ion mobility spectrometry with integrated semiconductor gas sensors, direct injection GC-ion mobility spectrometry, active sampling thermal desorption GC-differential mobility spectrometry and a prototype remote early detection system for survivor location were used to monitor the evolution of the metabolite plumes that were generated. Oxygen levels within the void simulator were allowed to fall no lower than 19.1% (v). Concurrent levels of carbon dioxide built up to an average level of 1.6% (v) in the breathing zone of the participants. Temperature, humidity, carbon dioxide levels and the physiological measurements were consistent with a reproducible methodology that enabled the metabolite plumes to be sampled and characterized from the different parts of the experiment. Welfare and safety data were satisfactory with pulse rates, blood pressures and oxygenation, all within levels consistent with healthy adults. Up to 12 in-test welfare assessments per participant and a six-week follow-up Stanford Acute Stress Response Questionnaire indicated that the researchers and participants did not experience any adverse effects from their involvement in the study. Preliminary observations confirmed that CO(2), NH(3) and acetone were effective markers for trapped humans, although interactions with water absorbed in building debris needed further study. An unexpected observation from the NH(3) channel was the suppression of NH(3) during those periods when the participants slept, and this will be the subject of further study, as will be the detailed analysis of the casualty detection data obtained from the seven instruments used.
- [Show abstract] [Hide abstract] ABSTRACT: A multi-capillary column ion mobility spectrometer (MCC/IMS) was developed to provide a method for the noninvasive diagnosis of lung diseases. The possibility of measuring the exhaled breath of mice was evaluated previously. The aim of the present study was to reveal whether mice affected by airway inflammation can be identified via MCC/IMS. Ten mice were sensitized and challenged with ovalbumin to induce allergic airway inflammation. The breath and volatile compounds of bronchoalveolar lavage fluid (BALF) were measured by MCC/IMS. Furthermore, histamine, nitric oxide, and arachidonic acid were determined as inflammatory markers in vitro. Six volatile molecules were found in the BALF headspace at a significantly higher concentration in mice with airway inflammation compared with healthy animals. The concentration of substances correlated with the numbers of infiltrating eosinophilic granulocytes. However, substances showing a significantly different concentration in the BALF headspace were not found to be different in exhaled breath. Histamine and nitric oxide were identified by MCC/IMS in vitro but not in the BALF headspace or exhaled breath. Airway inflammation in mice is detectable by the analysis of the BALF headspace via MCC/IMS. Molecules detected in the BALF headspace of asthmatic mice at a higher concentration than in healthy animals may originate from oxidative stress induced by airway inflammation. As already described for humans, we found no correlation between the biomarker concentration in the BALF and the breath of mice. We suggest using the model described here to gain deeper insights into this discrepancy.
- [Show abstract] [Hide abstract] ABSTRACT: In nowadays life science projects, sharing data and data interpretation is becoming increasingly important. This considerably calls for novel information technology approaches, which enable the integration of expert knowledge from different disciplines in combination with advanced data analysis facilities in a collaborative manner. Since the recent development of web technologies offers scientific communities new ways for cooperation and communication, we propose a fully web-based software approach for the collaborative analysis of bioimage data and demonstrate the applicability of Web2.0 techniques to ion mobility spectrometry image data. Our approach allows collaborating experts to easily share, explore and discuss complex image data without any installation of software packages. Scientists only need a username and a password to get access to our system and can directly start exploring and analyzing their data.
- [Show abstract] [Hide abstract] ABSTRACT: Volatile metabolites of Aspergillus fumigatus and Candida species can be detected by gas chromatography/mass spectrometry (GC/MS). A multi-capillary column - ion mobility spectrometer (MCC-IMS) was used in this study to assess volatile organic compounds (VOCs) in the headspace above A. fumigatus and the four Candida species Candida albicans, Candida parapsilosis, Candida glabrata and Candida tropicalis in an innovative approach, validated for A. fumigatus and C. albicans by GC/MS analyses. For the detection of VOCs, a special stainless steel measurement chamber for the microbial cultures was used. The gas outlet was either attached to MCC-IMS or to adsorption tubes (Tenax GR) for GC/MS measurements. Isoamyl alcohol, cyclohexanone, 3-octanone and phenethylalcohol can be described as discriminating substances by means of GC/MS. With MCC-IMS, the results for 3-octanone and phenethylalcohol are concordant and additionally to GC/MS, ethanol and two further compounds (p_0642_1/p_683_1 and p_705_3) can be described. Isoamyl alcohol and cyclohexanone were not properly detectable with MCC-IMS. The major advantage of the MCC-IMS system is the feasibility of rapid analysis of complex gas mixtures without pre-concentration or preparation of samples and regardless of water vapour content in an online setup. Discrimination of fungi on genus level of the investigated germs by volatile metabolic profile and therefore detection of VOC is feasible. However, a further discrimination on species level for Candida species was not possible.
- [Show abstract] [Hide abstract] ABSTRACT: In the past decade, Ion Mobility Spectrometry has established a very strong foot hold in medical and biol. applications due to its numerous advantages including sensitivity, ruggedness and reproducibility. During the anal. of complex samples such as human breath, it is very probable that two or more analytes form peak clusters due to similar drift times and pre-sepn. times, thus hindering the identification of the analytes. Furthermore, such overlapping of signal makes quantification very difficult or even impossible. Resolving these peak clusters is important to enable proper identification and quantification of analytes detected for diagnosis. Hence, we designed a drift tube with variable length for investigating the influence of varying drift lengths and elec. field on resoln. Peak cluster formations usually seen between acetone and the reactant ion peak, between the dimer peaks of 2-Heptanone and 4-Heptanone have been resolved with the new drift tube after optimization. These novel drift tubes could easily negate the peak clusters often encountered when complex medical and biol. samples are measured with the ion mobility spectrometer. Furthermore, the fact that these drift tubes can be altered in length thereby providing a wide range of elec. fields (from 50 to 3300 V.cm-1), opens up new research options in ion motions in an elec. field. [on SciFinder(R)]
- [Show abstract] [Hide abstract] ABSTRACT: The major uncertainty related to ion mobility spectrometry is the lack of knowledge about the characteristics of the ions detected. When using a radioactive atmospheric pressure ionisation source (e.g. 63Ni), from theory proton bound water clusters are expected as reactant ions. When analyte ions occur, proton transfer should lead to proton-bound monomer and dimer ions. To increase the knowledge about those ionisation processes in an ion mobility spectrometer (IMS), a ß-radiation ionisation source was coupled to a mass spectrometer (MS) and an identical one to an IMS. Exemplarily, acetone, limonene and 2- and 5-nonanone were introduced into both instruments in varying concentrations. By correlating the MS and IMS spectra, conclusions about the identities of the ions detected by IMS could be drawn. Proton-bound monomer, dimer and even trimer ions (MH+, 2MH+, 3MH+) could be observed in the MS spectra for acetone and 5-nonanone and could be assigned to the related signals detected by IMS. The oligomers could be expected from theory for increasing concentration. Limonene and 2-nonanone yielded in a variety of different ions and fragments indicating complex gas phase ion chemistry. Those findings on the obviously different behaviour of different analytes require further research focussed on the ion chemistry in IMS including the comparison of different ionisation sources. KeywordsIon mobility spectrometry-Mass spectrometry-Atmospheric pressure ionisation-Acetone-Limonene-Cluster ions-Oligomers
Leibniz-Institut für Analytische WissenschaftenDortmund, North Rhine-Westphalia, Germany