Huethig Verlag 1987. 591 Seiten; gebundene Ausgabe

Sprache: Englisch

ISBN: 3778515519
EAN: 9783778515518

Bestell-Nr: 1122498

Bemerkungen: Das hier angebotene Buch stammt aus einer teilaufgelösten wissenschaftlichen Bibliothek und trägt die entsprechenden Kennzeichnungen (Rückenschild, Instituts-Stempel...). Schnitt und Einband sind etwas staubschmutzig; Buchschnitt und Seitenränder alters-/papierbedingt angebräunt; Der Buchzustand ist ansonsten ordentlich und dem Alter entsprechend gut. Contents A On-Column Injection 1 Introduction 1 1.1 Definition 1 1.2 Historical Background 1 1.3 Topics Considered in this Part 7 2 Introduction of the Sample 10 2.1 Injection Speed 10 2.1.1 Why is Slow Injection Attractive? 10 2.1.2 Separation from the Sampling Device .. 11 2.1.3 Sample Evaporation on the Syringe Needle 14 2.2 Accuracy of the Injected Sample Volume 17 2.3 Minimal Sample Volume 21 2.3.1 Problems Caused by Too Small Sample Volumes 21 2.3.2 Mechanical Transfer of Small Sample Volumes 22 2.3.3 Some Experimental Results 23 2.3.4 Conclusions 25 2.4 Returning Sample Plug 25 2.4.1 Carrier Gas Acting as Spring 25 2.4.2 Factors Contributing to a Return of the Sample Plug : 26 2.4.3 Experimentally Determined Conditions Causing Return of Sample Plug 28 2.4.4 Effects Caused by the Return of the Sam­ ple Plug to the Needle 29 2.4.5 Conclusions 35 2.5 Column Temperature During Injection .. 36 2.5.1 Effects of Column Temperature on On- Column Injection 36 2.5.2 Vapor Pressure of the Sample 40 http://d-nb.info/8709173072.5.3 Recommended Maximum Injection Temperatures 44 2.5.4 Cooling of Injector and Column 45 2.5.5 Temperature Increase after Injection ... 46 3 Injector Design 48 3.1 Column and Needle Alignment 48 3.2 Remarks on the Introduction of the Sy­ ringe Needle 50 3.3 Minimization of Effects Caused by Return of Sample Plug 51 3.3.1 Length of the Cool Inlet Section in the Injector 51 3.3.2 Bridge Effect Pulling Sample Liquid out of the Column 51 3.4 Valve Systems 55 3.4.1 Rotating Valves 55 3.4.2 Plastic Seals 60 3.4.3 Backflow Due to Pressure Drop 62 3.4.4 Tightness of On-Column Injectors 65 3.5 Pressure-Regulated Carrier Gas Supply . 66 3.5.1 Advantages of Pressure Regulation 66 3.5.2 Requirements Regarding Pressure Regulators 66 3.5.3 Injector Purge Helping to Stabilize Inlet Pressure 69 3.5.4 Safety Aspects on Using Hydrogen as Carrier Gas 70 3.6 Flow-Regulated Carrier Gas Supply 71 3.6.1 Flow Regulation and Separation Efficiency 72 3.6.2 Elution Temperatures 74 3.6.3 Regulation of Meaningful Units 75 3.6.4 Safety in Using Hydrogen as Carrier Gas 75 3.6.5 Exclusion of Sample Backflow? 75 3.6.6 Evaporation of Large Solvent Volumes . 76 3.6.7 Tightness of Injectors 76 3.7 Injector Contamination 76 3.7.1 "Ghost" Peaks after Cold Trapping 77 3.7.2 Typical Symptoms of Injector Con­ tamination 77 3.7.3 Sources of Injector Contamination 78 3.7.4 Permanent Injector Purge 79 3.7.5 Cleaning of On-Column Injectors 80 3.8 Cooling of On-Column Injectors 81 3.9 In-House Fabricated On-Column Injectors 83 3.9.1 Designs Based on Vaporizing Injectors . 84 3.9.2 Injectors for Wide-Bore Columns (Pre- Columns) 86 3.9.3 Fixed Needle Injector 87 3.9.4 T-Piece Added to Vaporizing Injector... 88 3.10 On-Column Injectors of Differing Concepts 90 3.10.1 Rotary Valve On-Column Injector 90 3.10.2 On-Column Split Injection 93 3.10.3 On-Column Injection onto 0.1 mm i.d. Capillaries 97 3.10.4 At-Column Injection 98 3.10.5 "Closed" On-Column Injector 99 4 On-Column Syringes 101 4.1 Needle Diameters 101 4.1.1 Internal Needle Diameter 101 4.2 Length of Syringe Needle 103 4.3 Syringes with Fixed Steel Needles 103 4.4 Syringes with Removable Fused Silica Needles 105 4.5 Sheathed Needles 106 4.6 Cleaning the Interior of On-Column Syringes 107 4.7 Cleaning of the Outer Needle Wall 108 5 Band Broadening in Space 110 5.1 Introduction 110 5.2 The Flooding Sample 112 5.2.1 Primary and Secondary Flow of Liquid . 113 5.2.2 Expansion by Evaporation and Recon- densation 114 5.3 Solvent Evaporation 115 5.3.1 Low Column Temperature: Evaporation from Rear to Front 115 5.3.2 Evaporation from the Front at High Col­ umn Temperatures 115 5.3.3 Effect on High Boiling Solutes 116 5.3.4 Effect on Volatile Solutes 116 5.4 Length of the Flooded Zone 118 5.4.1 Importance of this Parameter 118 5.4.2 Determination of the Length of the Flooded Zone 118 5.4.3 Factors Influencing Length of Flooded Zone 120 5.4.4 Lengths of the Flooded Zones in Coated Columns 125 5.5 Peak Broadening Due to Band Broaden­ ing in Space 127 5.5.1 A Model Case 127 5.5.2 Some Realistic Cases 129 5.6 Peak Distortion 134 5.7 Summarized Symptoms of Band Broadening in Space 139 5.8 Avoidance of Peak Distortion by Band Broadening in Space 139 5.8.1 An Observed Phenomenon 140 5.8.2 Explanation of the Effect 143 5.8.3 Temporary Cooling of the Column Inlet. 148 5.8.4 Solvent Effects 149 5.9 High Injection Temperature or Retention Gap? 150 6 Solvent Effects 152 6.1 Importance of Solvent Effects 153 6.2 Solvent Evaporation below Solvent Boil­ ing Point 154 6.3 Solvent Evaporation above Solvent Boil­ ing Point 155 6.3.1 Failing Solvent Trapping 156 6.3.2 Role of Phase Soaking 156 7 Involatile Sample By-Products 159 7.1 Introduction 159 7.2 Deposition of Involatile Sample By- Products 160 7.3 Effects of Involatile Sample By-Products 162 7.3.1 Peak Distortion 162 7.3.2 Column Bleeding 162 7.3.3 Film Disruption 163 7.3.4 Adsorption Effects 166 7.3.5 Solute Degradation 167 7.3.6 Phase Stripping 168 7.4 Dirt Exhibiting Retention Power 168 7.4.1 Inhomogeneous Dirt Distribution 169 7.4.2 Dependence on Injection 169 7.4.3 Effect on Quantitative Analysis 171 7.4.4 Accentuated Band Broadening in Space 173 7.4.5 Uncoated Column Inlets (Retention Gaps) 177 7.5 Conclusions 179 7.5.1 Use of Retention Gaps 179 7.5.2 Disposable Column Inlet 180 7.5.3 Thick Film Columns 182 8 High Oven Temperature On-Column Injection 183 8.1 Introduction 183 8.2 Two Concepts 185 8.2.1 Sample Coating Cooled Inlet 186 8.2.2 Barrier to Backflow 186 8.3 Required Length of the Cooled Inlet ... 187 8.3.1 Sample Coating Cooled Inlet 187 8.3.2 Barrier to Backflow 187 8.3.3 Conclusion 190 8.4 On-Column Injectors Temporarily Cooling the Column Inlet 190 8.4.1 Secondary Cooling 190 8.4.2 Extended Secondary Cooling 196 8.4.3 Movable On-Column Injector 199 8.4.4 Independently Thermostated Column Inlet 202 8.5 When to Heat the Column Inlet 203 8.5.1 Original Recommendations 203 8.5.2 Temporary Cooling for Conventional On- Column Injection 203 8.5.3 High Oven Temperature On-Column Injection 204 8.5.4 Determination of the Solvent Evaporation Time 205 8.6 Initial Band Shapes 205 8.6.1 Sample Coating Cooled Inlet 206 8.6.2 Barrier to Backflow 210 8.6.3 Coated Column Inlets or Retention Gaps? 215 8.7 Quantitative Analysis 218 8.7.1 Undetected, Prematurely Released Material 218 8.7.2 Returning Sample Liquid 219 8.8 Summarized Working Rules 223 8.8.1 Sample Coating Cooled Inlet 223 8.8.2 Barrier to Backflow 224 8.9 Evaluation of High Oven Temperature On- Column Injection 225 8.9.1 Rapid Isothermal Analysis 225 8.9.2 Comparison of Injectors 226 9 Simplified Guidelines on On-Column Injection 228 9.1 Conventional On-Column Injection 228 9.2 High Oven Temperature On-Column In­ jection 230 10 Evaluation of On-Column Injection 230 10.1 Accuracy and Reliability of Quantitative Results 230 10.2 Simplicity of Quantitation 232 10.3 No Degradation of Labile Solutes 233 10.4 Flexibility of Sample Volume 233 10.5 Not a Universal Injector 233 10.5.1 Necessity of Dilution 234 10.5.2 Solvent Effects 236 10.5.3 Dirty Samples 236 10.5.4 Headspace Analysis 237 B Solvent Effects 1 Introduction 245 1.1 Definitions 245 1.1.1 Band Broadening in Space 246 1.1.2 Solvent Trapping 247 1.1.3 Phase Soaking 247 1.2 Historic Development 247 1.2.1 Solvent Effects in Packed Column GC . 247 1.2.2 Solvent Effects in Splltless Injection ... 249 1.2.3 Solvent Trapping 251 1.2.4 Phase Soaking 253 1.2.5 Theory 254 1.3 Aims of this Part 255 2 Solvent Trapping 255 2.1 Direction of Solvent Evaporation 256 2.2 Distribution of the Solutes in the Sample Layer 257 2.2.1 Distribution Due to the Flow of Sample Liquid 257 2.2.2 Recondensation of Solvent ahead of the Sample Layer? 258 2.3 Partial Vapor Pressure 259 2.3.1 Alkanes in an Alkane as an Example .. 260 2.3.2 Alkanes in 1-Pentanol 261 2.4 Forms of Solvent Trapping 263 2.4.1 Non-Trapping 263 2.4.2 Partial Solvent Trapping 264 2.4.3 Full Trapping 267 2.5 Effects on Retention Times 270 2.6 Some Examples 271 3 Phase Soaking 278 3.1 Principles 278 3.1.1 Overloaded Stationary Phase 278 3.1.2 Shape of the Solvent Band 279 3.1.3 Velocity of the Solvent Band 281 3.2 Reconcentration of Solute Bands Eluted after the Solvent Peak 283 3.2.1 An Experimentally Investigated Reconcentration Effect 283 3.2.2 Mechanism of Reconcentration 285 3.2.3 Range of Effectiveness 289 3.3 Retardation Factors 293 3.3.1 Soaking Intensity 293 3.3.2 Importance of Retardation Factors 294 3.3.3 Experimentally Determined Retardation Factors 295 3.3.4 Examples 299 3.3.5 Final Remarks 301 3.4 Effects on Retention Times 302 3.4.1 Gradual Changes of Retention Times .. 302 3.4.2 Changes in Selectivity 305 3.5 Effect on Separation Efficiency 305 3.6 Phase Soaking and Large Sample Volumes 306 3.6.1 Reduced Peak Areas 306 4 Techniques for Avoiding Peak Broaden­ ing by Partial Solvent Trapping 310 4.1 Introduction 310 4.2 Improved Solvent Trapping 313 4.2.1 Full Trapping 313 4.2.2 Non-Trapping 315 4.3 Reconcentration of Partially Trapped Solutes by Phase Soaking 316 4.3.1 Principle 316 4.3.2 Occurrence 316 4.3.3 The Case of Chloroform as an Example 318 4.3.4 Some General Guidelines 322 4.4 Co-Injection 323 4.4.1 Concepts 323 4.4.2 Mixing of Sample and Solvent 324 4.4.3 Addition of a Different Solvent 326 4.4.4 Evaporation Times of the Solvents 327 4.4.5 General Evaluation of Co-Injection Techniques 330 4.5 Makeshifts for Reducing Peak Broadening 330 4.5.1 Purpose of Makeshifts 330 4.5.2 Minimized Solvent Evaporation Time ... 330 4.5.3 Column of High Retention Poij/er 333 5 Solvent Effects on Peaks Eluted Before the Solvent 334 5.1 Problem of Peak Distortion 334 5.1.1 Samples Dissolved in a Solvent 334 5.1.2 The "Big Peak" Problem 335 5.2 Solvent Trapping Effects 338 5.2.1 Forms of Trapping of Solutes Eluted Before the Solvent 338 5.2.2 Need for Non-Trapping 339 5.3 Phase Soaking Effects 340 5.3.1 Effects before and after the Solvent Peak 340 5.3.2 Effectiveness Depending on Solvent Trapping 340 5.3.3 Weakness of the Broadening Effect.... 340 5.3.4 Static Broadening Effect 342 5.3.5 Dynamic Broadening Effect 342 5.4 Examples 343 5.5 Conclusions 346 6 Summarized Symptoms of Peak Distor­ tion Due to Solvent Effects 347 7 Closing Remark: Importance of Solvent Effects for Future Developments 349 8 References Part B 353 C Retention Gap Techniques 1 introduction 357 1.1 Definition 357 1.2 Historical Background 357 2 Purposes of Using Uncoated Column Inlets 359 2.1 Disposable Inlet for Dirty Samples 360 2.2 Avoidance of Peak Distortion on Injection of Conventional Sample Volumes 361 2.2.1 Splitless Injection 361 2.2.2 On-Column Injection 362 2.3 Injection of Large Sample Volumes .... 362 2.3.1 Increased Sensitivity for the Analysis of Volatile Solutes 363 2.3.2 Introduction of the Complete Sample .. 364 2.3.3 Convenience of Sample Preparation ... 364 2.4 Automated On-Column Injection 365 2.5 Narrow Bore Separation Columns 366 2.6 On-Line Coupled HPLC-GC 368 3 Mechanism of Solute Reconcentration Using Retention Gaps 368 3.1 Two-Step Chromatography 369 3.2 Phase Ratio Focusing 371 3.3 Column-Internal Cold Trapping 375 3.3.1 Nature of Cold Trapping 376 3.3.2 An Experimental Result 382 3.3.3 Conclusions for Practical Work 385 4 Required Length of the Retention Gap . 391 4.1 Sample Liquid Must Not Enter the Separation Column 391 4.2 Length of the Flooded Zone 393 4.2.1 Checking Length of Flooded Zone 394 4.2.2 Wettability 394 4.2.3 Roughened Internal Surfaces? 396 4.2.4 Minimal Velocity of the Sample Plug ... 397 4.2.5 Lengths of the Flooded Zones at Low Temperatures 398 4.2.6 Lengths of the Flooded Zones at Elevated Temperatures 398 4.3 The Etzweiler Bulb 400 5 Reconcentration Power Using Retention Gaps 403 5.1 Difference in Retention Powers 403 5.2 Retention Power in the Retention Gap . 404 5.2.1 Retention Power Expressed as "Apparent Film Thickness" 404 5.2.2 Determination of Retention Powers in Retention Gaps 404 5.2.3 Deteriorated Retention Gaps 409 5.2.4 Experimental Determined Retention Powers 410 5.2.5 How Rapidly Are Retention Gaps "Filled In"? 413 5.3 Minimum Film Thickness in Separation Columns 415 5.3.1 Adjustment of Reconcentration Power by Separation Column 415 5.3.2 Maximum Tolerable Residual Band Length 415 5.3.3 Mathematical Formula for Calculating Minimal Film Thickness 417 5.3.4 Calculated Examples 419 5.3.5 Stepwise Estimation 421 5.3.6 Two Experimental Results . 424 5.4 Band Broadening Due to Longitudinal Diffusion 427 5.4.1 Conditions Required for Peak Broadening 427 5.4.2 Extent of Peak Broadening 428 5.4.3 Conclusions 430 6 Preparation of Retention Gaps 432 6.1 Extraction of the Stationary Phase 432 6.2 Producing Partially Coated Columns ... 435 6.3 Deactivation of Pre-Columns 436 6.3.1 Advantages of Using Pre-Columns 436 6.3.2 Commercial or Home-Made Pre- Columns? 437 6.3.3 Deactivation by Silylation 438 6.3.4 Deactivation with Carbowax 440 7 Connections between Capillaries 441 7.1 Critical Points 442 7.1.1 Tightness of Capillary Connections .... 442 7.1.2 Hydrogen in the GC Oven 442 7.1.3 Distortion of Solvent Peak 443 7.1.4 Losses of Solute Material 445 7.1.5 Dead Volumes 448 7.2 Shrinkable PTFE Connections 449 7.2.1 Preparation of the Connection 449 7.2.2 Thermostability of PTFE Connections .. 450 7.2.3 Possibility of Repeated Use 451 7.2.4 Gas Tightness of PTFE Connections ... 453 7.2.5 Chromatographic Behavior of PTFE Connections 456 7.3 Butt Connectors 458 7.3.1 Historic Remarks 458 7.3.2 One-Ferrule Connectors 459 7.3.3 Two-Ferrule Connectors 462 7.3.4 Purged Connectors 465 7.3.5 Ferrule Materials 467 7.3.6 Some Important Manipulations 469 7.3.7 Thermal Mass of Connectors 473 7.4 Glued Connections 474 7.4.1 Alignment and Mechanical Stabilization 474 7.4.2 Polyimide Glue 478 7.4.3 Silicone Glue 480 7.4.4 Silver Chloride 483 7.4.5 Evaluation of Glued Connections 483 7.5 Fused Connections 486 7.5.1 Thermal Expansion of Glasses and Fused Silica 485 7.5.2 Materials and Methods 486 7.5.3 Connections between Two Fused Silica Capillaries 491 7.5.4 Connections between Glass and Fused Silica Capillaries 494 7.5.5 Joints between Glass Capillaries 500 7.5.6 Evaluation of Fused Connections 503 7.6 Press-Fit Connections 503 7.6.1 Making Connections 503 7.6.2 Tightness, Mechanical Strength 504 7.6.3 Gas Chromatographic Inertness 505 7.6.4 Preparation of Connection Tubes 506 7.6.5 Press-Fit Connections between Glass and Fused Silica Capillaries 508 8 On-Column Injection of Large Sample Volumes 512 8.1 Concept 512 8.1.1 Problems of Broad Initial Bands 512 8.1.2 Reconcentration of Solute Bands 513 8.2 Isothermal Analysis at Injection Tempera­ ture 516 8.2.1 Phase Stripping 516 8.2.2 Length of the Column 517 8.2.3 Effects on Retention Times 517 8.3 System Suitable for Analyses Involving Temperature Increase 520 8.3.1 Wettability of Uncoated Column Inlet .. 521 8.3.2 Length of Uncoated Inlet 521 8.3.3 Film Thickness in Separation Column .. 522 8.3.4 Contamination of Uncoated Inlets 524 8.3.5 Coupling Pre-Columns to Separation Columns 527 8.4 Chromatographic Conditions 528 8.4.1 Carrier Gas Flow Rate 528 8.4.2 Injection Temperature 532 8.4.3 Solvent Evaporation Temperature 533 8.4.4 Flow-Regulated Carrier Gas? 535 8.4.5 Speed of Temperature Increase 537 8.5 Injection 539 8.5.1 Sample Solvent 539 8.5.2 On-Column Syringes for Large Volumes 540 8.5.3 Injection Speed 540 8.6 Large Amounts of Solvent and Detectors 545 8.6.1 Possible Problems with Detectors 545 8.6.2 Switching Off the Detector 546 8.6.3 Required Air Flow Rate for Complete Combustion 547 8.6.4 Solvent By-Passing 548 8.7 Summarized Guidelines 556 9 Automated On-Column Injection 557 9.1 Modes of Automatic On-Column Injection 558 9.2 Special Characteristics of Wide Bore Retention Gaps 559 9.2.1 Length of the Flooded Zone 559 9.2.2 Residual Initial Band Widths 560 9.2.3 Gas Velocities in Pre-Columns 561 9.2.4 Limits to the Size of Pre-Columns 562 9.2.5 Connections between Pre-Column and Separation Column 563 9.3 Injection of Small Sample Volumes 563 9.3.1 Purge System 563 9.3.2 Injector Valves 565 9.3.3 Reproducibility of Peak Areas 565 9.3.4 Summarizing Guidelines 566 9.4 Injection of Large Sample Volumes .... 567 9.4.1 Injection Speed 567 9.4.2 Principle of Sample Introduction 567 9.4.3 Injection Volumes 568 9.4.4 Some Results 570 9.4.5 Summarizing Guidelines 571 10 References Part C 574 Appendix I — Troubleshooting 578 Appendix II — Glossary 581 Subject Index 585

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