Application of parallel computing to speed up chemometrics for GC×GC-TOFMS based metabolic fingerprinting.

Parallel computing was tested regarding its ability to speed up chemometric operations for data analysis. A set of metabolic samples from a second hand smoke (SHS) experiment was analyzed with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS). Data was further preprocessed and analyzed. The preprocessing step comprises background correction, smoothing and alignment of the chromatographic signal. Data analysis was performed by applying t-test and partial least squares projection to latent structures discriminant analysis (PLS-DA). The optimization of the algorithm for parallel computing led to a substantial increase in performance. Metabolic fingerprinting showed a discrimination of the samples and indicates a metabolic effect of SHS

Automated compound classification for ambient aerosol sample separations using comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry.

Comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry (GC × GC–TOF-MS) is useful in analyzing complex samples, such as the semi-volatile organic compounds (SVOC) in daily aerosol samples collected in Augsburg, Germany. For efficient routine analysis, a partial classification system based on mass spectra has been proposed to group compounds into substance classes. Classifiers based on fragmentation patterns, retention time, and spectral transformations are incorporated into software scripts for automated classification. Fragmentation pattern rules are also applied to an aerosol sample analyzed using direct thermal desorption (DTD)–GC × GC–TOF-MS and a non-traditional column combination

Advanced scripting for the automated profiling of two-dimensional gas chromatography-time-of-flight mass spectrometry data from combustion aerosol.

Multidimensional gas chromatography is an appropriate tool for the non-targeted and comprehensive characterisation of complex samples generated from combustion processes. Particulate matter (PM) emission is composed of a large number of compounds, including condensed semi-volatile organic compounds (SVOCs). However, the complex amount of information gained from such comprehensive techniques is associated with difficult and time-consuming data analysis. Because of this obstacle, two-dimensional gas chromatography still receives relatively little use in aerosol science [1-4]. To remedy this problem, advanced scripting algorithms based on knowledge-based rules (KBRs) were developed in-house and applied to GCxGC-TOFMS data. Previously reported KBRs and newer findings were considered for the development of these algorithms. The novelty of the presented advanced scripting tools is a notably selective search criterion for data screening, which is primarily based on fragmentation patterns and the presence of specific fragments. Combined with "classical" approaches based on retention times, a fast, accurate and automated data evaluation method was developed, which was evaluated qualitatively and quantitatively for type 1 and type 2 errors. The method's applicability was further tested for PM filter samples obtained from ship fuel combustion. Major substance classes, including polycyclic aromatic hydrocarbons (PAH), alkanes, benzenes, esters and ethers, can be targeted. This approach allows the classification of approximately 75% of the peaks of interest within real PM samples. Various conditions of combustion, such as fuel composition and engine load, could be clearly characterised and differentiated

Gas chromatography in combination with fast high-resolution time-of-flight mass spectrometry: Technical overview and perspectives for data visualization.

Time-of-flight mass spectrometry combines fast acquisition speed with the ability to collect full spectral information and over the last years also high mass resolution instrumentation became available for customers. These features make TOFMS very interesting for the hyphenation with fast or comprehensive two-dimensional gas chromatography. This publication reviews the technical progress of TOF-techniques with the focus on their compatibility with fast and ultra-fast chromatographic separations. A special focus is put on ionization techniques and data visualization approaches, covering related review article as well as selected primary literature and studies

Photo-ionisation mass spectrometry as detection method for gas chromatography. Optical selectivity and multidimensional comprehensive separations.

Mass spectrometry (MS) with soft ionisation techniques (i.e. ionisation without fragmentation of the analyte molecules) for gaseous samples exhibits interesting analytical properties for direct analysis applications (i.e. direct inlet mass spectrometric on-line monitoring) as well as mass spectrometric detection method for gas chromatography (GC-MS). Commonly either chemical ionisation (CI) or field ionisation (FI) is applied as soft ionisation technology for GC-MS. An interesting alternative to the CI and FI technologies methods are photo-ionisation (PI) methods. PI overcomes some of the limitations of CI and FI and furthermore add some unique analytical properties. The resonance enhanced multi-photon ionisation (REMPI) method uses intense UV-laser pulses (wavelength range approximately 350-193 nm) for highly selective, sensitive and soft ionisation of predominately aromatic compounds. The single photon ionisation (SPI) method utilises VUV light (from lamps or laser sources, wavelengths range approximately 150-110 nm) can be used for a universal soft ionisation of organic molecules. In this article the historical development as well as the current status and concepts of gas chromatography hyphenated to photo-ionisation mass spectrometry are reviewed

Online comprehensive two-dimensional characterization of puff-by-puff resolved cigarette smoke by hyphenation of fast gas chromatography to single-photon ionization time-of-flight mass spectrometry: Quantification of hazardous volatile organic compounds.

This work presents the direct coupling of a custom-made smoking machine (SM) to fast gas chromatography combined with single-photon ionization mass spectrometry (GC × SPI-MS) utilizing a six-port, two-position valve for online puff-resolved comprehensive two-dimensional investigation of cigarette smoke. The innovative electron-beam pumped rare gas excimer light source (EBEL) filled with argon provided vacuum ultraviolet (VUV) photons of 9.8 ± 0.4 eV (126 ± 9 nm) for SPI. Puff-by-puff quantification of 14 hazardous volatile organic smoke constituents from the 2R4F Kentucky research cigarette was enabled for two smoking regimes, i.e., ISO and Canadian Intense, after determination of photoionization cross sections. The investigated analytes comprised NO, acetaldehyde, butadiene, acrolein, propanal, acetone, isoprene, furan, crotonaldehyde, isobutanal, butanal, 2-butanone, benzene, and toluene. The determined amounts of these compounds in cigarette smoke agreed excellently with the literature values. Furthermore, the two well-known patterns of puff-by-puff behaviors for these different smoke constituents were obtained for both whole smoke and gas-phase measurements

Vacuum ultra violet spectroscopy as a complementary detection system to mass spectrometry for one- and comprehensive two-dimensional gas chromatography.

Vacuum ultraviolet (VUV) radiation and light sources are a common part of detection systems for gas and liquid chromatography. In most cases their ability to ionize molecules (photoionization) is used to generate charged ions which could be either quantitatively detected due to the induces current between two electrodes (e.g. Photoionization Detector, PID) or they could be further separated by their mass in combination with a mass spectrometer (e.g. single photon ionization mass spectrometry, SPIMS or atmospheric pressure photoionization, APPI). Even though in both cases only a small fraction of the adsorbed light is used for ionization or dissociation, the sensitivity of the overall detection system is sufficient for many applications. Compared with this, direct spectroscopic applications in chemical analytical laboratories have only rarely been reported in literature due to the peculiarity of VUV radiation and normally accompanied by an extensive instrumental setup. The recently introduced VGA-100 detector overcomes most of the instrumental obstacles and enables the direct coupling of a VUV spectrometer with gas chromatography. Probing of electronic and vibrionic states in the VUV range results in very distinct spectra as well as low detection limits compared to common UV absorption spectroscopy. The sensitivity and selectivity of the detector allow the application in fields where mass spectrometry is normally used. The ability for deconvolution of coeluting compounds based on spectral features as well as for quantification makes VUV spectroscopy a complementary detection system next to mass spectrometry

Vacuum ultraviolet absorption spectroscopy in combination with comprehensive two-dimensional gas chromatography for the monitoring of volatile organic compounds in breath gas: A feasibility study.

Vacuum ultraviolet (VUV) absorption spectroscopy was recently introduced as a new detection system for one, as well as comprehensive two-dimensional gas chromatography (GC×GC) and successfully applied to the analysis of various analytes in several matrices. In this study, its suitability for the analysis of breath metabolites was investigated and the impact of a finite volume of the absorption cell and makeup gas pressure was evaluated for volatile analytes in terms of sensitivity and chromatographic resolution. A commercial available VUV absorption spectrometer was coupled to GC×GC and applied to the analysis of highly polar volatile organic compounds (VOCs). Breath gas samples were acquired by needle trap micro extraction (NTME) during a glucose challenge and analysed by the applied technique. Regarding qualitative and quantitative information, the VGA-100 is compatible with common GC×GC detection systems like FID and even TOFMS. Average peak widths of 300ms and LODs in the lower ng range were achieved using GC×GC-VUV. Especially small oxygenated breath metabolites show intense and characteristic absorption patterns in the VUV region. Challenge responsive VOCs could be identified and monitored during a glucose challenge. The new VUV detection technology might especially be of benefit for applications in clinical research

Multidimensionale Analytik komplexer Systeme mit GC und MS.

Weiche Photoionisations-Massenspektrometrie gekoppelt mit zweidimensionaler Gaschromatographie trennt komplexe Gemische kleiner Moleküle, beispielsweise eine Dieselprobe oder biologische Metaboliten