The Experts below are selected from a list of 96474 Experts worldwide ranked by ideXlab platform
T D Mark - One of the best experts on this subject based on the ideXlab platform.
-
proton transfer reaction Mass Spectrometry for the study of the production of volatile compounds by bakery yeast starters
Journal of Mass Spectrometry, 2014Co-Authors: Salim Makhoul, Eugenio Aprea, Andrea Romano, Flavia Gasperi, T D Mark, Luca Cappellin, Vittorio Capozzi, Giuseppe Spano, Elisabetta Benozzi, Hanna ElnakatAbstract:The aromatic impact of bakery yeast starters is currently receiving considerable attention. The flavor characteristics of thedough and the finished products are usually evaluated by gas chromatography and sensory analysis. The limit of both tech-niques resides in their low-throughput character. In the present work, Proton-Transfer-Reaction Mass Spectrometry (PTR-MS),coupled to a time-of-flight Mass analyzer, was employed, for the first time, to measure the volatile fractions of dough andbread, and to monitor Saccharomyces cerevisiae volatile production in a fermented food matrix. Leavening was performed onsmall-scale (1g) dough samples inoculated with different commercial yeast strains. The leavened doughs were then baked,and volatile profiles were determined during leavening and after baking. The experimental setup included a multifunctionalautosampler, which permitted the follow-up of the leavening process on a small scale with a typical throughput of 500 distinctdata points in 16h. The system allowed to pinpoint differences between starter yeast strains in terms of volatile emissionkinetics, with repercussions on the final product (i.e. the corresponding micro-loaves). This work demonstrates the applicabilityof PTR-MS for the study of volatile organic compound production during bread-making, for the automated and online real-timemonitoring of the leavening process, and for the characterization and selection of bakery yeast starters in view of theirproduction of volatile compounds. Copyright © 2014 John Wiley & Sons, Ltd.Keywords: bakery; PTR-MS; leavening; yeast; VOCs
-
sulfides chemical ionization induced fragmentation studied with proton transfer reaction Mass Spectrometry and density functional calculations
Journal of Mass Spectrometry, 2013Co-Authors: Erna Schuhfried, Eugenio Aprea, Flavia Gasperi, T D Mark, Michael Probst, Jumras Limtrakul, Sippakorn Wannakao, Luca Cappellin, Franco BiasioliAbstract:We report the energy-dependent fragmentation patterns upon protonation of eight sulfides (organosulfur compounds) in Proton Transfer Reaction-Mass Spectrometry (PTR-MS). Studies were carried out, both, experimentally with PTR-MS, and with theoretical quantum-chemical methods. Charge retention usually occurred at the sulfur-containing fragment for short chain sulfides. An exception to this is found in the unsaturated monosulfide allylmethyl sulfide (AMS), which preferentially fragmented to a carbo-cation at m/z 41, C3H5+. Quantum chemical calculations (DFT with the M062X functional 6-31G(d,p) basis sets) for the fragmentation reaction pathways of AMS indicated that the most stable protonated AMS cation at m/z 89 is a protonated (cyclic) thiirane, and that the fragmentation reaction pathways of AMS in the drift tube are kinetically controlled. The protonated parent ion MH+ is the predominant product in PTR-MS, except for diethyl disulfide at high collisional energies. The saturated monosulfides R-S-R’ (with R
-
proton transfer reaction Mass Spectrometry and the unambiguous real time detection of 2 4 6 trinitrotoluene
Analytical Chemistry, 2012Co-Authors: Philipp Sulzer, T D Mark, Simone Jürschik, K Becker, Fredrik Petersson, Bishu Agarwal, David W Perry, P Watts, C A MayhewAbstract:Fears of terrorist attacks have led to the development of various technologies for the real-time detection of explosives, but all suffer from potential ambiguities in the assignment of threat agents. Using proton transfer reaction Mass Spectrometry (PTR-MS), an unusual bias dependence in the detection sensitivity of 2,4,6 trinitrotoluene (TNT) on the reduced electric field (E/N) has been observed. For protonated TNT, rather than decreasing signal intensity with increasing E/N, which is the more usual sensitivity pattern observed in PTR-MS studies, an anomalous behavior is first observed, whereby the signal intensity initially rises with increasing E/N. We relate this to unexpected ion–molecule chemistry based upon comparisons of measurements taken with related nitroaromatic compounds (1,3,5 trinitrobenzene, 1,3 dinitrobenzene, and 2,4 dinitrotoluene) and electronic structure calculations. This dependence provides an easily measurable signature that can be used to provide a rapid highly selective analytica...
-
real time trace detection and identification of chemical warfare agent simulants using recent advances in proton transfer reaction time of flight Mass Spectrometry
Rapid Communications in Mass Spectrometry, 2009Co-Authors: Fredrik Petersson, Alfons Jordan, C A Mayhew, Philipp Sulzer, P Watts, Lukas Mark, T D MarkAbstract:This work demonstrates for the first time the potential of using recent developments in proton transfer reaction Mass Spectrometry for the rapid detection and identification of chemical warfare agents (CWAs) in real-time. A high-resolution (m/Δm up to 8000) and high-sensitivity (∼50 cps/ppbv) proton transfer reaction time-of-flight Mass spectrometer (PTR-TOF 8000 from Ionicon Analytik GmBH) has been successfully used to detect a number of CWA simulants at room temperature; namely dimethyl methylphosphonate, diethyl methylphosphonate, diisopropyl methylphosphonate, dipropylene glycol monomethyl ether and 2-chloroethyl ethyl sulfide. Importantly, we demonstrate in this paper the potential to identify CWAs with a high level of confidence in complex chemical environments, where multiple threat agents and interferents could also be present in trace amounts, thereby reducing the risk of false positives. Instantaneous detection and identification of trace quantities of chemical threats using proton transfer reaction Mass Spectrometry could form the basis for a timely warning system capability with greater precision and accuracy than is currently provided by existing analytical technologies. Copyright © 2009 John Wiley & Sons, Ltd.
-
on line monitoring of microbial volatile metabolites by proton transfer reaction Mass Spectrometry
Applied and Environmental Microbiology, 2008Co-Authors: Michael Bunge, A Hansel, Armin Wisthaler, Tomas Mikoviny, Nooshin Araghipour, J Dunkl, R Schnitzhofer, Franz Schinner, Rosa Margesin, T D MarkAbstract:A method for analysis of volatile organic compounds (VOCs) from microbial cultures was established using proton transfer reaction-Mass Spectrometry (PTR-MS). A newly developed sampling system was coupled to a PTR-MS instrument to allow on-line monitoring of VOCs in the dynamic headspaces of microbial cultures. The novel PTR-MS method was evaluated for four reference organisms: Escherichia coli, Shigella flexneri, Salmonella enterica, and Candida tropicalis. Headspace VOCs in sampling bottles containing actively growing cultures and uninoculated culture medium controls were sequentially analyzed by PTR-MS. Characteristic marker ions were found for certain microbial cultures: C. tropicalis could be identified by several unique markers compared with the other three organisms, and E. coli and S. enterica were distinguishable from each other and from S. flexneri by specific marker ions, demonstrating the potential of this method to differentiate between even closely related microorganisms. Although the temporal profiles of some VOCs were similar to the growth dynamics of the microbial cultures, most VOCs showed a different temporal profile, characterized by constant or decreasing VOC levels or by single or multiple peaks over 24 h of incubation. These findings strongly indicate that the temporal evolution of VOC emissions during growth must be considered if characterization or differentiation based on microbial VOC emissions is attempted. Our study may help to establish the analysis of VOCs by on-line PTR-MS as a routine method in microbiology and as a tool for monitoring environmental and biotechnological processes.
Joost De Gouw - One of the best experts on this subject based on the ideXlab platform.
-
Proton-Transfer-Reaction Mass Spectrometry: Applications in Atmospheric Sciences
Chemical reviews, 2017Co-Authors: Bin Yuan, Carsten Warneke, Abigail R. Koss, Matthew M. Coggon, Kanako Sekimoto, Joost De GouwAbstract:Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) has been widely used to study the emissions, distributions, and chemical evolution of volatile organic compounds (VOCs) in the atmosphere. The applications of PTR-MS have greatly promoted understanding of VOC sources and their roles in air-quality issues. In the past two decades, many new Mass spectrometric techniques have been applied in PTR-MS instruments, and the performance of PTR-MS has improved significantly. This Review summarizes these developments and recent applications of PTR-MS in the atmospheric sciences. We discuss the latest instrument development and characterization work on PTR-MS instruments, including the use of time-of-flight Mass analyzers and new types of ion guiding interfaces. Here we review what has been learned about the specificity of different product ion signals for important atmospheric VOCs. We present some of the recent highlights of VOC research using PTR-MS including new observations in urban air, bioMass-burning plumes,...
-
measurements of volatile organic compounds in the earth s atmosphere using proton transfer reaction Mass Spectrometry
Mass Spectrometry Reviews, 2007Co-Authors: Joost De Gouw, Carsten WarnekeAbstract:Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) allows real-time measurements of volatile organic compounds (VOCs) in air with a high sensitivity and a fast time response. The use of PTR-MS in atmospheric research has expanded rapidly in recent years, and much has been learned about the instrument response and specificity of the technique in the analysis of air from different regions of the atmosphere. This paper aims to review the progress that has been made. The theory of operation is described and allows the response of the instrument to be described for different operating conditions. More accurate determinations of the instrument response involve calibrations using standard mixtures, and some results are shown. Much has been learned about the specificity of PTR-MS from inter-comparison studies as well the coupling of PTR-MS with a gas chromatographic interface. The literature on this issue is reviewed and summarized for many VOCs of atmospheric interest. Some highlights of airborne measurements by PTR-MS are presented, including the results obtained in fresh and aged forest-fire and urban plumes. Finally, the recent work that is focused on improving the technique is discussed. © 2006 Wiley Periodicals, Inc. Mass Spec Rev 26:223–257, 2007
-
Measurements of volatile organic compounds in the earth's atmosphere using Proton-Transfer-Reaction Mass Spectrometry
Mass Spectrometry Reviews, 2007Co-Authors: Joost De Gouw, Carsten WarnekeAbstract:Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) allows real-time measurements of volatile organic compounds (VOCs) in air with a high sensitivity and a fast time response. The use of PTR-MS in atmospheric research has expanded rapidly in recent years, and much has been learned about the instrument response and specificity of the technique in the analysis of air from different regions of the atmosphere. This paper aims to review the progress that has been made. The theory of operation is described and allows the response of the instrument to be described for different operating conditions. More accurate determinations of the instrument response involve calibrations using standard mixtures, and some results are shown. Much has been learned about the specificity of PTR-MS from inter-comparison studies as well the coupling of PTR-MS with a gas chromatographic interface. The literature on this issue is reviewed and summarized for many VOCs of atmospheric interest. Some highlights of airborne measurements by PTR-MS are presented, including the results obtained in fresh and aged forest-fire and urban plumes. Finally, the recent work that is focused on improving the technique is discussed.
-
proton transfer reaction Mass Spectrometry as a new tool for real time analysis of root secreted volatile organic compounds in arabidopsis
Plant Physiology, 2004Co-Authors: Marco Steeghs, Joost De Gouw, Ray Fall, W C Kuster, P D Goldan, Harsh P Bais, Megan Northway, Jorge M VivancoAbstract:Plant roots release about 5% to 20% of all photosynthetically-fixed carbon, and as a result create a carbon-rich environment for numerous rhizosphere organisms, including plant pathogens and symbiotic microbes. Although some characterization of root exudates has been achieved, especially of secondary metabolites and proteins, much less is known about volatile organic compounds (VOCs) released by roots. In this communication, we describe a novel approach to exploring these rhizosphere VOCs and their induction by biotic stresses. The VOC formation of Arabidopsis roots was analyzed using Proton-Transfer-Reaction Mass Spectrometry (PTR-MS), a new technology that allows rapid and real time analysis of most biogenic VOCs without preconcentration or chromatography. Our studies revealed that the major VOCs released and identified by both PTR-MS and gas chromatography-Mass Spectrometry were either simple metabolites, ethanol, acetaldehyde, acetic acid, ethyl acetate, 2-butanone, 2,3,-butanedione, and acetone, or the monoterpene, 1,8-cineole. Some VOCs were found to be produced constitutively regardless of the treatment; other VOCs were induced specifically as a result of different compatible and noncompatible interactions between microbes and insects and Arabidopsis roots. Compatible interactions of Pseudomonas syringae DC3000 and Diuraphis noxia with Arabidopsis roots resulted in the rapid release of 1,8-cineole, a monoterpene that has not been previously reported in Arabidopsis. Mechanical injuries to Arabidopsis roots did not produce 1,8-cineole nor any C6 wound-VOCs; compatible interactions between Arabidopsis roots and Diuraphis noxia did not produce any wound compounds. This suggests that Arabidopsis roots respond to wounding differently from above-ground plant organs. Trials with incompatible interactions did not reveal a set of compounds that was significantly different compared to the noninfected roots. The PTR-MS method may open the way for functional root VOC analysis that will complement genomic investigations in Arabidopsis.
-
validation of proton transfer reaction Mass Spectrometry ptr ms measurements of gas phase organic compounds in the atmosphere during the new england air quality study neaqs in 2002
Journal of Geophysical Research, 2003Co-Authors: Joost De Gouw, W C Kuster, P D Goldan, C Warneke, James M Roberts, M Marchewka, Steven B Bertman, Alexander A P Pszenny, William C KeeneAbstract:[1] Organic compounds were measured by proton transfer reaction-Mass Spectrometry (PTR-MS) on board the National Oceanic and Atmospheric Administration's research ship Ronald H. Brown during the New England Air Quality Study (NEAQS) in July and August of 2002. PTR-MS has the potential to measure many important organic species with a fast time response, but its validity has not been proven sufficiently. The results obtained by PTR-MS during NEAQS were compared with those from (oxygenated) hydrocarbon measurements by gas chromatography/Mass Spectrometry (GC-MS), peroxyacyl nitrate measurements by gas chromatography/electron capture detection, and carboxylic acid measurements by mist chamber/ion chromatography. The PTR-MS and GC-MS data for methanol, acetonitrile, acetone, isoprene, benzene, and toluene agreed within the measurement uncertainties. The comparison for C 8 aromatics and acetaldehyde was less quantitative due to calibration inaccuracies. In addition, PTR-MS measured the sum of methyl vinyl ketone and methacrolein at 71 amu, the sum of C9 aromatics at 121 amu, and the sum of monoterpenes at 81 and 137 amu. The PTR-MS signal at 61 amu was found to correlate well with data for acetic acid. The signal at 73 amu correlated reasonably well with methyl ethyl ketone data, but the quantitative disagreement suggested interference from other species, possibly methyl glyoxal. The signal at 77 amu correlated well with data for peroxyacetyl nitrate, and the sensitivity inferred from the field data agreed within 30% with the results from laboratory calibrations. Finally, the signal at 105 amu was attributed to styrene and peroxy isobutyryl nitrate. These results prove that many important organic species can be measured accurately and with a fast response time by PTR-MS.
Chengyin Shen - One of the best experts on this subject based on the ideXlab platform.
-
detection of volatile organic compounds in a drop of urine by ultrasonic nebulization extraction proton transfer reaction Mass Spectrometry
Analytical Chemistry, 2018Co-Authors: Yan Lu, Hongmei Wang, Yating Zhang, Aiyue Li, Chaoqun Huang, Chengyin ShenAbstract:Detection of volatile organic compounds (VOCs) in human urine has potential application value in screening for disease and toxin exposure. However, the current technologies are too slow to detect the concentration of VOCs in fresh urine. In this study, we developed a novel ultrasonic nebulization extraction proton transfer reaction Mass Spectrometry (UNE-PTR-MS) technology. The urinary VOCs can be rapidly extracted to gaseous VOCs using the UNE system and then delivered using a carrier gas to the PTR-MS instrument for rapid detection. The carrier gas flow and sample size were optimized to 100 mL/min and 100 μL, respectively. The limits of detection (LODs) and response time of the UNE-PTR-MS were evaluated by detecting three VOCs that are common in human urine: methanol, acetaldehyde, and acetone. The LODs determined for methanol (4.47 μg/L), acetaldehyde (1.98 μg/L), and acetone (3.47 μg/L) are 2–3 orders of magnitude lower than the mean concentrations of that in healthy human urine. The response time of ...
-
rapid and sensitive on line monitoring 6 different kinds of volatile organic compounds in aqueous samples by spray inlet proton transfer reaction Mass Spectrometry si ptr ms
Chemosphere, 2017Co-Authors: Meng Kang, Chaoqun Huang, Hongmei Wang, Chengyin ShenAbstract:Abstract Rapid and sensitive monitoring of volatile organic compounds (VOCs) in aqueous samples is very important to human health and environmental protection. In this study, an on-line spray inlet proton transfer reaction Mass Spectrometry (SI-PTR-MS) method was developed for the rapid and sensitive monitoring of 6 different kinds of VOCs, namely acetonitrile, acetaldehyde, ethanol, acetone, aether, and methylbenzene, in aqueous samples. The response time, limit of detection (LOD), and repeatability of the SI-PTR-MS system were evaluated. The response of the SI-PTR-MS was quite rapid with response times of 31–88 s. The LODs for all these VOCs were below 10 μg/L. The LOD of methylbenzene was 0.9 μg/L, much lower than the maximum contaminant level (MCL) in drinking water. The repeatability of this method was evaluated with 5 replicate determinations. The relative standard deviations (RSDs) were in the range of 0.8–3.1%, indicating good repeatability. To evaluate the matrix effects, the SI-PTR-MS system was employed for on-line monitoring of these 6 VOCs in different aqueous matrices, including lake water, tap water, and waste water. The relative recoveries were in the range of 94.6–106.0% for the lake water, 96.3–105.6% for the tap water, and 95.6–102.9% for the waste water. The results indicate that the SI-PTR-MS method has important application values in the rapid and sensitive monitoring of VOCs in these aqueous samples. In addition, the effect of salt concentration on the extracting efficiency was evaluated. The results showed that the LOD of the SI-PTR-MS could be further decreased by changing the salt concentration.
-
spray inlet proton transfer reaction Mass Spectrometry si ptr ms for rapid and sensitive online monitoring of benzene in water
Analytical Chemistry, 2016Co-Authors: Xue Zou, Chengyin Shen, Meng Kang, Yannan ChuAbstract:Rapid and sensitive monitoring of benzene in water is very important to the health of people and for environmental protection. A novel and online detection method of spray inlet proton transfer reaction Mass Spectrometry (SI-PTR-MS) was introduced for rapid and sensitive monitoring of trace benzene in water. A spraying extraction system was coupled with the self-developed PTR-MS. The benzene was extracted from the water sample in the spraying extraction system and continuously detected with PTR-MS. The flow of carrier gas and salt concentration in water were optimized to be 50 sccm and 20% (w/v), respectively. The response time and the limit of detection of the SI-PTR-MS for detection of benzene in water were 55 s and 0.14 μg/L at 10 s integration time, respectively. The repeatability of the SI-PTR-MS was evaluated, and the relative standard deviation of five replicate determinations was 4.3%. The SI-PTR-MS system was employed for monitoring benzene in different water matrices, such as tap water, lake wat...
-
Control of solvent use in medical devices by proton transfer reaction Mass Spectrometry and ion molecule reaction Mass Spectrometry.
Journal of pharmaceutical and biomedical analysis, 2009Co-Authors: Yujie Wang, Haiyan Han, Chengyin Shen, Hongmei Wang, Yannan ChuAbstract:A homemade proton transfer reaction Mass spectrometer (PTR-MS) and a commercial ion molecule reaction Mass spectrometer (IMR-MS) have been applied to detect volatile organic compounds (VOCs) in the packaging bags of infusion sets made of polyvinylchloride (PVC) plastic. The most abundant characteristic ions in the PTR-MS and IMR-MS measurements are observed at m/z 99 and 98 respectively, which are the results of soft ionizations that a residual chemical undergoes the proton transfer reaction in PTR-MS and the charge transfer reaction in IMR-MS. On the basis of ionic intensity dependence on the reduced-field in the PTR-MS investigation, the residue can be unambiguously identified as cyclohexanone, a commonly used adhesive agent in PVC medical device manufacture. Quantitative measurement by PTR-MS shows that concentrations of cyclohexanone in the packages of two types of infusion sets are 11 and 20 ppm respectively. Due to fast response, absolute concentration detection, and high sensitivity, the PTR-MS and IMR-MS detection methods are proposed for the quality control of medical devices including the detection of illegal or excessive uses of chemical solvents like cyclohexanone.
Carsten Warneke - One of the best experts on this subject based on the ideXlab platform.
-
Evaluation of a New Vocus Reagent-Ion Source and Focusing Ion-Molecule Reactor for use in Proton-Transfer-Reaction Mass Spectrometry
2018Co-Authors: Jordan Krechmer, Carsten Warneke, Abigail R. Koss, Rupert Holzinger, Felipe D. Lopez-hilfiker, Manuel A. Hutterli, Carsten Stoermer, Benjamin L. Deming, Joel R. Kimmel, John T. JayneAbstract:We evaluate the performance of a new chemical ionization source called Vocus, consisting of a discharge reagent-ion source and focusing ion-molecule reactor (FIMR) for use in protontransfer-reaction time-of-flight Mass Spectrometry (PTR-TOF) measurements of volatile organic compounds (VOCs) in air. The reagent ion source uses a low-pressure discharge. The FIMR consists of a glass tube with a resistive coating, mounted inside a radio-frequency (RF) quadrupole. The axial electric field is used to enhance ion collision energies and limit cluster ion formation. The RF field focuses ions to the central axis of the reactor and improves the detection efficiency of product ions. Ion trajectory calculations demonstrate the Mass-dependent focusing of ions and enhancement of the ion collision energy by the RF field, in particular for the lighter ions. Product ion signals are increased by a factor of 10 when the RF field is applied (5,000-18,000 cps ppbv-1), improving measurement precision and detection limits while operating at very similar reaction conditions as traditional PTR instruments. Due to the high water mixing ratio in the FIMR, we observe no dependence of the sensitivity on ambient sample humidity. In this work, the Vocus is interfaced to a TOF Mass analyzer with a Mass resolving power up to 14,000, which allows clear separation of isobaric ions, observed at nearly every nominal Mass when measuring ambient air. Measurement response times are determined for a range of ketones with saturation vapor concentrations down to 5×104 μg m-3 and compare favorably with previously published results for a PTR-MS instrument.
-
Proton-Transfer-Reaction Mass Spectrometry: Applications in Atmospheric Sciences
Chemical reviews, 2017Co-Authors: Bin Yuan, Carsten Warneke, Abigail R. Koss, Matthew M. Coggon, Kanako Sekimoto, Joost De GouwAbstract:Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) has been widely used to study the emissions, distributions, and chemical evolution of volatile organic compounds (VOCs) in the atmosphere. The applications of PTR-MS have greatly promoted understanding of VOC sources and their roles in air-quality issues. In the past two decades, many new Mass spectrometric techniques have been applied in PTR-MS instruments, and the performance of PTR-MS has improved significantly. This Review summarizes these developments and recent applications of PTR-MS in the atmospheric sciences. We discuss the latest instrument development and characterization work on PTR-MS instruments, including the use of time-of-flight Mass analyzers and new types of ion guiding interfaces. Here we review what has been learned about the specificity of different product ion signals for important atmospheric VOCs. We present some of the recent highlights of VOC research using PTR-MS including new observations in urban air, bioMass-burning plumes,...
-
measurements of volatile organic compounds in the earth s atmosphere using proton transfer reaction Mass Spectrometry
Mass Spectrometry Reviews, 2007Co-Authors: Joost De Gouw, Carsten WarnekeAbstract:Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) allows real-time measurements of volatile organic compounds (VOCs) in air with a high sensitivity and a fast time response. The use of PTR-MS in atmospheric research has expanded rapidly in recent years, and much has been learned about the instrument response and specificity of the technique in the analysis of air from different regions of the atmosphere. This paper aims to review the progress that has been made. The theory of operation is described and allows the response of the instrument to be described for different operating conditions. More accurate determinations of the instrument response involve calibrations using standard mixtures, and some results are shown. Much has been learned about the specificity of PTR-MS from inter-comparison studies as well the coupling of PTR-MS with a gas chromatographic interface. The literature on this issue is reviewed and summarized for many VOCs of atmospheric interest. Some highlights of airborne measurements by PTR-MS are presented, including the results obtained in fresh and aged forest-fire and urban plumes. Finally, the recent work that is focused on improving the technique is discussed. © 2006 Wiley Periodicals, Inc. Mass Spec Rev 26:223–257, 2007
-
Measurements of volatile organic compounds in the earth's atmosphere using Proton-Transfer-Reaction Mass Spectrometry
Mass Spectrometry Reviews, 2007Co-Authors: Joost De Gouw, Carsten WarnekeAbstract:Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) allows real-time measurements of volatile organic compounds (VOCs) in air with a high sensitivity and a fast time response. The use of PTR-MS in atmospheric research has expanded rapidly in recent years, and much has been learned about the instrument response and specificity of the technique in the analysis of air from different regions of the atmosphere. This paper aims to review the progress that has been made. The theory of operation is described and allows the response of the instrument to be described for different operating conditions. More accurate determinations of the instrument response involve calibrations using standard mixtures, and some results are shown. Much has been learned about the specificity of PTR-MS from inter-comparison studies as well the coupling of PTR-MS with a gas chromatographic interface. The literature on this issue is reviewed and summarized for many VOCs of atmospheric interest. Some highlights of airborne measurements by PTR-MS are presented, including the results obtained in fresh and aged forest-fire and urban plumes. Finally, the recent work that is focused on improving the technique is discussed.
-
validation of atmospheric voc measurements by proton transfer reaction Mass Spectrometry using a gas chromatographic preseparation method
Environmental Science & Technology, 2003Co-Authors: Carsten Warneke, Joost De Gouw, W C Kuster, P D Goldan, Ray FallAbstract:Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) has emerged as a useful tool to study volatile organic compounds (VOCs) in the atmosphere. In PTR-MS, proton-transfer reactions with H3O+ ions are used to ionize and measure VOCs in air with a high sensitivity and fast time response. Only the Masses of the ionized VOCs and their fragments, if any, are determined, and these product ions are not unique indicators of VOC identities. Here, a combination of gas chromatography and PTR-MS (GC-PTR-MS) is used to validate the measurements by PTR-MS of a number of common atmospheric VOCs. We have analyzed 75 VOCs contained in standard mixtures by GC-PTR-MS, which allowed detected Masses to be unambiguously related to a specific compound. The calibration factors for PTR-MS and GC-PTR-MS were compared and showed that the loss of VOCs in the sample acquisition and GC system is small. GC-PTR-MS analyses of 56 air samples from an urban site were used to address the specificity of PTR-MS in complex air Masses. It is dem...
Armin Wisthaler - One of the best experts on this subject based on the ideXlab platform.
-
a novel method for producing nh4 reagent ions in the hollow cathode glow discharge ion source of ptr ms instruments
International Journal of Mass Spectrometry, 2020Co-Authors: Markus Muller, Philipp Sulzer, Armin Wisthaler, Eugen Hartungen, Felix Piel, Rene GutmannAbstract:Abstract Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) is seeing an increased use of NH4+ ions for the detection of amines and labile oxygenated organic compounds. NH4+ ions are usually generated from ammonia or ammonium-containing chemicals. We herein present a simple method for generating NH4+ reagent ions in the hollow cathode glow discharge ion source that nowadays most Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) instruments are equipped with. We show that NH4+ ions can be generated in high purity and yield by simply introducing a mixture of water vapor and nitrogen in the ion source. We also show that rapid switching (∼10 s loss of data) between the H3O+ and NH4+ operation modes is possible. Our new method can be easily implemented in most PTR-MS instruments that are currently in use, thus opening the possibility to easily operate the PTR-MS analyzer in the NH4+ chemical ionization mode.
-
bulk organic aerosol analysis by proton transfer reaction Mass Spectrometry an improved methodology for the determination of total organic Mass o c and h c elemental ratios and the average molecular formula
Analytical Chemistry, 2019Co-Authors: Joris Leglise, Markus Muller, Felix Piel, Tobias Otto, Armin WisthalerAbstract:We have recently shown in this journal (Muller et al. Anal. Chem. 2017, 89, 10889–10897) how a Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) analyzer measured particulate organic matter in ur...
-
direct sampling and analysis of atmospheric particulate organic matter by proton transfer reaction Mass Spectrometry
Analytical Chemistry, 2017Co-Authors: Markus Muller, Philipp Eichler, Wen Tan, Barbara Danna, Armin WisthalerAbstract:We report on a new method for analyzing atmospheric submicrometer particulate organic matter which combines direct particle sampling and volatilization with online chemical ionization Mass spectrometric analysis. Technically, the method relies on the combined use of a CHARON (“Chemical Analysis of Aerosol Online”) particle inlet and a Proton-Transfer-Reaction time-of-flight Mass spectrometer (PTR-ToF-MS). Laboratory studies on target analytes showed that the ionization conditions in the PTR-ToF-MS lead to extensive fragmentation of levoglucosan and cis-pinonic acid, while protonated oleic acid and 5α-cholestane molecules remain intact. Potential problems and biases in quantitative and qualitative analyses are discussed. Side-by-side atmospheric comparison measurements of total particulate organic Mass and levoglucosan with an aerosol Mass spectrometer (AMS) were in good agreement. Complex and clearly distinct organic Mass spectra were obtained from atmospheric measurements in three European cities (Lyon, ...
-
Direct Sampling and Analysis of Atmospheric Particulate Organic Matter by Proton-Transfer-Reaction Mass Spectrometry
2017Co-Authors: Markus Müller, Philipp Eichler, Barbara D’anna, Wen Tan, Armin WisthalerAbstract:We report on a new method for analyzing atmospheric submicrometer particulate organic matter which combines direct particle sampling and volatilization with online chemical ionization Mass spectrometric analysis. Technically, the method relies on the combined use of a CHARON (“Chemical Analysis of Aerosol Online”) particle inlet and a Proton-Transfer-Reaction time-of-flight Mass spectrometer (PTR-ToF-MS). Laboratory studies on target analytes showed that the ionization conditions in the PTR-ToF-MS lead to extensive fragmentation of levoglucosan and cis-pinonic acid, while protonated oleic acid and 5α-cholestane molecules remain intact. Potential problems and biases in quantitative and qualitative analyses are discussed. Side-by-side atmospheric comparison measurements of total particulate organic Mass and levoglucosan with an aerosol Mass spectrometer (AMS) were in good agreement. Complex and clearly distinct organic Mass spectra were obtained from atmospheric measurements in three European cities (Lyon, Valencia, Innsbruck). Data visualization in reduced-parameter frameworks (e.g., oxidation state of carbon vs carbon number) revealed that the CHARON-PTR-ToF-MS technique adds significant analytical capabilities for characterizing particulate organic carbon in the Earth’s atmosphere. Positive matrix factorization (PMF) was used for apportioning sources of atmospheric particles in late fall in Innsbruck. The m/z signatures of known source marker compounds (levoglucosan and resin acids, polycyclic aromatic hydrocarbons, nicotine) in the Mass spectra were used to assign PMF factors to bioMass burning, traffic, and smoking emission sources
-
on line monitoring of microbial volatile metabolites by proton transfer reaction Mass Spectrometry
Applied and Environmental Microbiology, 2008Co-Authors: Michael Bunge, A Hansel, Armin Wisthaler, Tomas Mikoviny, Nooshin Araghipour, J Dunkl, R Schnitzhofer, Franz Schinner, Rosa Margesin, T D MarkAbstract:A method for analysis of volatile organic compounds (VOCs) from microbial cultures was established using proton transfer reaction-Mass Spectrometry (PTR-MS). A newly developed sampling system was coupled to a PTR-MS instrument to allow on-line monitoring of VOCs in the dynamic headspaces of microbial cultures. The novel PTR-MS method was evaluated for four reference organisms: Escherichia coli, Shigella flexneri, Salmonella enterica, and Candida tropicalis. Headspace VOCs in sampling bottles containing actively growing cultures and uninoculated culture medium controls were sequentially analyzed by PTR-MS. Characteristic marker ions were found for certain microbial cultures: C. tropicalis could be identified by several unique markers compared with the other three organisms, and E. coli and S. enterica were distinguishable from each other and from S. flexneri by specific marker ions, demonstrating the potential of this method to differentiate between even closely related microorganisms. Although the temporal profiles of some VOCs were similar to the growth dynamics of the microbial cultures, most VOCs showed a different temporal profile, characterized by constant or decreasing VOC levels or by single or multiple peaks over 24 h of incubation. These findings strongly indicate that the temporal evolution of VOC emissions during growth must be considered if characterization or differentiation based on microbial VOC emissions is attempted. Our study may help to establish the analysis of VOCs by on-line PTR-MS as a routine method in microbiology and as a tool for monitoring environmental and biotechnological processes.
