Analytical Supercritical Fluid Extraction, Softcover reprint of the original 1st ed. 1994

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.

1 Preliminary Operations of the Analytical Process.- 1.1 Analytical Chemistry Today.- 1.2 The Analytical Process.- 1.3 Preliminary Operations of the Analytical Process.- 1.3.1 Basic Features.- 1.3.2 Most Common Steps.- 1.3.3 Recent Developments.- 1.4 Analytical Separation Techniques.- 1.4.1 Objectives.- 1.4.2 Classifications.- 1.4.3 Continuous Separation Techniques.- 1.5 Extraction Systems in Analytical Chemistry.- 1.6 Analytical Leaching Methodologies.- 1.7 Ideal Features of an Analytical Leaching System.- 1.8 Supercritical Fluids and Analytical Chemistry.- References.- 2 Physico — Chemical Properties of Supercritical Fluids.- 2.1 Definition of Supercritical Fluid.- 2.2 Physical Properties of Supercritical Fluids.- 2.2.1 Properties at or near the Critical Point.- 2.2.2 Properties of the Supercritical Region.- 2.2.2.1 Density.- 2.2.22 Diffusivity.- 2.2.2.3 Viscosity.- 2.2.2.4 Dielectric Constant.- 2.3 Binary Systems.- 2.4 Polarity.- 2.4.1 The ?* Polarizability/Polarity Scale.- 2.5 Reactions in or with Supercritical Fluids.- 2.5.1 Reactions in Supercritical Fluids.- 2.5.1.1 Influence of Pressure on the Reaction Rate.- 2.5.1.2 Catalytic Effects.- 2.5.1.3 Supercritical Water as an Exceptional Reaction Medium.- 2.5.1.4 Enzymatic Reactions in Supercritical Fluids.- 2.5.2 Reactions with Supercritical Fluids.- 2.6 Other Properties of Supercritical Fluids.- 2.7 General Applications of Supercritical Fluids.- 2.7.1 Industrial Processes.- 2.7.1.1 Supercritical Fluids in the Food Industry.- 2.7.1.2 Polymer Processing with Supercritical Fluids.- 2.7.2 Processing of Heavy Hydrocarbons.- 2.7.3 Analytical Applications of Supercritical Fluids.- 2.7.4 Waste Detoxification with Supercritical Fluids.- 2.7.5 Other Applications of Supercritical Fluids.- References.- 3 Theoretical and Practical Aspects of Supercritical Fluid Extraction.- 3.1 Introduction.- 3.2 Foundation of Leaching.- 3.3 Purity of Supercritical Fluids.- 3.4 Solubility in Supercritical Fluids.- 3.4.1 Solubility Measurements in Supercritical Fluids.- 3.4.2 Solubility and Chemical Structure.- 3.4.2.1 Hydrocarbons.- 3.4.2.2 Hydroxyl Compounds.- 3.4.2.3 Carboxylic Acids.- 3.4.2.4 Ethers.- 3.4.2.5 Esters.- 3.4.2.6 Aldehydes.- 3.4.2.7 Nitrogen-Containing Compounds.- 3.4.3 The Solubility Parameter.- 3.4.4 Theoretical Models.- 3.4.5 Influence of Cosolvents on Solubility: the Entrainer Effect.- 3.4.5.1 Clustering.- 3.4.5.2 Effect of the Cosolvent on Selectivity.- 3.4.6 Entrainer Effect of a Second Solute.- 3.4.7 Solubility near a UCEP.- 3.5 Transport Phenomena.- 3.5.1 Desorption of Adsorbed Species.- 3.5.2 Diffusion in the Solid.- 3.5.2.1 The Spherical Model.- 3.5.2.2 The Infinite Slab Model.- 3.6 Factors Influencing Supercritical Leaching.- 3.6.1 Properties of the Supercritical Fluid.- 3.6.2 Properties of the Solid.- 3.6.3 Properties of the Solute.- 3.6.4 Presence of a Modifier.- 3.6.5 Additives.- 3.6.6 Derivatization.- 3.6.7 Temperature.- 3.6.8 Dynamic Factors.- References.- 4 The Analytical-Scale Supercritical Fluid Extractor.- 4.1 Introduction.- 4.2 The Supercritical Fluid Extractor: A Broad View.- 4.3 Basic Elements of a Supercritical Fluid Extractor.- 4.3.1 The Fluid Reservoir.- 4.3.1.1 Description.- 4.3.1.2 Connection to the Extractor.- 4.3.1.3 Functioning, Cautions.- 4.3.1.4 Measurement of the Cylinder Contents.- 4.3.2 The propulsion system.- 4.3.2.1 Single Systems.- 4.3.2.2 The Need for a Dual Propulsion System: Use of Modifiers.- 4.3.3 The Extraction Chamber.- 4.3.3.1 General Features.- 4.3.3.2 Cell Size.- 4.3.3.3 Sample Size to Cell Volume Ratio.- 4.3.3.4 Cell Geometry.- 4.3.3.5 Special Cells.- 4.3.3.6 Multi-Extraction Systems.- 4.3.3.7 Performance of Extraction Chambers.- 4.3.4 The Depressurization System.- 4.3.4.1 Types of Restrictors.- 4.3.4.2 Problems Arising from Depressurization.- 4.3.5 Collection Systems.- 4.3.5.1 Types.- 4.3.5.2 Special Collection Systems.- 4.3.6 Thermostating.- 4.3.7 Ancillary Components.- 4.4 Extraction Modes.- 4.5 Off-Line Coupled SF Extraction/Detection.- 4.6 On-Line Coupled SF Extraction/Detection.- 4.6.1 Types of Interfaces Used.- 4.6.2 Coupled SFE/Gas Chromatography.- 4.6.3 Coupled SFE/SFC.- 4.6.4 Coupled SFE/HPLC.- 4.6.5 Comparison of SFE Hyphenated Techniques with GC, SFC and HPLC.- 4.6.6 Other Hyphenated Techniques.- 4.7 Comparison of the Off-Line and On-Line Modes.- 4.8 Commercially Available Supercritical Fluid Extractors.- References.- 5 Analytical Applications of Supercritical Fluid Extraction.- 5.1 Introduction.- 5.2 Variables Affecting Extraction Quality.- 5.2.1 Nature and Composition of the Extractant.- 5.2.2 Pressure.- 5.2.3 Temperature.- 5.2.4 Flow-Rate.- 5.2.5 Extraction Time.- 5.2.6 Sample and Analyte Properties.- 5.2.7 Collection Systems.- 5.2.8 In-situ Derivatization.- 5.2.9 Other Factors.- 5.2.10 Quality Parameters.- 5.3 Sequential Extractions.- 5.4 General Applications of SFE.- 5.4.1 Types of Samples.- 5.4.1.1 Solid Samples.- 5.4.1.2 Liquid Samples.- 5.4.1.3 Gaseous Samples.- 5.4.1.4 Sample Size.- 5.4.2 Types of Analytes.- 5.4.3 Scope of Application of SFE.- 5.5 SFE and Other Extraction Techniques.- 5.5.1 Advantages of Supercritical Fluid Extraction.- 5.5.2 Disadvantages of Supercritical Fluid Extraction.- 5.6 Trends in SFE.- References.