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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.

Inhaltsverzeichnis

Frontmatter

1. Preliminary Operations of the Analytical Process

Abstract
Information is central to today’s society and modern economy. Inasmuch as analytical chemistry is the chemical metrological science, it obviously plays a prominent role in this respect [1]. Delivery of analytical results and their interpretation make two cornerstones on which correct, well-founded decisions should rest. Some estimates suggest that between 5 and 6% of the gross domestic product of developed countries is expended on chemical measurements. Denying the significance of analytical chemistry can only be the result of a manifest lack of knowledge or unscientific interests.
Maria Dolores Luque de Castro, Miguel Valcárcel, Maria Teresa Tena

2. Physico — Chemical Properties of Supercritical Fluids

Abstract
A supercritical fluid (SF) is a state where matter is compressible and behaves as a gas (i.e. it fills and takes the shape of its container), which is not the case when it is in a liquid state (an incompressible fluid that occupies the bottom of its container). However, a supercritical fluid has the typical density of a liquid (between 0.1 and l.0g/ml) and hence its characteristic dissolving power. Finally, an SF can also be defined as a heavy gas with a controllable dissolving power or as a form of matter in which the liquid and gaseous state are indistinguishable.
Maria Dolores Luque de Castro, Miguel Valcárcel, Maria Teresa Tena

3. Theoretical and Practical Aspects of Supercritical Fluid Extraction

Abstract
In Chap. 1, leaching was defined as a solid-liquid separation process whereby the analytes of interest in a solid sample are extracted by means of a condensed liquid or supercritical fluid, whether organic or inorganic. The most salient properties and functions of supercritical fluids were described in Chap. 2. This Chapter is devoted to describing in a broad sense the theoretical and practical aspects of supercritical fluid (SF) leaching (extraction). In this context, the purity and affordability of SFs typically used in analytical applications are discussed first. Next, two essential elements that are central to the extraction process are examined, viz. analyte dissolution and transport phenomena, in terms of both the way they are influenced by various experimental factors and the physicochemical parameters usually employed to characterize them. Finally, factors affecting supercritical leaching are reviewed in groups according to whether they influence the supercritical fluid, the solid sample, the solute- analyte, the working conditions or modifier systems (with or without derivatization). A more detailed description of the development and applications of supercritical fluids for analytical purposes is provided in Chap. 4, devoted to extractors and operational modes, and Chap. 5 is concerned with the features and applications of SFE.
Maria Dolores Luque de Castro, Miguel Valcárcel, Maria Teresa Tena

4. The Analytical-Scale Supercritical Fluid Extractor

Abstract
Chapter 1 is concerned with supercritical fluid extraction (SFE) in terms of the analytical process, with emphasis on the significance of its preliminary operations. Chapter 2 describes the physico-chemical properties of supercritical fluids and reviews their applications. Finally, Chapter 3 deals in systematic fashion with solid-supercritical fluid extraction (leaching) and the most influential factors on its efficiency, throughput and selectivity.
Maria Dolores Luque de Castro, Miguel Valcárcel, Maria Teresa Tena

5. Analytical Applications of Supercritical Fluid Extraction

Abstract
The high throughput and versatility of SFE usually leads novices to undertake short, isolated studies rather than systematic development of specific applications, which sooner or later results in the appearance of unexpected problems. Supercritical fluid extraction is a recent, still fairly unexplored technique that must be consolidated with the rigour exercised in developing other analytical methodologies.
Maria Dolores Luque de Castro, Miguel Valcárcel, Maria Teresa Tena

Backmatter

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