Rapid Screening of Complex Matrices: Utilizing Kendrick Mass Defect To Enhance Knowledge-Based Group Type Evaluation of Multidimensional Gas Chromatography-High-Resolution Time-of-Flight Mass Spectrometry Data.

Organic compound characterization of highly complex matrices involves scientific challenges, such as the diversity of "true" unknowns, the concentration ranges of various compound classes, and limited available amounts of sample. Therefore, discovery-based multidimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry (GC×GC-HRToFMS) is increasingly applied. Nevertheless, most studies focus on target analysis and tend to disregard important details of the sample composition. The increased peak or separation capacity of GC×GC-ToFMS allows for in-depth chemical analysis of the molecular composition. However, high amounts of data, containing several thousands of compounds per experiment, are generally acquired during such analyses. Coupling GC×GC to high-resolution mass spectrometry further increases the amount of data and therefore requires advanced data reduction and mining techniques. Commonly, the main approach for the evaluation of GC×GC-HRToFMS data sets either focuses on the chromatographic separation (e.g., group type analysis), or utilizes exact mass data applying Kendrick mass defect analysis or van Krevelen plots. The presented approach integrates the accurate mass data and the chromatographic information by combining Kendrick mass defect information and knowledge-based rules. This combination allows for fast, visual data screening as well as quantitative estimation of the sample's composition. Moreover, the resulting sample classification significantly reduces the number of variables, allowing distinct chemometric analysis in nontargeted studies, such as detailed hydrocarbon analyses and environmental and forensic investigations.

A Vacuum Ultraviolet Absorption Array Spectrometer as a Selective Detector for Comprehensive Two-Dimensional Gas Chromatography: Concept and First Results.

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.

Facilitators and barriers to implementation of suicide prevention interventions: Scoping review.

We know that suicide is preventable, yet hundreds of thousands of people still die due to suicide every year. Many interventions were proven to be effective, and dozens of others showed promising results. However, translating these interventions into new settings brings several challenges. One of the crucial obstacles to success is not anticipating possible barriers to implementation nor enhancing possible benefits of factors facilitating the implementation. While we witnessed great support for suicide prevention activities globally in the past years, implementation barriers and facilitating factors are yet to be comprehensively mapped to help implementation activities worldwide. This scoping review maps current knowledge on facilitators and barriers to the implementation of suicide prevention interventions while using the Consolidated Framework for Implementation Research (CFIR) for classification. We included 64 studies. Barriers and facilitators were most commonly identified in the outer setting CFIR domain, namely in the sub-domain of patient needs and resources, which refers to the way in which these needs and resources are reflected by the reviewed interventions. The second most saturated CFIR domain for facilitators was intervention characteristics, where relative advantage, adaptability and cost of intervention sub-domains were equally represented. These sub-domains refer mostly to how the intervention is perceived by key stakeholders, to what extent it can be tailored to the implementation context and how much it costs. While intervention characteristics domain was the second most common also for barriers, the complexity sub-domain referring to high perceived difficulty of implementation was the most frequently represented. With reference to the results, we recommend adapting interventions to the needs of the target groups. Furthermore, carefully selecting the intervention to suit the target context concerning their adaptability, costs and complexity is vital for a successful implementation. Further implications for practice and research are discussed.

Modified QuEChERS extraction for the analysis of young-of-year smallmouth bass using GC × GC-TOFMS.

Signs of disease, such as external lesions, have been prevalent in smallmouth bass throughout the Susquehanna River Basin, USA. Previous targeted chemical studies in this system have identified known persistent organic pollutants, but a common explanatory link across multiple affected sites remains undetermined. A fast and robust extraction method that can be applied to young-of-year fish is needed to effectively screen for target and non-target compounds that may be impacting organism health. The quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction methodology was optimized to perform both targeted and non-targeted chemical analyses from a single extraction of whole young-of-year fish. Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOFMS) was used for extract analysis. Sample extraction was performed using the solvent ethyl acetate, followed by a two-step cleanup in which samples were frozen for lipid removal and subjected to dispersive solid phase extraction using Florisil. A sample of 21 young-of-year smallmouth bass collected from areas with disease and exhibiting different types of external lesions were evaluated for 233 target compounds. A total of 34 organic contaminants, including polychlorinated biphenyls, brominated diphenyl ethers, organochlorinated pesticides, and personal care products, were detected. Data from this sample set was then analyzed for non-targets. Using the Fisher ratio method and multivariate analysis, an additional 10 significant features were identified specific to either fish with visible lesions or with no visible disease characteristics.

Evaluation and application of gas chromatography - vacuum ultraviolet spectroscopy for drug- and explosive precursors and examination of non-negative matrix factorization for deconvolution.

Since the introduction of a benchtop vacuum ultraviolet (VUV) absorption spectroscope with an increased wavelength range towards to the high energetic ultraviolet radiation, gas chromatography coupled to VUV has been proven a powerful tool in several fields of application such as petroleomics, permanent gas analytic, pesticide analytic and many more. In this study, the potential of GC-VUV for investigations was examined, focusing on drug- and explosive precursors as well as chemical warfare simulants. The ability of VUV absorption spectra to differentiate isomers is presented, among others for nitroaromatics. In addition, the limit of detection for target compounds was determined to 0.7 ng absolute on column. Furthermore, non-negative matrix factorization (NMF) was successfully implemented as alternative deconvolution approach and evaluated for the deconvolution of unknown substances. In comparison, the spectral library-based deconvolution was applied to a standard mixture and a simulated case study. The results reveal that the NMF is a useful additional tool for deconvolution because, unlike library-based deconvolution, it allows to investigate unknown substances as well.

A minimal-invasive method for systemic bio-monitoring of the environmental pollutant phenanthrene in humans: Thermal extraction and gas chromatography - mass spectrometry from 1 mL capillary blood.

Phenanthrene is present in numerous environmental media and serves as a model substrate for the biomonitoring of polycyclic aromatic hydrocarbon (PAH). PAH exposure studies are commonly focused on urinary metabolites, concentrations of which are dependent on absorption, biotransformation and excretion. Monitoring of unmetabolized PAHs in blood would allow more reliable exposure assessment, but requires invasive sampling and extensive sample preparation. We describe the analysis of phenanthrene in 1µL capillary blood using thermal extraction (TE) combined with gas chromatography - mass spectrometry (GC-MS). Less invasive sampling of 1µL capillary blood does not require the assistance of medical staff. Compared to previous studies, analysis time was improved significantly by TE due to minimization of sample preparation steps. The evaluate method was applied successfully to the monitoring of phenanthrene blood levels. This is the first report presenting the pharmacokinetics of unmetabolized PAHs in human.

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.

Breath gas monitoring during a glucose challenge by a combined PTR-QMS/GC×GC-TOFMS approach for the verification of potential volatile biomarkers.

Breath gas profiles, which reflect metabolic disorders like diabetes, are the subject of scientific focus. Nevertheless, profiling is still a challenging task that requires complex and standardized methods. This study was carried out to verify breath gas patterns that were obtained in previous proton-transfer reaction-quadrupole mass spectrometry (PTR-QMS) studies and that can be linked to glucose metabolism. An experimental setup using simultaneous PTR-QMS and complementary highly time-resolved needle trap micro extraction (NTME) combined with comprehensive 2D gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) was established for the analysis of highly polar volatile organic compounds (VOCs). The method was applied to the breath gas analysis of three volunteers during a glucose challenge, whereby subjects ingested a glucose solution orally. Challenge responsive PTR-QMS target VOCs could be linked to small n-carbonic (C2-C4) alcohols and short chain fatty acids (SCFA). Specific isomers could be identified by simultaneously applied NTME-GC×GC-TOFMS and further verified by their characteristic time profiles and concentrations. The identified VOCs potentially originate from bacteria that are found in the oral cavity and gastrointestinal tract. In this study breath gas monitoring enabled the identification of potential VOC metabolites that can be linked to glucose metabolism.