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Recent advances in analytical chemistry have turned it into a virtually unrecognizable science compared to a few decades ago, when it lagged behind other sciences and techniques. However, advances in analytical science have been far from universal: while innovations in instrumentation and data acquisition and processing systems have reached unprecedented levels thanks to parallel breakthroughs in computer science and chemo metrics, progress in preliminary operations has been much slower despite their importance to analytical results. Thus, such clear trends in analytical process development as automation and miniaturization have not reached preliminary operations to the same extent, even though this area is pro bably in the greatest need. Improvement in preliminary operations is thus an urgent goal of analytical chemistry on the verge of the twenty first century. Increased R&D endeavours and manufacture of commercially available automatic equipment for implementation of the wide variety of operations that separate the uncollected, unmeasured, untreated sample from the signal measuring step are thus crucial on account of the wide variability of such operations, which precludes development of all-purpose equipment, and the complexity of some, particularly relating to solid samples. Supercritical fluid extraction opens up interesting prospects in this context and is no doubt an effective approach to automatioI1 and mini aturization in the preliminary steps of the analytical process. The dramatic developments achieved in its short life are atypical in many respects.
The use of supercritical fluids in analytical chemistry is still grow ing. More and more analysts are discovering the favorable advan tages for a number of applications. Especially supercritical fluid extraction (SFE) has attracted a lot of interest in recent years due to its simplicity. Supercritical fluid chromatography (SFC) has become better established and the development of this technique has been accelerated by the many applications with capillary col umns which have been published in the literature. At first SFC equipment was based on instruments commonly used for liquid chromatography, and the first commercial in struments were derived from this technology. However, capillary columns can be much more easily interfaced to gas chromatogra phy equipment especially to the detectors commonly used for Oc. Many stationary phases both for packed micro columns and capillary columns have been designed for SFC purposes extending this technology to LC and OC. The most common fluid applied in SFC and SFE is carbon dioxide. The advantages of supercritical CO , such as having dif 2 fusivity like a gas and solvating power depending on temperature and pressure, are also valid for other fluids and modified fluids. Both properties are valuable for sample extraction and extraction selectivity.
The continued search for rapid, efficient and cost-effective means of analytical measurement has introduced supercritical fluids into the field of analytical chemistry. Two areas are common: supercritical fluid chroma tography and supercritical fluid extraction. Both seek to exploit the unique properties of a gas at temperatures and pressures above the critical point. The most common supercritical fluid is carbon dioxide, employed because of its low critical temperature (31 °C), inertness, purity, non-toxicity and cheapness. Alternative supercritical fluids are also used and often in conjunction with modifiers. The combined gas-like mass transfer and liquid-like solvating characteristics have been used for improved chroma tographic separation and faster sample preparation. Supercritical fluid chromatography (SFC) is complementary to gas chro matography ( GC) and high performance liquid chromatography (HPLC), providing higher efficiency than HPLC, together with the ability to analyse thermally labile and high molecular weight analytes. Both packed and open tubular columns can be employed, providing the capability to analyse a wide range of sample types. In addition, flame ionization detection can be used, thus providing 'universal' detection.
During the past decade supercritical fluid extration (SFE) has attracted considerable attention as a sample preparation procedure in analytical chemistry. The successful implementation of this technique can lead to improved sample throughput, more efficient recovery of analytes, cleaner extracts, economic replacement of halogenated solvents and a high level of automation, compared to conventional sample preparation procedures. This book provides an overview of basic principles of SFE as well as in-depth reviews of both on- and off-line SFE methods. The on-line coupling of SFE with both chromatographic and spectroscopics techniques has been the subject of a great deal of research effort and is dealt with in detail. Newer developments, such as off-line SFE of solid and liquid matrices, are starting to attract a great deal of interest, and the coverage of these areas will prove of particular value to the analytical chemist. The international team of authors has illustrated these topics with many `state-of-the-art' applications, and each chapter provides a comprehensive list of references. For the convenience of the reader, an appendix which contains pressure conversion scales and supercritical fluid carbon dioxide density tables appears at the end of the book. The volume's extensive coverage of both on-line and off-line extraction will be particularly useful to analytical chemists, in a wide range of environments, seeking to develop high quality, simple and robust SFE methods.
by Professor D. E. Games, Mass Spectrometry Research Unit, University College of Swansea Sample preparation can be viewed as occupying a Cinderella role in analytical science. However, the quality of sample preparation plays a key role in high In the past decade, there has been quality analysis and deserves higher stature. considerable interest in the use of supercritical fluid extraction (SFE) as an alternative to conventional procedures for the preparation of samples for ana lysis. The driving force for this development is the need for automated, sim pler, faster, non-destructive and selective methods for extraction, preferably using non-toxic extraction media which are easily disposed of. Utilization of supercritical fluids for extraction fulfils these requirements because of their unique physical chemical properties and usually low toxicity. Selectivity can be achieved by suitable selection of pressure (density), temperature and modi fier conditions which enable solvating power to be varied. The high diffusivity of supercritical fluids provides rapid sample penetration and extraction. Use of fluids with low critical temperatures enables extraction to be conducted under mild thermal conditions ensuring that thermally labile compounds do not decompose. The technique can be used off-line, and the extracts analysed by appropriate techniques, or it can be used on-line, by coupling with a variety of chromatographic techniques. These can then, if necessary, be coupled fur ther with spectroscopic techniques, such as Fourier transform infrared, ultra violet or mass spectrometry, to provide specific identification or structural information.
Enhanced concern for the quality and safety of food products, increased preference for natural products, and stricter regulations on the residual level of solvents, all contribute to the growing use of supercritical fluid technology as a primary alternative for the extraction, fractionation, and isolation of active ingredients. As a solvent-free p
Supercritical fluids are neither gas nor liquid, but can be compressed gradually from low to high density and they are therefore interesting and important as tunable solvents and reaction media in the chemical process industry. By adjusting the density the properties of these fluids can be customised and manipulated for a given process - physical or chemical transformation. Separation and processing using supercritical solvents such as CO2 are currently on-line commercially in the food, essential oils and polymer industries. Many agencies and industries are considering the use of supercritical water for waste remediation. Supercritical fluid chromatography represents another, major analytical application. Significant advances have recently been made in materials processing, ranging from particle formation to the creation of porous materials. The chapters in this book provide tutorial accounts of topical areas centred around: (1) phase equilibria, thermodynamics and equations of state; (2) critical behaviour, crossover effects; (3) transport and interfacial properties; (4) molecular modelling, computer simulation; (5) reactions, spectroscopy; (6) phase separation kinetics; (7) extractions; (8) applications to polymers, pharmaceuticals, natural materials and chromatography; (9) process scale-up.
This book contains papers from the symposium "Critical Issues, Current and Emerging Technologies for Determination of Crude Fat Content in Food, Feed and Seeds," held in 2003 at the AOCS Annual Meeting in Kansas City, Missouri. The topics covered give a broad perspective of the challenges and issues of the value-added enhanced products. This book w
The relatively new technique of solid phase microextraction (SPME) is an important tool to prepare samples both in the lab and on-site. SPME is a "green" technology because it eliminates organic solvents from analytical laboratory and can be used in environmental, food and fragrance, and forensic and drug analysis. This handbook offers a thorough background of the theory and practical implementation of SPME. SPME protocols are presented outlining each stage of the method and providing useful tips and potential pitfalls. In addition, devices and fiber coatings, automated SPME systems, SPME method development, and In Vivo applications are discussed. This handbook is essential for its discussion of the latest SPME developments as well as its in depth information on the history, theory, and practical application of the method. - Practical application of Solid Phase Microextraction methods including detailed steps - Provides history of extraction methods to better understand the process - Suitable for all levels, from beginning student to experienced practitioner
A thorough introduction to environmental monitoring in the oil and gas industry Analytical Techniques in the Oil and Gas Industry for Environmental Monitoring examines the analytical side of the oil and gas industry as it also provides an overall introduction to the industry. You’ll discover how oil and natural gas are sourced, refined, and processed. You can learn about what’s produced from oil and natural gas, and why evaluating these sourced resources is important. The book discusses the conventional analyses for oil and natural gas feeds, along with their limitations. It offers detailed descriptions of advanced analytical techniques that are commercially available, plus explanations of gas and oil industry equipment and instrumentation. You’ll find technique descriptions supplemented with a list of references as well as with real-life application examples. With this book as a reference, you can prepare to apply specific analytical methods in your organization’s lab environment. Analytical Techniques can also serve as your comprehensive resource on key techniques in the characterization of oil and gas samples, within both refinery and environmental contexts. Understand of the scope of oil and gas industry techniques available Consider the benefits and limitations of each available process Prepare for applying analytical techniques in your lab See real examples and a list of references for each technique Read descriptions of off-line analytics, as well as on-line and process applications As a chemist, engineer, instructor, or student, this book will also expand your awareness of the role these techniques have in environmental monitoring and environmental impact assessments.