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Fischer M.,University of Rostock | Fischer M.,Helmholtz Center Munich | Wohlfahrt S.,University of Rostock | Wohlfahrt S.,Helmholtz Center Munich | And 8 more authors.
Analytical Chemistry | Year: 2015

This work describes an ultrafast-cycling gas chromatography module (fast-GC module) for direct-sampling gas chromatography/mass spectrometry (GC-MS). The sample can be introduced into the fast-GC module using a common GC injector or any GC x GC modulator. The new fast-GC module offers the possibility to conduct a complete temperature cycle within 30 s. Its thermal mass is minimized by using a specially developed home-built fused silica capillary column stack and a halogen lamp for heat generation, both placed inside a gold-coated quartz glass cylinder. A high airflow blower enables rapid cooling. The new device is highly flexible concerning the used separation column, the applied temperature program, and the integration into existing systems. An application of the fast-GC module is shown in this work by thermal analysis coupled to gas chromatography-mass spectrometry (TA-GC-MS). The continuously evolving gases of the TA are modulated by a liquid CO2 modulator. Because of the rapid cycling of the fast-GC module, it is possible to obtain the best separation while maintaining the online character of the TA. Restrictions in separation and retention time shifting, known from isothermal and normal ramped fast-GC systems, are overcome. (Graph Presented). © 2015 American Chemical Society.


Wohlfahrt S.,Helmholtz Center Munich | Wohlfahrt S.,University of Rostock | Fischer M.,Helmholtz Center Munich | Fischer M.,University of Rostock | And 7 more authors.
Analytical Chemistry | Year: 2016

The design of the so-called "Peltier modulator" is presented. It is a new dual-stage consumable-free thermal modulator for thermal analysis-gas chromatography-mass spectrometry (TA-GC-MS). It requires only electrical power for operation as it facilitates thermo-electric coolers instead of cryogenics for trapping and resistive on-column heating for reinjection. Trapping and desorption temperatures as well as modulation cycles are freely adjustable. The stationary phase for the trapping region can be selected to suit the specific application, since common fused silica capillary is used. The Peltier modulator's performance is demonstrated with a broad range of different standard substances and with heavy crude oil as a complex real life sample. Successful modulation from n-pentane to pyrene (boiling points = 36/394°C) is presented. The produced peaks show the narrowest bandwidths ever reported for a consumable-free thermal modulator, i.e., 12.8 ± 1.2 ms for n-pentadecane. The Peltier modulator is rugged, cost-effective, requires low maintenance, and decreases security issues significantly, compared to commercial available solutions using liquid N2/CO2. © 2015 American Chemical Society.


Fischer M.,Helmholtz Center Munich | Fischer M.,University of Rostock | Wohlfahrt S.,Helmholtz Center Munich | Wohlfahrt S.,University of Rostock | And 7 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2014

The applicability of thermogravimetry (TG) coupled to single photon ionization time-of-flight mass spectrometry (TG-SPI-TOFMS) for evolved gas analysis (EGA) of coffee is demonstrated in this study. Coffee is a chemically well-known complex food product of large scientific and commercial interest. The roasting process of single green coffee beans (Arabica, Robusta) was simulated in the TG-SPI-TOFMS device, and the chemical composition of the evolved roasting gases was monitored on-line. Additionally, roasted and ground coffee powders of different types and brands as well as instant coffee were successfully investigated. For example, the diterpenes cafestol and kahweol can be detected among many other roasting products. These compounds can be of particular interest for quality control of coffee. It is shown that kahweol can be used as a tracer compound to discriminate arabica coffee species from robusta species. © Akadémiai Kiadó, Budapest, Hungary 2014.


Czech H.,University of Rostock | Schepler C.,University of Rostock | Klingbeil S.,University of Rostock | Klingbeil S.,Helmholtz Virtual Institute of Complex Molecular Systems in Environmental Health HICE | And 6 more authors.
Journal of Agricultural and Food Chemistry | Year: 2016

Coffee beans of two cultivars, Arabica (Mexico) and Robusta (Vietnam), were roasted in a small-scale drum roaster at different temperature profiles. Evolving volatile compounds out of the roasting off-gas were analyzed by photoionization mass spectrometry at four different wavelengths, either with single-photon ionization (SPI) or resonance-enhanced multiphoton ionization (REMPI). The different analyte selectivities at the four wavelengths and their relevance for the examination of the roasting process were discussed. Furthermore, intensities of observed m/z were grouped by non-negative matrix factorization (NMF) to reveal the temporal evolutions of four roasting phases ("evaporation", "early roast", "late roast", and "overroast") from NMF scores and the corresponding molecular composition from the NMF factor loadings, giving chemically sound results concerning the roasting phases. Finally, linear classifiers were constructed from real mass spectra at maximum NMF scores by linear discriminant analysis to obtain quantities which are simple to measure for real-time analysis of the roasting process. © 2016 American Chemical Society.


Groger T.,Helmholtz Center Munich | Groger T.,University of Rostock | Gruber B.,Helmholtz Center Munich | Gruber B.,University of Rostock | And 7 more authors.
Analytical Chemistry | Year: 2016

Fast and selective detectors are very interesting for comprehensive two-dimensional gas chromatography (GC × GC). This is particularly true if the detector system can provide additional spectroscopic information on the compound structure and/or functionality. Other than mass spectrometry (MS), only optical spectroscopic detectors are able to provide selective spectral information. However, until present the application of optical spectroscopy technologies as universal detectors for GC × GC has been restricted mainly due to physical limitations such as insufficient acquisition speed or high detection limits. A recently developed simultaneous-detection spectrometer working in the vacuum ultraviolet (VUV) region of 125-240 nm overcomes these limitations and meets all the criteria of a universal detector for GC × GC. Peak shape and chromatographic resolution is preserved and unique spectral information, complementary to mass spectrometry data, is gained. The power of this detector is quickly recognized as it has the ability to discriminate between isomeric compounds or difficult to separate structurally related isobaric species; thus, it provides additional selectivity. A further promising feature of this detector is the data analysis concept of spectral filtering, which is accomplished by targeting special electronic transitions that allows for a fast screening of GC × GC chromatograms for designated compound classes. (Figure Presented). © 2016 American Chemical Society.


Fischer M.,Helmholtz Center Munich | Wohlfahrt S.,Helmholtz Center Munich | Saraji-Bozorgzad M.,Photonion GmbH | Matuschek G.,Helmholtz Center Munich | And 5 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2013

A simultaneous thermogravimetry/differential scanning calorimetry device (STA) was coupled to single photon ionization time of flight mass spectrometry (SPI-TOFMS) for evolved gas analysis (EGA). Thermal resolution with thermogravimetric signals (TG/DTG) is delivered by STA. On-line coupled EGA with SPI-TOFMS retains the thermal information from the STA and substantiates these with correlating mass spectra. The application of vacuum ultraviolet (VUV)-photons (8-12 eV) for soft ionization, allows almost fragment-free ionization. Thus, it becomes possible to interpret mass spectra of complex matrices, like natural products evolving simultaneously several molecules, without an additional separation step. The STA-SPI-TOFMS on-line coupling offers the possibility to track subset mass traces during one STA run. Focusing on material-depended mass traces, differentiation of organic matrices is obvious. In this work two types of research cigarettes, 3R4F and CM6 were used. While the 3R4F cigarette is composed of a blend of different tobacco sorts and different curing methods, the CM6 research cigarette consists of pure flue cured tobacco. The advantages of coupling on-line chemical analysis methods to thermal analysis (TA) are in the context of the achieved thermo-molecular signatures. © 2013 Akadémiai Kiadó, Budapest, Hungary.


Wohlfahrt S.,Helmholtz Center Munich | Fischer M.,Helmholtz Center Munich | Saraji-Bozorgzad M.,Photonion GmbH | Matuschek G.,Helmholtz Center Munich | And 4 more authors.
Analytical and Bioanalytical Chemistry | Year: 2013

Comprehensive multi-dimensional hyphenation of a thermogravimetry device (i.e. a thermobalance) to gas chromatography and single photon ionization-time-of-flight mass spectrometry (TG-GC×SPI-MS) has been used to investigate two crude oil samples of different geographical origin. The source of the applied vacuum ultraviolet radiation is an electron beam pumped rare gas excimer lamp (EBEL). The soft photoionization favors the formation of molecular ions. Introduction of a fast, rapidly modulated gas chromatographic separation step in comparison with solely TG-SPI-MS enables strongly enhanced detection especially with such highly complex organic matrices as crude oil. In contrast with former TG-SPI-MS measurements, separation and identification of overlying substances is possible because of different GC retention times. The specific contribution of isobaric compounds to one mass signal is determined for alkanes, naphthalenes, alkylated benzenes, and other compounds. © 2013 Springer-Verlag Berlin Heidelberg.


PubMed | Photonion GmbH, Helmholtz Center Munich, University of Rostock, Airsense Analytics GmbH and Netzsch Geraetebau GmbH
Type: Journal Article | Journal: Analytical chemistry | Year: 2015

This work describes an ultrafast-cycling gas chromatography module (fast-GC module) for direct-sampling gas chromatography/mass spectrometry (GC-MS). The sample can be introduced into the fast-GC module using a common GC injector or any GC GC modulator. The new fast-GC module offers the possibility to conduct a complete temperature cycle within 30 s. Its thermal mass is minimized by using a specially developed home-built fused silica capillary column stack and a halogen lamp for heat generation, both placed inside a gold-coated quartz glass cylinder. A high airflow blower enables rapid cooling. The new device is highly flexible concerning the used separation column, the applied temperature program, and the integration into existing systems. An application of the fast-GC module is shown in this work by thermal analysis coupled to gas chromatography-mass spectrometry (TA-GC-MS). The continuously evolving gases of the TA are modulated by a liquid CO2 modulator. Because of the rapid cycling of the fast-GC module, it is possible to obtain the best separation while maintaining the online character of the TA. Restrictions in separation and retention time shifting, known from isothermal and normal ramped fast-GC systems, are overcome.


PubMed | Photonion GmbH, Helmholtz Center Munich, University of Rostock and Netzsch Geraetebau GmbH
Type: Journal Article | Journal: Analytical chemistry | Year: 2016

The design of the so-called Peltier modulator is presented. It is a new dual-stage consumable-free thermal modulator for thermal analysis-gas chromatography-mass spectrometry (TA-GC-MS). It requires only electrical power for operation as it facilitates thermo-electric coolers instead of cryogenics for trapping and resistive on-column heating for reinjection. Trapping and desorption temperatures as well as modulation cycles are freely adjustable. The stationary phase for the trapping region can be selected to suit the specific application, since common fused silica capillary is used. The Peltier modulators performance is demonstrated with a broad range of different standard substances and with heavy crude oil as a complex real life sample. Successful modulation from n-pentane to pyrene (boiling points = 36/394 C) is presented. The produced peaks show the narrowest bandwidths ever reported for a consumable-free thermal modulator, i.e., 12.8 1.2 ms for n-pentadecane. The Peltier modulator is rugged, cost-effective, requires low maintenance, and decreases security issues significantly, compared to commercial available solutions using liquid N2/CO2.


PubMed | Photonion GmbH, Helmholtz Center Munich, University of Rostock and Vuv Analytics
Type: Journal Article | Journal: Analytical chemistry | Year: 2016

Fast and selective detectors are very interesting for comprehensive two-dimensional gas chromatography (GC GC). This is particularly true if the detector system can provide additional spectroscopic information on the compound structure and/or functionality. Other than mass spectrometry (MS), only optical spectroscopic detectors are able to provide selective spectral information. However, until present the application of optical spectroscopy technologies as universal detectors for GC GC has been restricted mainly due to physical limitations such as insufficient acquisition speed or high detection limits. A recently developed simultaneous-detection spectrometer working in the vacuum ultraviolet (VUV) region of 125-240 nm overcomes these limitations and meets all the criteria of a universal detector for GC GC. Peak shape and chromatographic resolution is preserved and unique spectral information, complementary to mass spectrometry data, is gained. The power of this detector is quickly recognized as it has the ability to discriminate between isomeric compounds or difficult to separate structurally related isobaric species; thus, it provides additional selectivity. A further promising feature of this detector is the data analysis concept of spectral filtering, which is accomplished by targeting special electronic transitions that allows for a fast screening of GC GC chromatograms for designated compound classes.

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