Explains why modern supercritical fluid chromatography (SFC) is the leading "green" analytical and purification separations technology.
Modern supercritical fluid chromatography (SFC) is the leading method used to analyze and purify chiral and achiral chemical compounds, many of which are pharmaceuticals, pharmaceutical candidates, and natural products including cannabis-related compounds. This book covers current SFC instrumentation as it relates to greater robustness, better reproducibility, and increased analytical sensitivity.
Modern Supercritical Fluid Chromatography: Carbon Dioxide Containing Mobile Phases covers the history, instrumentation, method development and applications of SFC. The authors provided readers with an overview of analytical and preparative SFC equipment, stationary phases, and mobile phase choices. Topics covered include: Milestones of Supercritical Fluid Chromatography; Physical Properties of Supercritical Fluids; Instrumentation for SFC; Detection in SFC; Achiral SFC Method Development; Chiral SFC Method Development; and Preparative Scale SFC. The book also includes highlights of modern applications of SFC in the final chapters - namely pharmaceuticals, consumer products, foods, polymers, petroleum-related mixtures, and cannabis - and discusses the future of SFC.
- Provides a clear explanation of the physical and chemical properties of supercritical fluids, which gives the reader a better understanding of the basis for improved performance in SFC compared to HPLC and GC
- Describes the advantages of SFC as a green alternative to HPLC and GC for the analysis of both polar, water-soluble, and non-polar analytes
- Details both achiral and chiral SFC method development, including modifiers, additives, the impact of temperature and pressure, and stationary phase choices
- Details why SFC is the premier modern preparative chromatographic technique used to purify components of mixtures for subsequent uses, both from performance and economic perspectives
- Covers numerous detectors, with an emphasis on SFC-MS, SFC-UV, and SFC-ELSD (evaporative light scattering detection)
- Describes the application of SFC to numerous high-value application areas
Modern Supercritical Fluid Chromatography: Carbon Dioxide Containing Mobile Phases will be of great interest to professionals, students, and professors involved in analytical, bioanalytical, separations science, medicinal, petroleum, and environmental chemistries. It will also appeal to pharmaceutical scientists, natural-product scientists, food and consumer-products scientists, chemical engineers, and managers in these areas.
Table of Contents
Preface xiii
1 Historical Development of SFC 1
1.1 Physical Properties of Supercritical Fluids 1
1.2 Discovery of Supercritical Fluids (1822-1892) 6
1.3 Supercritical Fluid Chromatography (1962-1980) 8
1.4 SFC with Open Tubular Columns (1980-1992) 15
1.5 Rediscovery of pcSFC (1992-2005) 19
1.6 Modern Packed Column SFC 22
References 24
2 Carbon Dioxide as the Mobile Phase 29
2.1 Introduction to Carbon Dioxide 29
2.2 Supercritical Carbon Dioxide 32
2.3 Solvating Power of Supercritical CO2 35
2.4 Solvating Power of Modified CO2 45
2.5 Clustering of CO2 49
References 52
3 Instrumentation for Analytical Scale Packed Column SFC 55
3.1 Introduction 56
3.2 Safety Considerations 56
3.3 Fluid Supply 58
3.3.1 Carbon Dioxide and Other Compressed Gases 58
3.3.2 Mobile Phase “Modifiers” and “Additives” 59
3.4 Fluid Delivery - Pumps and Pumping Considerations 60
3.4.1 Pump Thermostating 60
3.4.2 Fluid Pressurization and Metering 60
3.4.3 Modifier Fluid Pumping 61
3.4.4 Pressure and Flow Ranges 62
3.4.5 Fluid Mixing 62
3.5 Sample Injection and Autosamplers 62
3.6 Tubing and Connections 64
3.6.1 Tubing 64
3.6.1.1 Stainless Steel Tubing 64
3.6.1.2 Polymeric Tubing 65
3.6.2 Connections 66
3.7 Column and Mobile Phase Temperature Control 66
3.8 Chromatographic Column Materials of Construction 67
3.9 Backpressure Regulation 68
3.9.1 Passive Flow Restriction 69
3.9.2 Active Backpressure Regulation 70
3.10 Waste Disposal 72
3.11 Conclusion 72
References 72
4 Detection in Packed Column SFC 77
4.1 Introduction 78
4.2 Predecompression Detection (Condensed‐Fluid‐Phase Detection) 78
4.2.1 UV/VIS Absorbance 78
4.2.2 Fluorescence Detection 81
4.2.3 Electrochemical Detection 82
4.2.4 Other Less Common Condensed Phase Detectors 83
4.2.4.1 Flow‐Cell Fourier Transform Infra‐Red Absorbance (FTIR) Detection 83
4.2.4.2 Online Nuclear Magnetic Resonance (NMR) Detection 84
4.2.4.3 Refractive Index (RI) Detection 85
4.3 Postdecompression Detection (Gas/Droplet Phase Detection) - Interfacing Approaches 85
4.3.1 Pre-BPR Flow Splitting 86
4.3.2 Total Flow Introduction (Post-BPR Detection) 88
4.3.2.1 BPR Requirements for Total‐Flow Introduction Detection 88
4.3.2.2 Total Flow Introduction with Mechanical BPR 89
4.3.2.3 Total Flow Introduction - Pressure‐Regulating‐Fluid (PRF) Interface 89
4.3.2.4 Total Flow Introduction without Active Backpressure Regulation 91
4.4 Postdecompression Detection 93
4.4.1 Flame‐Based Detectors 93
4.4.2 Evaporative Light Scattering Detection (ELSD) and Charged Aerosol Detection (Corona CAD) 97
4.4.3 Mass Spectrometric Detection 98
4.4.3.1 Interfacing and Ionization Approaches 99
4.4.3.2 Atmospheric Pressure Chemical Ionization (APCI) 100
4.4.3.3 Pneumatically Assisted Electrospray Ionization (ESI) 101
4.4.3.4 Atmospheric Pressure Photoionization (APPI) 103
4.4.4 Postdecompression Detection Using Less Common Approaches - Deposition IR 103
4.5 Concluding Remarks 103
References 104
5 Chiral Analytical Scale SFC - Method Development, Stationary Phases, and Mobile Phases 117
5.1 Introduction 117
5.2 Chiral Stationary Phases for SFC 119
5.3 Chiral SFC vs. Chiral HPLC 128
5.4 Method Development Approaches 130
5.4.1 Modifiers for Chiral SFC 132
5.4.2 Additives for Chiral SFC 133
5.4.3 Nontraditional Modifiers 135
5.4.4 Method Development Approaches 137
5.5 High Throughput Method Development 139
5.6 Summary 141
References 142
6 Achiral Analytical Scale SFC - Method Development, Stationary Phases, and Mobile Phases 147
6.1 Introduction 147
6.2 The Mixture to Be Separated 148
6.2.1 Molecular Interactions 148
6.2.2 Molecular “Handles” 149
6.3 Achiral SFC Stationary Phases 150
6.3.1 Column Safety and Compatibility 150
6.3.2 Efficiency 150
6.3.3 Retention 153
6.3.4 Selectivity 156
6.4 Mobile‐Phase Choices 157
6.4.1 Primary Mobile‐Phase Component 158
6.4.2 Secondary Mobile‐Phase Component - The “Modifier” 159
6.4.3 Tertiary Mobile‐Phase Component - “Additives” 163
6.5 Influence of Column Temperature on Efficiency and Selectivity 170
6.6 Where Do I Go from Here? Method Development Decision Tree and Summary 172
References 174
7 Instrumentation for Preparative Scale Packed Column SFC 183
7.1 Introduction 183
7.2 Safety Considerations 184
7.3 Fluid Supply 185
7.3.1 Carbon Dioxide 185
7.3.2 Mobile Phase Modifiers and Additives 187
7.3.3 Carbon Dioxide Recycling 188
7.4 Pumps and Pumping Considerations 189
7.4.1 CO2 and Modifier Fluid Pumping 189
7.4.2 Pressures and Flow Ranges 189
7.5 Sample Injection 190
7.5.1 Injection of Solutions 190
7.5.2 Extraction Type Injection 190
7.6 Chromatographic Columns 192
7.7 Detection 192
7.8 Back Pressure Regulation 193
7.9 Fraction Collection 193
7.9.1 Cyclone Collection 194
7.9.2 Open‐Bed Collection 195
7.10 Conclusion 197
References 197
8 Preparative Achiral and Chiral SFC - Method Development, Stationary Phases, and Mobile Phases 199
8.1 Introduction 200
8.1.1 Advantages and Disadvantages of SFC vs. HPLC for Purification 201
8.1.2 Cost Comparison: Preparative HPLC vs. SFC 202
8.2 Safety Considerations 202
8.3 Developing Preparative Separations 203
8.3.1 Linear Scale‐Up Calculations 209
8.3.2 Scaling Rule in Supercritical Fluid Chromatography 210
8.3.3 Metrics for Preparative Separations 213
8.3.4 Options for Increasing Purification Productivity 214
8.3.4.1 Closed‐Loop Recycling 214
8.3.4.2 Stacked Injections 214
8.3.5 Importance of Solubility on Preparative Separations 214
8.3.6 Preparative SFC Injection Options 217
8.4 Preparative Chiral SFC Purifications 220
8.4.1 Chiral Stationary Phases (CSPs) for Preparative SFC 220
8.4.2 Method Development for Chiral Purifications 222
8.4.3 Preparative SFC Examples 223
8.4.3.1 Milligram Scale Chiral Purification 223
8.4.3.2 Gram Scale Chiral Purification 224
8.4.4 Impact of Solubility on Productivity 226
8.4.5 Use of Immobilized Chiral Stationary Phase (CCP) for Solubility‐Challenged Samples 227
8.4.5.1 Immobilized CSP Example #1 227
8.4.5.2 Immobilized CSP Example #2 228
8.4.6 Coupling of Chiral and Achiral Columns for SFC Purifications 229
8.5 Preparative Achiral SFC Purifications 231
8.5.1 Introduction to Achiral SFC Purifications 231
8.5.2 Stationary Phases for Achiral Preparative SFC 232
8.5.3 Method Development for Achiral Purifications 232
8.5.4 Achiral SFC Purification Examples 234
8.5.4.1 Achiral Purification Example #1 234
8.5.4.2 Achiral Purification Example #2 234
8.5.5 Purifications Using Mass‐Directed SFC 236
8.5.6 Impurity Isolation Using Preparative SFC 237
8.5.6.1 Impurity Isolation Example 240
8.5.7 SFC as Alternative to Flash Purification 241
8.6 Best Practices for Successful SFC Purifications 244
8.6.1 Sample Filtration and Inlet Filters 244
8.6.2 Sample Purity 246
8.6.3 Salt vs. Free Base 247
8.6.4 Primary Amine Protection to Improve Enantiomer Resolution 250
8.6.5 Evaluation of Alternate Synthetic Intermediates to Improve SFC Purification Productivity 250
8.7 Summary 254
References 254
9 Impact and Promise of SFC in the Pharmaceutical Industry 267
9.1 Introduction to Pharmaceutical Industry 267
9.2 SFC in Pharmaceutical Discovery 268
9.2.1 Early Discovery Support 268
9.2.2 SFC in Medicinal Chemistry 269
9.2.2.1 Analytical SFC 270
9.2.2.2 Preparative SFC 271
9.2.3 Physiochemical Measurement by SFC 273
9.2.4 Use of SFC for Pharmacokinetic and Drug Metabolism Studies 274
9.3 SFC in Development and Manufacturing 276
9.3.1 Analytical SFC Analysis of Drug Substances and Drug Products 276
9.3.2 Preparative SFC in Development and Manufacturing 282
9.3.3 Metabolite/PKDM Studies in Development 283
9.3.4 SFC in Chemical Process Development 283
9.4 SFC for Analysis of Illegal Drugs 284
9.5 Summary 286
References 286
10 Impact of SFC in the Petroleum Industry 297
10.1 Petroleum Chemistry 297
10.1.1 Crude Refining Processes 297
10.1.2 Petrochemical Processes 298
10.2 Introduction to Petroleum Analysis 299
10.3 Historical Perspective 301
10.3.1 Hydrocarbon Analysis via FIA 301
10.3.2 SFC Replaces FIA 301
10.3.3 Hydrocarbon SFC Analysis via ASTM 5186‐91 302
10.4 Early Petroleum Applications of SFC 304
10.4.1 Samples with Broad Polymer Distribution 304
10.4.2 SFC Purification of Polycyclic Aromatic Hydrocarbons 305
10.4.3 Coal Tar Pitch 305
10.4.4 Enhanced SFC Performance 305
10.4.5 Sulfur Detection in a Petroleum Matrix 307
10.5 SFC Replacement for GC and LC 308
10.5.1 Simulated Distillation 308
10.5.2 Hydrocarbon Group‐Type Separations - PIONA Analysis 310
10.6 Biodiesel Purification 311
10.7 Multidimensional Separations 314
10.7.1 Comprehensive Two‐Dimensional SFC 314
10.7.2 SFC‐GC × GC 315
10.7.3 Comprehensive - SFC‐Twin‐Two‐Dimensional (GC × GC) 316
References 317
11 Selected SFC Applications in the Food, Polymer, and Personal Care Industries 321
11.1 Introduction 321
11.2 Selected Applications in the Foods Industry 322
11.2.1 Fats, Oils, and Fatty Acids 322
11.2.2 Tocopherols 325
11.2.3 Other Vitamins 327
11.2.4 Food Preservatives (Other Antioxidants and Antimicrobials) 330
11.2.5 Coloring Agents 330
11.2.6 Sugars 331
11.3 Selected Applications in the Field of Synthetic Polymers 332
11.3.1 Molecular Weight Distribution 332
11.3.2 Structural Characterization 334
11.3.3 “Critical Condition” Group/Block Separations of Complex Polymers Using CO2‐containing Mobile Phases 334
11.3.4 Polymer Additives 335
11.4 Selected Applications in the Personal Care Industry 337
11.4.1 Lipophilic Components of Cosmetics 337
11.4.2 Surfactants in Cleaning Mixtures 337
11.4.3 Emulsifiers in Personal Care Products 337
11.4.4 Preservatives 338
11.5 Conclusions 340
References 340
12 Analysis of Cannabis Products by Supercritical Fluid Chromatography 347
12.1 Introduction 347
12.1.1 Cannabis History 348
12.2 Analytical SFC 351
12.2.1 Introduction 351
12.2.2 Early SFC of Cannabis Products 352
12.2.3 Achiral SFC 353
12.2.4 Chiral SFC 354
12.2.5 Metabolite Analysis 357
12.3 Preparative SFC 357
12.4 Summary 360
References 361
13 The Future of SFC 365
13.1 Introduction 365
13.2 SFC Publication Record 366
13.3 SFC Research in Academia 368
13.4 SFC Conferences 368
13.5 Anticipated Technical Advances 369
13.6 Limits to SFC Expansion 370
13.7 Summary 372
References 373
Index 377
