Analytical Supercritical Fluid Extraction PDF
Preview Analytical Supercritical Fluid Extraction
SPRINGER LAB MANUAL M.D. Luque de Castro M. Valcarcel M.T. Tena Analytical Supercritical Fluid Extraction With 180 Figures Springer-Verlag Berlin Heidelberg New York London Paris Tokyo Hong Kong Barcelona Budapest Professor MARIA DOLORES LUQUE DE CASTRO Professor Dr. MIGUEL V ALCARCEL Dr. MARIA TERESA TENA University of Cordoba Department of Analytical Chemistry Avda. San Alberto Magno, sin E-14004 Cordoba Spain ISBN-13: 978-3-642-78675-4 e-ISBN-13: 978-3-642-78673-0 DOl: 10.107/978-3-642-78673-0 Library of Congress Cataloging~in-Puhlication Data. ValcarccJ Cases, Miguel. Analytical supercritical fluid extraction I M. Valeareel, M.D. Luque de Castro, M.T. Tena. p. em. - (Springer laboratory) Includes bibliographical references. ISBN·I3: 978-3-642-78675-4 1. Supercritical fluid extraction. I. Luque de Castro, M.D. II. Tena, M.T. (Maria Teresa) III. Titl<. IV. Series. TP156.EBV2H 1994 S43'.089-de20 94-77gt This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned. specifically the rights of translation, reprinting reuse of illustrations, recitation, broadcasting. reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of Septemher 9, 1965, in its current version, and permissions for use must always he obtained from Springer-Verlag. Violations are liable for prosecution under the German Copyright Law. © Springer-Verlag Berlin Heidelberg 1994 Softeover reprint of the hardcover 1st edition 1994 The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the ahsence of a specific statement, that such names arc exempt from the relevant protective laws and regulations and therefore free for general use. Typesetting: Best-set Typesetter Ltd., Hong Kong 52/3130-54321-Printed on acid-free paper Preface 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. Thus, unlike other analytical alternatives, commercialization of SFE equipment has not been preceded by exhaustive R&D work; its chromatographic counterpart was developed in advance. The advantages of SFE over other solid-liquid extraction techniques make it particularly attractive for routine analyses of large numbers of solid samples. This book provides an overview of the state of the art in analytical-scale supercritical fluid extraction and its potential. Chapter 1 reviews the pre liminary operations of the analytical process and relates supercritical fluid extraction to them. The physico-chemical properties of the supercritical state (Chapter 2) and the fundamentals of supercritical fluid extraction (Chapter 3) make obvious stepping-stones to a comprehensive description of the SF extractor (Chapter 4) and selected applications and trends of SFE techniques (Chapter 5). Supercritical fluid extraction is doubtless of VI Preface interest to all analytical laboratories concerned with the analysis of solid samples, as well as to teachers of chemical analysis. No doubt, the SFE technique has a promising future that will come with the spread of its high potential for solving analytical problems, to which this book is essentially devoted. The authors should like to thank Springer-Verlag for their warm welcome for the book, Antonio Losada for translation of the Spanish manuscript, and Jose Manuel Membrives and Francisco Doctor for pro ducing the artwork. Cordoba, May 1994 M.D. LUQUE DE CASTRO M. V ALCARCEL M.T. TENA Contents 1 Preliminary Operations of the Analytical Process . . . . . . . . 1 1.1 Analytical Chemistry Today. . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 The Analytical Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.3 Preliminary Operations of the Analytical Process. . . . . . . . 3 1.3.1 Basic Features........ . ............................ 4 1.3.2 Most Common Steps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.3.3 Recent Developments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.4 Analytical Separation Techniques. . . . . . . . . . . . . . . . . . . . . 11 1.4.1 Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.4.2 Classifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.4.3 Continuous Separation Techniques. . . . . . . . . . . . . . . . . . . . 15 1.5 Extraction Systems in Analytical Chemistry ............ 16 1.6 Analytical Leaching Methodologies . . . . . . . . . . . . . . . . . . . 19 1. 7 Ideal Features of an Analytical Leaching System. . . . . . . . 25 1.8 Supercritical Fluids and Analytical Chemistry. . . . . . . . . . . 27 References ................................................ 30 2 Physico-Chemical Properties of Supercritical Fluids .... . 32 2.1 Definition of Supercritical Fluid ..................... . 32 2.2 Physical Properties of Supercritical Fluids ............. . 37 2.2.1 Properties at or near the Critical Point ................ . 37 2.2.2 Properties of the Supercritical Region ................ . 40 2.2.2.1 Density .......................................... . 42 2.2.2.2 Diffusivity ........................................ . 44 2.2.2.3 Viscosity ......................................... . 45 2.2.2.4 Dielectric Constant ................................ . 46 2.3 Binary Systems .................................... . 48 2.4 Polarity .......................................... . 53 2.4.1 The rc* Polarizability/Polarity Scale .................. . 53 2.5 Reactions in or with Supercritical Fluids .............. . 57 2.5.1 Reactions in Supercritical Fluids ..................... . 57 2.5.1.1 Influence of Pressure on the Reaction Rate ............ . 57 2.5.1.2 Catalytic Effects ................................... . 59 2.5.1.3 Supercritical Water as an Exceptional Reaction Medium .......................................... . 61 VIII Contents 2.5.1.4 Enzymatic Reactions in Supercritical Fluids. . . . . . . . . . . . 61 2.5.2 Reactions with Supercritical Fluids. . . . . . . . . . . . . . . . . . . . 63 2.6 Other Properties of Supercritical Fluids. . . . . . . . . . . . . . . . 65 2.7 General Applications of Supercritical Fluids. . . . . . . . . . . . 67 2.7.1 Industrial Processes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 2.7.1.1 Supercritical Fluids in the Food Industry. . . . . . . . . . . . . . . 70 2.7.1.2 Polymer Processing with Supercritical Fluids ........... 72 2.7.2 Processing of Heavy Hydrocarbons. . . . . . . . . . . . . . . . . . . . 73 2.7.3 Analytical Applications of Supercritical Fluids. . . . . . . . . . 74 2.7.4 Waste Detoxification with Supercritical Fluids. . . . . . . . . . 75 2.7.5 Other Applications of Supercritical Fluids. . . . . . . . . . . . . . 75 References ......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 3 Theoretical and Practical Aspects of Supercritical Fluid Extraction ..................... . 79 3.1 Introduction ...................................... . 79 3.2 Foundation of Leaching ............................ . 79 3.3 Purity of Supercritical Fluids ........................ . 81 3.4 Solubility in Supercritical Fluids ..................... . 88 3.4.1 Solubility Measurements in Supercritical Fluids ........ . 92 3.4.2 Solubility and Chemical Structure .................... . 93 3.4.2.1 Hydrocarbons ..................................... . 96 3.4.2.2 Hydroxyl Compounds .............................. . 97 3.4.2.3 Carboxylic Acids .................................. . 98 3.4.2.4 Ethers ........................................... . 98 3.4.2.5 Esters ............................................ . 99 3.4.2.6 Aldehydes ............................. , .......... . 99 3.4.2.7 Nitrogen-Containing Compounds .................... . 99 3.4.3 The Solubility Parameter ........................... . 100 3.4.4 Theoretical Models ................................ . 108 3.4.5 Influence of Cosolvents on Solubility: the Entrainer Effect ................................ . 110 3.4.5.1 Clustering ........................................ . 116 3.4.5.2 Effect of the Cosolvent on Selectivity ................. . 118 3.4.6 Entrainer Effect of a Second Solute .................. . 119 3.4.7 Solubility near a VCEP ............................. . 121 3.5 Transport Phenomena .............................. . 123 3.5.1 Desorption of Adsorbed Species ..................... . 125 3.5.2 Diffusion in the Solid .............................. . 127 3.5.2.1 The Spherical Model ............................... . 127 3.5.2.2 The Infinite Slab Model ............................ . 131 3.6 Factors Influencing Supercritical Leaching ............ . 132 3.6.1 Properties of the Supercritical Fluid .................. . 134 Contents IX 3.6.2 Properties of the Solid. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 3.6.3 Properties of the Solute ............................. 142 3.6.4 Presence of a Modifier .............................. 145 3.6.5 Additives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 3.6.6 Derivatization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 3.6.7 Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 3.6.8 Dynamic Factors ................................... 163 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 4 The Analytical-Scale Supercritical Fluid Extractor ...... . 169 4.1 Introduction ...................................... . 169 4.2 The Supercritical Fluid Extractor: A Broad View ...... . 169 4.3 Basic Elements of a Supercritical Fluid Extractor ....... . 171 4.3.1 The Fluid Reservoir ................................ . 171 4.3.1.1 Description ....................................... . 171 4.3.1.2 Connection to the Extractor ......................... . 173 4.3.1.3 Functioning, Cautions .............................. . 175 4.3.1.4 Measurement of the Cylinder Contents ............... . 175 4.3.2 The propulsion system ............................. . 176 4.3.2.1 Single Systems .................................... . 176 4.3.2.2 The Need for a Dual Propulsion System: Use of Modifiers .................................. . 178 4.3.3 The Extraction Chamber ........................... . 180 4.3.3.1 General Features .................................. . 180 4.3.3.2 Cell Size ......................................... . 180 4.3.3.3 Sample Size to Cell Volume Ratio ................... . 181 4.3.3.4 Cell Geometry .................................... . 182 4.3.3.5 Special Cells ...................................... . 183 4.3.3.6 Multi-Extraction Systems ........................... . 185 4.3.3.7 Performance of Extraction Chambers ................. . 187 4.3.4 The Depressurization System ........................ . 187 4.3.4.1 Types of Restrictors ................................ . 188 4.3.4.2 Problems Arising from Depressurization .............. . 190 4.3.5 Collection Systems ................................. . 193 4.3.5.1 Types ............................................ . 193 4.3.5.2 Special Collection Systems .......................... . 201 4.3.6 Thermostating .................................... . 201 4.3.7 Ancillary Components ............................. . 203 4.4 Extraction Modes ................................. . 204 4.5 Off-Line Coupled SF Extraction/Detection ............ . 206 4.6 On-Line Coupled SF Extraction/Detection ............ . 211 4.6.1 Types of Interfaces Used ........................... . 211 4.6.2 Coupled SFE/Gas Chromatography .................. . 216 X Contents 4.6.3 Coupled SFE/SFC ................................. . 220 4.6.4 Coupled SFE/HPLC ............................... . 225 4.6.5 Comparison of SFE Hyphenated Techniques with GC, SFC and HPLC ........................... . 227 4.6.6 Other Hyphenated Techniques ...................... . 228 4.7 Comparison of the Off-Line and On-Line Modes ....... . 233 4.8 Commercially Available Supercritical Fluid Extractors .. . 236 References ............................................... . 242 5 Analytical Applications of Supercritical Fluid Extraction .. 244 5.1 Introduction ...................................... . 244 5.2 Variables Affecting Extraction Quality ............... . 245 5.2.1 Nature and Composition of the Extractant ............ . 248 5.2.2 Pressure .......................................... . 249 5.2.3 Temperature ...................................... . 251 5.2.4 Flow-Rate ........................................ . 251 5.2.5 Extraction Time ................................... . 252 5.2.6 Sample and Analyte Properties ...................... . 254 5.2.7 Collection Systems ................................. . 260 5.2.8 In-situ Derivatization .............................. . 260 5.2.9 Other Factors ..................................... . 263 5.2.10 Quality Parameters ................................ . 265 5.3 Sequential Extractions ............................. . 269 5.4 General Applications of SFE ........................ . 273 5.4.1 Types of Samples .................................. . 274 5.4.1.1 Solid Samples ..................................... . 287 5.4.1.2 Liquid Samples .................................... . 288 5.4.1.3 Gaseous Samples .................................. . 290 5.4.1.4 Sample Size ....................................... . 292 5.4.2 Types of Analytes ................................. . 293 5.4.3 Scope of Application of SFE ........................ . 295 5.5 SFE and Other Extraction Techniques ................ . 297 5.5.1 Advantages of Supercritical Fluid Extraction .......... . 298 5.5.2 Disadvantages of Supercritical Fluid Extraction ........ . 304 5.6 Trends in SFE .................................... . 305 References ............................................... . 309 Subject Index ............................................. . 313 1 Preliminary Operations of the Analytical Process 1.1 Analytical Chemistry Today 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. Analytical chemistry must meet the challenges posed by society on the verge of the twenty first century, a continuously developing society requir ing this science to adjust itself to advances in other scientific and technical areas. The primary goals of current analytical chemistry can be summed up as the obtaining of greater amounts of chemical information of a higher quality on any type of material or system studied by using increasingly less material, time and human resources, taking the lowest hazards and incurring the lowest expenses. For analytical chemistry to accomplish these generic goals, it must include three major constituents, namely (a) research and development, (b) the suite of analytical methods and tech niques that make up what was formerly called chemical analysis; and (c) education. This in turn entails the existence of two branches, basic and applied analytical chemistry, which must bear appropriate relationships to each other and the rest of the diverse scientific and technical areas [2]. Automation and miniaturization [3] are two solidly established trends Automation in science and technology with an undeniable effect on current break- and throughs in analytical chemistry. Few analytical innovations involve neither miniaturization as they respond to decreased material, time and human resource ex- penditure and diminished hazards. On the other hand, the impressive development of analytical instrumentation and massive use of (micro)- computers in the laboratory has facilitated the obtaining of more analytical information of a higher quality.
The list of books you might like
