New advances in separation science for metabolomics: resolving chemical diversity in a post-genomic era

Metabolomics aims to identify the changes in endogenous metabolites of biological systems in response to intrinsic and extrinsic factors. This is accomplished through untargeted, semi-targeted and targeted based approaches. Untargeted and semi-targeted methods are typically applied in hypothesis-generating investigations (aimed at measuring as many metabolites as possible), while targeted approaches analyze a relatively smaller subset of biochemically important and relevant metabolites. Regardless of approach, it is well recognized amongst the metabolomics community that gas chromatography-mass spectrometry (GC–MS) is one of the most efficient, reproducible and well used analytical platforms for metabolomics research. This is due to the robust, reproducible and selective nature of the technique, as well as the large number of well-established libraries of both commercial and ‘in house’ metabolite databases available. This review provides an overview of developments in GC–MS based metabolomics applications, with a focus on sample preparation and preservation techniques. A number of chemical derivatization (in-time, in-liner, offline and microwave assisted) techniques are also discussed. Electron impact ionization and a summary of alternate mass analyzers are highlighted, along with a number of recently reported new GC columns suited for metabolomics. Lastly, multidimensional GC–MS and its application in environmental and biomedical research is presented, along with the importance of bioinformatics. The purpose of this review is to both highlight and provide an update on GC–MS analytical techniques that are common in metabolomics studies. Specific emphasis is given to the key steps within the GC–MS workflow that those new to this field need to be aware of and the common pitfalls that should be looked out for when starting in this area.

Review of recent developments in GC-MS approaches to metabolomics-based research.

We review the literature on comprehensive two-dimensional gas chromatography (GC × GC), emphasizing developments in the period 2003–2005. The review opens with a general introduction, the principles of the technique and the set-up of GC × GC systems. It also discusses theoretical aspects, trends in instrumentation, column combinations, and detection techniques – notably mass spectrometric detection. We devote attention to a wide variety of applications and to analytical performance.

Recent developments in comprehensive two-dimensional gas chromatography (GC × GC): I. Introduction and instrumental set-up

Lignocellulosic biomass is the most abundant organic carbon source and has received a great deal of interest as renewable and sustainable feedstock for the production of potential biofuels and value-added chemicals with a wide range of designed catalytic systems. However, those natural polymeric materials are composed of short-chain monomers (typically C6 and C5 sugars) and complex lignin molecules containing plenty of oxygen, resulting in products during the downstream processing having low-grade fuel properties or limited applications in organic syntheses. Accordingly, approaches to increase the carbon-chain length or carbon atom number have been developed as crucial catalytic routes for upgrading biomass into energy-intensive fuels and chemicals. The primary focus of this review is to systematically describe the recent examples on the selective synthesis of long-chain oxygenates via different C-C coupling catalytic processes, such as Aldol condensation, hydroalkylation/alkylation, oligomerization, keto...

Carbon-Increasing Catalytic Strategies for Upgrading Biomass into Energy-Intensive Fuels and Chemicals

■ CONTENTS Main Types of MDGC 558 Heart-Cutting Two-Dimensional Gas Chromatography 558 Comprehensive Two-Dimensional Gas Chromatography 558 Fundamental Advances 558 New Modes of Implementation 558 Hybrid MDGC 558 Smart MDGC Interfaces 559 High-Speed GC × GC 559 High Temperature GC × GC 559 Coupling SFC to GC × GC 559 GC × GC Hardware Development and Method Optimization 559 New GC × GC Modulators 559 Comparison of Thermal and Flow Modulation 560 Studying the Precision of Low Duty Cycle Modulation GC × GC 560 Influence of Experimental Conditions on GC × GC Separations 560 Improved Mass Spectrometric Detection for GC × GC 561 Ionic Liquid Stationary Phases and MDGC 562 Unique Combinations of GC × GC Stationary Phases 562 GC × GC Retention Models 562 Predicting GC × GC Retention Times 562 Retention Indices and GC × GC 562 GC × GC Data Analysis 563 Improved 2-D Peak Integration 563 Multivariate Analysis of GC × GC Chromatograms 563 Applications of MDGC 564 Fuels and Industrial Chemicals 564 Examining Low Volatility/High Complexity Mixtures 564 Petroleum Biomarker Determination 565 Composition of Coal-Derived Materials 565 Alternative Fuel Characterization 566 GC × GC Separations of Miscellaneous Fuels and Industrial Mixtures 567 Environmental Analysis 567 Atmospheric Analysis 567 Water Analysis 567 Soil and Sediments 568 Biological Matrices 568 Commercial Products 569 Foods, Flavors, and Fragrances 569 Essential Oils 569 Personal Care Products 570 Agricultural Products 570 Wine Analysis 571 Biological Studies 572 Drug Analysis 572 VOC Emissions Resulting From Decaying Flesh 572 VOC Emissions From Specific Organisms 572 Analysis of Cells and Biofluids 573 Metabolomics 573 Summary of Instrument Configurations used for Applications 574 Conclusions 575 Author Information 575 Corresponding Author 575 Notes 575 Biographies 575 References 575

Multidimensional gas chromatography: fundamental advances and new applications

This work documents the development of the title system wherein the first dimension is a separation of polyolefins, according to composition, via an adsorption mechanism on a HYPERCARB stationary p...

Development of Comprehensive Two-Dimensional High Temperature Liquid Chromatography × Gel Permeation Chromatography for Characterization of Polyolefins.

Low-temperature oligomerization of 1-butene with H-ferrierite

A reversed-flow differential flow modulator for comprehensive two-dimensional gas chromatography

One-pot microwave derivatization of target compounds relevant to metabolomics with comprehensive two-dimensional gas chromatography

A method and apparatus for chromatography of a polyolefin polymer by flowing a solution of the polyolefin polymer through liquid flowing through a graphitic carbon liquid chromatography stationary phase. The method can be used to determine the monomer to comonomer ratio of a polyolefin copolymer such as a copolymer of ethylene and 1-octene or a copolymer of propylene and ethylene.

William L. Winniford

Papers

Development of Comprehensive Two-Dimensional High Temperature Liquid Chromatography × Gel Permeation Chromatography for Characterization of Polyolefins.

Low-temperature oligomerization of 1-butene with H-ferrierite

A reversed-flow differential flow modulator for comprehensive two-dimensional gas chromatography

One-pot microwave derivatization of target compounds relevant to metabolomics with comprehensive two-dimensional gas chromatography

Chromatography of polyolefin polymers