Analysis with Supercritical Fluids: Extraction and Chromatography

224 Pages·1992·9.583 MB·English

by  Bernd Wenclawiak (auth.), Professor Dr. Bernd Wenclawiak (eds.)

SPRINGER
LABORATORY
Bernd Wenclawiak (Ed.)
Analysis with
Supercritical Fluids:
Extraction and
Chromatography
With 117 Figures
Springer-Verlag
Berlin Heidelberg New York London Paris
Tokyo Hong Kong Barcelona Budapest
Professor Dr. BERND WENCLAWIAK
Universitat-GH Siegen
Fachbereich 8
Analytische Chemie I
Adolf-Reichwein-StraBe
W-5900 Siegen, FRG
ISBN-13: 978-3-642-77476-8 e-ISBN-13: 978-3-642-77474-4
DOl: 10.1007/978-3-642-77474-4
Library of Congress Cataloging-in-Publication Data. Wenclawiak, Bernd. Analysis with super
critical fluids: extraction and chromatography, Bernd Wenclawiak. p. cm. Includes
bibliographical references and index. ISBN 3-540-55420-3 (Springer-Verlag Berlin Heidelberg
New York: acid-free paper): DM 148.00. - ISBN 0-387-55420-3 (Springer-Verlag New York
Berlin Heidelberg: acid-free paper) 1. Supercritical fluid chromatography. 2. Supercritical fluid
extraction. 1. Title. QD79.C45W46 1992 543'.089-dc20 92-18355
This work is subject to copyright. All rights are reserved, whether the whole or part of the ma
terial is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recita
tion, 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 September 9, 1965, in its current version, and permission for use
must always be obtained from Springer-Verlag. Violations are liable for prosecution under the
German Copyright Law.
© Springer-Verlag Berlin Heidelberg 1992
Sofleover reprint of the hardcover I st edition 1992
The use of general descriptive names, registered names, trademarks, etc. in this publication
does not imply, even in the absence of a specific statement, that such names are exempt from
the relevant protective laws and regulations and therefore free for general use.
Typesetting: K + V Fotosatz GmbH, Beerfelden
52/3145-5 4 3 2 1 0 - Printed on acid-free paper
Preface
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 CO2, such as having dif
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 link between much engineering research work and analyti
cal chemistry research is still weak. Much can be learned from
both fields. As soon as more standard procedures will allow or ask
for the use of supercritical fluids, especially carbon dioxide, many
chemists will apply them. Instrument manufacturers are working
hard to fulfill the expectations and requirements of many scien
tists. Supercritical fluid chromatography has become established
as an alternative and the missing link between liquid chromatogra
phy'and gas chromatography. What can be expected from SFE? It
is conquering the analytical laboratory and is competing with stan
dard procedures. As soon as automatic instrumentation with high
sample capacity becomes available, it will become the standard
procedure for sample preparation of many substances.
This book contains articles collected over a period of 1 year
from various contributors whose efforts are outlined in the various
chapters. I have to thank all the authors for their work and time
to make this a sound undertaking.
VI Preface
My thanks go also to H. Steuber for typing and retyping many
of the manuscripts and to D. Winkel for working on some figures,
also to the publisher and to all of those who patiently supported
my project.
Siegen, August 1992 BERND WENCLAWIAK
Contents
1 SFC and SFE: An Introduction for Novices
BERND WENCLAWIAK ............................... 1
2 Physico-chemical Principles
of Supercritical Fluid Separation Processes
GERHARD M. SCHNEIDER ... . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1 Introduction ................................ . 9
2.2 Physico-chemical Properties
of Pure Supercritical Solvents ................. . 10
2.2.1 Thermodynamic Properties ................... . 10
2.2.2 Dielectric Properties ......................... . 10
2.2.3 Transport Properties ......................... . 12
2.3 Phase Equilibria of Fluid Mixtures ............ . 13
2.3.1 Phase-Theoretical Aspects .................... . 13
2.3.2 Classification of Binary Critical Phase Behavior
by "Families" ............................... . 14
2.3.3 Ternary Systems ............................. . 16
2.3.4 Quaternary Systems ......................... . 19
2.3.5 Solubility of Solids in Supercritical Solvents .... . 21
2.3.6 Isothermal Pressure (Concentration)
Phase Diagrams ............................. . 21
2.3.7 Calculation and Correlation
of Fluid Phase Equilibria .................... . 24
2.4 Physico-chemical Applications of SFC ......... . 26
2.4.1 Capacity Ratios ............................. . 26
2.4.2 Diffusion Coefficients ....................... . 28
References ........................................ . 30
3 Basic Principles of Analytical Supercritical Fluid
Extraction
JERRY W. KING and JOHN E. FRANCE ................ . 32
3.1 The Development of Analytical SFE ........... . 32
3.1.1 Sample Preparation in Analytical Chemistry .... . 32
3.1.2 Utilization of Supercritical Fluids
in Analytical-Scale .Extractions ................ . 33
3.1.3 Features of Analytical SFE ................... . 33
VIII Contents
3.2 Fluid Properties in SFE ...................... . 34
3.2.1 Selection of the Supercritical Fluid ............ . 34
3.2.2 Unique Properties of Supercritical Fluid
Carbon Dioxide ............................. . 36
3.2.3 The Use of Cosolvents in SFE ................ . 37
3.3 Optimizing Experimental Conditions
for Analytical SFE .......................... . 39
3.3.1 Objectives of the Extraction .................. . 39
3.3.2 Critical Parameters Pertinent to SFE ........... . 41
3.3.3 A Theoretical Approach for Optimizing SFE ... . 42
3.4 The Relevance of SFC-Derived Data
to Analytical SFE ........................... . 43
3.4.1 Relevant Measurements by SFC ............... . 44
3.4.2 Implications for SFE ........................ . 45
3.5 The Practice of Analytical SFE ............... . 46
3.5.1 Equipment Requirements ..................... . 46
3.5.2 Experimental Considerations in Analytical SFE .. 49
3.6 Sample Matrix Effects in SFE ................ . 51
3.6.1 Physical Matrix Effects ...................... . 52
3.6.2 Chemical Changes in the Sample Matrix ....... . 52
3.6.3 . Impact of Matrix on Extraction Kinetics ....... . 53
3.7 Problems and Future Research Needs
in Analytical SFE ........................... . 55
References ......................................... 57
4 Coupled Supercritical Fluid Extraction-Capillary
Gas Chromatography (SFE-GC)
STEVEN B. HAWTHORNE............................. 61
4.1 Introduction ................................ . 61
4.2 Performing SFE-GC ......................... . 61
4.2.1 Instrumentation and Methods ................. . 61
4.2.2 Fluids and Extraction Conditions
Used for SFE-GC ........................... . 64
4.3 Abilities and Limitations of Split and On-Column
SFE-GC ................................... . 65
4.3.1 'Chromatographic Peak Shapes Obtained
Using SFE-GC .............................. . 65
4.3.2 Quantitation Using SFE-GC .................. . 67
4.3.3 Speed of SFE-GC Analyses ................... . 67
4.3.4 Sensitivity and Sample Sizes .................. . 68
4.3.5 Sample Types and Matrix Considerations ....... . 70
4.4 Summary .................................. . 72
References ......................................... 72
Contents IX
5 Gradients in SFC
ERNST KLESPER and FRANZ P. SCHMITZ. ... . .. . ..... .. 74
5.1 Overview ................................... . 74
5.2 Temperature Gradients ....................... . 79
5.3 Pressure Gradients 81
5.4 Density Gradients 87
5.5 Velocity Gradients 94
5.6 References .................... '. ............. . 97
6 Injection Techniques in SFC
TYGE GREIBROKK ................................... 100
6.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
6.2 The Physical State of the Sample. . . . . . . . . . . . . . . 100
6.3 Introduction of Supercritical Fluid Extracts ...... 100
6.4 Introducing a Solution ........................ 101
6.5 Peak Focusing ............................... 102
6.6 Direct Injection .............................. 103
6.7 Open Split (Dynamic Split) Injection ........... 103
6.8 Timed Split Injection ......................... 105
6.9 Solvent Effects on Peak Shape ................. 106
6.10 Solvent Venting with a Precolumn .............. 107
6.11 Solvent Backflush ............................ 109
6.12 Solvent Venting with Gas Purging .............. 111
6.13 Sample Losses in the Injector .................. 114
References ......................................... 115
7 Stationary Phases for Packed Column
Supercritical Fluid Chromatography
COLIN F. POOLE, JOHN W. OUDSEMA,
THOMAS A. DEAN, and SALWA K. POOLE 116
7.1, Introduction.... . .... . .. .... ... .... .... ... ... 116
7.2 Physical Properties of Column Packings ........ 116
7.3 Influence of Substrate Morphology on the
Properties of Chemically Bonded Phases in SFC 121
7.4 Influence of Surface Heterogeneity on the
Properties of Chemically Bonded Phases ........ 122
7.4.1 Chemical Interactions with Silanol Groups ...... 122
7.4.2 Deactivation of Silanol Groups
with Mobile Phase Modifiers .................. 124
X Contents
7.4.3 Shielding of Silanol Groups
by Polymer Encapsulation ..................... 126
7.5 Macroporous Polymeric Packings . . . . . . . . . . . . . .. 127
7.6 Column Packings Used for Special Applications . 127
7.7 Conclusions...... .... ........ ........ .... ... 131
References ......................................... 132
8 Enantiomer Separation by Capillary
Supercritical Fluid Chromab>graphy
MICHAEL SCHLEIMER and VOLKER SCHURIG 134
8.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
8.2 General Aspects .............................. 135
8.2.1 Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
8.2.2 Speed of Analysis and Efficiency ............... 136
8.2.3 Mobile Phase ................................ 138
8.2.4 Column Loadability .......................... 139
8.3 Packed Column SFC ......................... 140
8.4 Open Tubular Column SFC ........... , . . .... .. 140
8.5 Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . 146
References ........................................ . 149
9 Supercritical Fluid Chromatographyl
Mass Spectrometry
J. DAVID PINKSTON ................................ . 151
9.1 Introduction ................................ . 151
9.2 Early Investigations of SFC/MS .............. . 151
9.3 SFC/MS Using Direct Introduction Interfaces .. . 152
9.3.1 Flow Restriction ............................ . 153
9.3.2 Ionization Methods .......................... . 154
9.3.2.1 Chemical Ionization ......................... . 154
9.3.2.2 Electron Ionization and Charge Exchange ...... . 155
9.3.2.3 Secondary Ion Mass Spectrometry ............. . 156
9.3.3 J'ype of Mass Analyzer ...................... . 157
9.3.3.1 DFI SFC/MS Using Quadrupole
Mass Spectrometers .......................... . 157
9.3.3.2 DFI SFC/MS Using Double-Focussing
Sector Mass Spectrometers ................... . 158
9.3.3.3 DFI SFC/MS Using Fourier Transform
Mass Spectrometers .......................... . 158
9.4 SFC/MS Using High-Flow-Rate Interfaces ...... . 161
9.4.1 SFC/MS Using the Moving Belt Interface ...... . 162
9.4.2 SFC/MS Using the Particle Beam Interface ..... . 163
Contents XI
9.4.3 Off-line SFC/MS ............................ . 164
9.4.4 SFC/MS Using Direct Introduction
of Split Effluents ........................... . 164
9.4.5 SFC/MS Using Post-Expansion Splitting ....... . 165
9.4.6 SFC/MS Using the Thermospray Interface ..... . 170
9.5 Supercritical Fluid Injection/Mass Spectrometry .. 172
9.6 Conclusion ................................. . 174
References ........................................ . 175
10 Supercritical Fluid Chromatography
with FT-IR Detection
LARRY T. TAYLOR and ELIZABETH M. CALVEY 178
10.1 Introduction..... .. .. ................ . . ... ... 178
10.2 Flow Cell Approach .......................... 178
10.3 Solvent Elimination Approach ................. 184
10.4 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
References ......................................... 188
11 Supersonic Jet Spectroscopy with Supercritical Fluids
CHUNG HANG SIN, STEVEN R. GOATES, MILTON L. LEE,
and DAVID M. LUBMAN ............................. 190
11.1 Introduction ................................ . 190
11.2 Supersonic Jet Spectroscopy .................. . 191
11.2.1 Principles of Supersonic Expansions ........... . 191
11.2.2 Spectroscopic Methods for Detection .......... . 192
11.3 High Pressure Fluid Injection
for Nonvolatile Samples ...................... . 193
11.3.1 Experimental ............................... . 193
11.3.2 Supercritical Fluid Injection .................. . 194
11.3.3 High Pressure Liquid Injection ................ . 196
11.4 Supercritical Fluid Chromatography
and Supersonic Jet Spectroscopy .............. . 197
11.4.1 Experimental ............................... . 198
11.4.2 The Interfaces .............................. . 199
11.5 , Conclusions ................................ . 202
References ......................................... 202
Basic References Analytical Scale SFC/SFE ............ 203
Recommended Literature ............................ 207
Subject Index ...................................... 211