The book will review the basic concepts and highlight the most relevant advances and developments that have taken place in the field of comprehensive two dimensional gas chromatography (GC x GC) since its introduction in 1991. The several instrumental and technical approaches assayed and developed during these fifteen years and that have contributed to the development of this powerful separation technique and to its increasing application in many application areas will be explained and comprehensively illustrated through a number of chapters devoted these specific topics. More specialized aspects of the technique, including theoretical aspects, modelization of the chromatographic process, software developments, and alternative couplings will also be covered. Finally, special attention will be paid to data treatment, for both qualitative and quantitative analysis. This book will be a practical resource that will explain from basic to specialized concepts of GC x GC and will show the current state-of-the-art and discuss future trends of this technique.The book will contain 12 chapters written by different experts in each particular topic or application field and will be organized in two sections. Part I will cover the principles of the technique, its basic concepts and instrumentation, theoretical aspects, and some specialized topics devoted to data analysis, last developments and future trends. After an introductory chapter, in which the concept of Â¡Â§multidimensionalityÂ¡Â¨ in gas chromatography will be discussed and the key issues, problems and challenges in GC x GC presented, the basic instrumentation for GC x GC will be described. The description of the several constituents of the basic GC x GC instrument will provide the reader the required understanding about the nature of the separation process in GC x GC and the relevance and potential influence of the different parts of the instrument in the final separation and detection of the analytes. The basic requirements of the GC columns, the different possible analytical approaches and the basic criteria for column selection will be explained. This chapter will also review the several models and types of modulators developed to interface the two GC columns involved in the separation process, highlighting their relative merits. The basic requirement for the detectors to be used in combination with GC ?e GC will be explained and the main advantages, limitations and respective application fields of the most frequently used ones revised. The basic theory behind the GC x GC process is not evident and because of the novelty of the technique, it has not been until recently that the practitioners agreed about the nomenclature to be used to define the chromatographic concepts involved in the process. The more relevant aspects in this field will be covered in a specific chapter about theoretical aspects. The several attempts to model the GC x GC process on the basis of present knowledge will be summarized and future demands in this particular field stated.The counterpoint to the high separation power of GC x GC is the complexity of the resulting chromatograms and the associated data file, peak list and quantitative data. The treatment of the high density GC x GC data set requires sophisticated algorithms to generate the characteristic two- (and three-)dimensional chromatograms associated to this technique. However, the simple eye inspection of these contour plots is frequently not enough to retrieve the desired information and the use of chemometry based approaches is often mandatory. The same applies for the quantitative analytical aspects where special attention will be paid to quality assurance and quality control of the GC ?e GC data. Recent achievements in these fields will be summarized in two chapters devoted to data acquisition and data treatment, and chemometric approaches, respectively.The last chapter in this part of the book will focus on recently introduced alternative couplings involving GC x GC which will eventually contribute to expand the field of application of this successful and powerful separation technique to new research areas. Part II will provide an overview of the current state-of-the-art in several relevant application fields. The enhanced separation provided by GC x GC has been demonstrated to be a distinctive benefice as compared to other available analytical techniques when dealing with the analysis of complex real-life extracts, irrespective of the goal of the analysis, i.e. group-type separation and fingerprinting, target-compound analysis, or identification of unknowns. The potential and versatility of GC x GC will be illustrate through a discussion of achievements in the analysis of petrochemicals, air and aerosols, essential oils and fragrances and pollutants in environmental samples. The selected examples will illustrate how the various technical and instrumentation developments discussed in Part I have been implemented in real-life analysis and are contributing to expand the application of GC x GC to new fields, including food analysis, identification of biomarkers and metabolomics. The potential of GC x GC in these fields will be discussed in detail in six separate chapters that will include the following points:- Â¡Â§IntroductionÂ¡Â¨ to define the main analytical goals intended in the selected research area, the target compounds and the analytical problems encountered in real-life analysis. It will also include a brief critical evaluation of alternative analytical techniques nowadays available for the intended determination as compared to GC x GC.- Â¡Â§State-of-the-artÂ¡Â¨ to describe the different GC x GC approaches developed depending on the aim of the analysis (or the group of analytes studied) summarizing and discussing their relative merits via representative real-life examples. This section will be the most extensive and largely treated since it is the main subject of this part of the book and different subsections will be defined depending on the topic revised. When required, e.g. in chapters dealing with the analysis of volatile compounds and pollutants, special analytical approaches, such as those involving the determination of enantiomers of chiral compounds, will also be discussed. In these cases, currently used GC x GC approaches will be critically compared with those involving alternative multidimensional gas chromatography-based approaches.- Â¡Â§QC/QAÂ¡Â¨ to discuss, when applicable, relevant analytical data reported for the applications revised in the previous section.- Â¡Â§Future trendsÂ¡Â¨ to provide an outlook on other possible studies and applications and, when applicable, will highlight the main remaining shortcomings and desirable technical improvements for further development.- Â¡Â§ReferencesÂ¡Â¨.The proposed book will have idiosyncratic features that should make it interesting to read, such as organized and complete description of the basic concepts and principles of the technique, their more relevant theoretical aspects, explanations on the last technical and instrumental implementations and reviews describing and discussing both the more common GC x GC working modes and those adopted for particular applications within a variety of research areas, and descriptions of future trends. Another unique attribute will be that it will offer practical and immediately applicable information on all major topics and application fields and, therefore, on a large variety of compounds, including hydrocarbons, volatile compounds, essential oil and plant components, food components, halogenated and non-halogenated organic pollutants, pesticides, drugs, and biomarkers among others. In all instances, the book will focus on the analytical aspects of the technique and its comparison with other currently available multidimensional gas chromatographic-based analytical strategies and will present the latest data accessible.