Troubleshooting and maintenance guide for gas chromatographers

✍ Scribed by Dean Rood

• Year: 2007
• Tongue: English
• Leaves: 346
• Edition: 4th, Revised and Updated Edition
• Category: Library

✦ Synopsis

This fourth edition of the classic guide for every user of gas chromatographic instrumentation is now updated to include such new topics as fast GC using narrow, short columns, electronic pressure control, and basic aspects of quantitative gas chromatography.The author shares his many years of experience in technical support for gas chromatography users, addressing the most common problems, questions and misconceptions in capillary gas chromatography. He structures and presents the material in a concise and practical manner, suitable even for the most inexperienced user without any detailed knowledge of chemistry or chromatography.For lab technicians in chemistry, analytical, food, medicinal and environmental chemists, pharmaceutists.

✦ Table of Contents

Cover page......Page 1
The Troubleshootingand Maintenance Guidefor Gas Chromatographers......Page 4
Preface......Page 6
Contents......Page 8
Intentions and Introduction......Page 20
1.2
What Types of Compounds Are Suitable for GC Analysis?......Page 22
1.3.1
Gas Supply and Flow Controllers......Page 23
1.3.3
Capillary Column and Oven......Page 24
1.4 The Chromatogram......Page 25
1.5.1
A Simple Description of the Chromatographic Process......Page 27
1.5.2
A Detailed Description of the Chromatographic Process......Page 28
1.6.1
Stationary Phase......Page 30
1.6.3
Column Temperature......Page 31
2.2.2
Peak Symmetry......Page 33
2.3.3 Retention Factor......Page 35
2.3.4 Retention Index
......Page 37
2.4 Phase Ratio......Page 38
2.5 Distribution Constant......Page 39
2.6Column Effi ciency......Page 40
2.6.2
Height Equivalent to a Theoretical Plate......Page 41
2.6.4
Precautions When Using Theoretical Plates......Page 42
2.7
Utilization of Theoretical Effi ciency......Page 43
2.9
Resolution......Page 44
2.10
Trennzahl......Page 46
2.11
Column Capacity......Page 47
3.2
Fused Silica Tubing......Page 49
3.4
Other Tubing Materials......Page 51
3.5
Polyimide Fused Silica Tubing Bending Stress......Page 52
4.1
Stationary Phases......Page 53
4.2.1
Polysiloxanes or Silicones......Page 54
4.2.3
Polyethylene Glycols......Page 56
4.2.4
Porous Layer Stationary Phases......Page 57
4.3.2
Stationary Phase Polarity......Page 58
4.3.3
Stationary Phase Selectivity......Page 59
4.4.1
Dispersion Interaction......Page 60
4.4.2
Dipole Interaction......Page 61
4.4.3
Hydrogen Bonding Interaction......Page 62
4.4.4
When There are Multiple Interactions......Page 63
4.5
Stationary Phase Equivalencies......Page 64
4.6
Column Temperature Limits......Page 65
4.7.1
What is Column Bleed?......Page 66
4.7.2
Measuring Column Bleed......Page 67
4.7.4
Detector Considerations......Page 68
4.8
Selecting Stationary Phases......Page 69
5.2.1
Column Length and Effi ciency/Resolution......Page 72
5.2.3
Column Length and Pressure......Page 76
5.2.6
Selecting Column Length......Page 77
5.3.1
Column Diameter and Effi ciency/Resolution......Page 78
5.3.3 Column Diameter and Pressure......Page 81
5.3.5 Column Diameter and Capacity......Page 82
5.3.7 Column Diameter and Injector Effi ciency......Page 83
5.3.10 Selecting Column Diameter......Page 84
5.4.1 Column Film Thickness and Retention......Page 85
5.4.2 Column Film Thickness and Effi ciency/Resolution......Page 88
5.4.3 Column Film Thickness and Capacity......Page 89
5.4.5 Column Film Thickness and Inertness......Page 90
5.5 Manipulating Multiple Column Dimensions......Page 91
6.3
Controlling the Linear Velocity and Flow Rate......Page 93
6.4
Van Deemter Curves......Page 94
6.5.1
Average Linear Velocity......Page 95
6.5.2Column Flow Rate......Page 98
6.6.2
Helium......Page 99
6.6.3
Hydrogen......Page 101
6.7
Recommended Average Linear Velocities......Page 102
6.8
Gas Purities......Page 105
6.9
Common Carrier Gas Problems......Page 106
7.2
The Basics of Vaporization Injectors......Page 108
7.2.3
Injector Backfl ash......Page 110
7.2.4
Injector Discrimination......Page 113
7.3.1
Description of a Split Injector......Page 114
7.3.2
Split Ratio......Page 115
7.3.4
Split Injector Liners......Page 118
7.3.5
Column Position in Split Injectors......Page 120
7.4.1
Description of a Splitless Injector......Page 121
7.4.2 Selecting Purge Activation Times......Page 124
7.4.3Solvent Effect for Splitless Injectors......Page 125
7.4.5 Septum Purge for Splitless Injectors......Page 127
7.4.7 Column Position in Splitless Injectors......Page 128
7.4.8 Other Aspects of Splitless Injectors......Page 129
7.4.9 Common Problems with Splitless Injectors......Page 130
7.5.1 Description of a Direct Injector......Page 131
7.5.2 Direct Injection Liners......Page 132
7.5.5 Other Aspects of Direct Injectors......Page 134
7.5.6 Common Problems with Direct Injectors......Page 135
7.6.1 Description of an On-Column Injector......Page 136
7.6.2 Solvent Effect and Cold Trapping for Cool On-Column Injectors......Page 137
7.6.4 Retention Gaps and Cool On-Column Injectors......Page 138
7.6.6 Common Problems With On-Column Injectors......Page 139
7.7.1 Description of Programmable Injectors......Page 140
7.7.3 Constant Flow or Velocity Mode......Page 141
7.7.4 Pressure Program Mode......Page 142
7.7.5 Pulsed Pressure Mode......Page 143
7.7.7 Other Aspects of Programmable Injectors......Page 144
7.8.1 Syringe Filling Techniques......Page 145
7.8.2 Injection Speed......Page 147
7.9 Autosamplers......Page 148
7.10.3 Septa Bleed......Page 150
7.10.4 Handling Septa......Page 152
7.11.1 Cleaning Injectors......Page 153
7.11.3 Cleaning Injector Liners......Page 154
7.11.4 Silylating Injector Liners......Page 155
8.2.1 Detector Dead Volume......Page 158
8.2.2 Detector Makeup or Auxiliary Gas......Page 159
8.2.3 Detector Temperature......Page 160
8.2.4 Detector Sensitivity......Page 161
8.2.5 Detector Selectivity......Page 162
8.2.6 Detector Linear Range......Page 163
8.3.1 FID Principle of Operation......Page 164
8.3.2 FID Gases......Page 165
8.3.6 FID Sensitivity and Linear Range......Page 166
8.3.8 FID Maintenance......Page 167
8.3.9.2 Diffi culty in Lighting the FID Flame......Page 168
8.3.9.4 Miscellaneous Problems with a FID......Page 169
8.4.1 NPD Principle of Operation......Page 170
8.4.3 Column Position in a NPD......Page 171
8.4.6 NPD Sensitivity and Linear Range......Page 172
8.4.7 NPD Maintenance......Page 173
8.4.8.2 Peak Shape Problems Attributed to the NPD......Page 174
8.4.8.3 NPD Baseline Problems......Page 175
8.5.1 ECD Principle of Operation......Page 176
8.5.3 Column Position in an ECD......Page 177
8.5.5 ECD Selectivity......Page 178
8.5.7 ECD Maintenance......Page 179
8.5.8.1 Change in ECD Sensitivity......Page 180
8.5.8.3 ECD Baseline Problems......Page 181
8.5.8.6 Miscellaneous Problems with an ECD......Page 182
8.6.1 TCD Principle of Operation......Page 183
8.6.2 TCD Gases......Page 184
8.6.6 TCD Sensitivity and Linear Range......Page 185
8.6.7 TCD Maintenance......Page 186
8.6.8.1 Change in TCD Sensitivity......Page 187
8.6.8.3 TCD Baseline Problems......Page 188
8.7.1 FPD Principle of Operation......Page 189
8.7.2 FPD Gases......Page 190
8.7.6 FPD Sensitivity and Linear Range......Page 191
8.7.8 FPD Maintenance......Page 192
8.7.9.4 FPD Flame Frequently Goes Out......Page 193
8.8.1 MS Principle of Operation......Page 194
8.8.2 Mass Spectral Data......Page 196
8.8.3 Other Ionization, Detection and Mass Filtering Modes......Page 197
8.8.5 MS Sensitivity and Linear Range......Page 198
8.8.6 MS Temperatures......Page 199
8.8.8 Carrier Gas Flow Rate Considerations for MS Detectors......Page 200
8.8.9 MS Maintenance......Page 201
8.8.10.1 Change in MS Sensitivity......Page 202
8.8.10.2 Excessive Noise or High Background in a MS......Page 203
8.8.10.3 Leaks in the MS......Page 204
9.2.1 Column Installation Steps......Page 205
9.2.3 Column Placement in the GC Oven......Page 206
9.2.4 Column Installation in the Injector......Page 207
9.2.6 Column Installation in the Detector......Page 208
9.2.7 Verifying Proper Column Installation and Detector Operation......Page 209
9.2.8.3 Conditioning the Column While Connected to the Detector......Page 211
9.2.9Setting the Carrier Gas Average Linear Velocity......Page 213
9.2.10Bleed Test......Page 214
9.2.11Injecting Column Test Sample......Page 215
9.3C olumn Ferrules......Page 217
9.4 Tightening Fittings......Page 218
9.5 Techniques for Measuring Column Insertion Distances......Page 219
9.6 Leak Detection......Page 220
10.1 Column Performance Testing......Page 221
10.2.2 Alcohols......Page 222
10.2.4 FAMEs......Page 223
10.3.2 Detectors......Page 224
10.3.4 Test Sample Concentration......Page 225
10.4 Grob Test......Page 226
10.5 Own Test Mixture......Page 227
10.6 When to Test a Column......Page 228
11.2.1 Causes of Column Breakage......Page 229
11.2.4 Recovery from Column Breakage......Page 230
11.3.2 Symptoms of Thermal Damage......Page 231
11.4.1 Causes of Oxygen Damage......Page 232
11.5.1 Causes of Chemical Damage......Page 233
11.5.1.2 Acids......Page 234
11.5.1.4 Organic Solvents and Water......Page 235
11.5.3 Prevention of Chemical Damage......Page 236
11.6.1Causes of Column Contamination......Page 237
11.6.2 Symptoms of Column Contamination......Page 239
11.6.4 Recovery from Contamination......Page 240
11.7.1 Solvent Rinse Kits......Page 241
11.7.2 Solvent Selection, Volumes and Flow Rates......Page 243
11.7.3 Conditioning the Column After Solvent Rinsing......Page 244
11.8.1 Deactivated Fused Silica Tubing......Page 245
11.8.3 Retention Gaps......Page 246
11.8.4 Unions......Page 247
11.10 Gas Impurity Traps......Page 249
11.12 Column Repair......Page 251
12.1 Introduction......Page 252
12.2.2 Checking the Obvious......Page 253
12.2.4 Looking for Trends, Patterns and Common Characteristics......Page 254
12.2.7 Moving from the General to the Specifi c......Page 255
12.2.9 Divide and Conquer......Page 256
12.3 Troubleshooting Tools......Page 257
12.4.1 Jumper Tube Test......Page 258
12.4.3 Check Out Column......Page 259
12.4.5 Static Pressure Check......Page 260
12.4.6 Column Test Samples......Page 261
13.2 Troubleshooting Checklist and Pre-Work......Page 262
13.3.1 Baseline Drift or Wander......Page 264
13.3.3 Spikes in the Baseline......Page 265
13.4.1 Tailing Peaks......Page 266
13.4.2 Fronting Peaks......Page 268
13.4.4 Flat Top Peaks......Page 269
13.5 Split Peaks......Page 270
13.6 Negative Peaks......Page 271
13.7 Excessively Broad Solvent Front......Page 272
13.9.1 Retention Time (tr) Change Only......Page 273
13.9.2 Retention Factor (k) Change......Page 274
13.10.2 All Peaks Change in Size......Page 275
13.10.3 Some Peaks Change in Size or Missing Peaks......Page 276
13.11 Extra or Ghost Peaks (Carryover)......Page 277
13.12 Rapid Column Deterioration......Page 278
13.13 Quantitation Problems......Page 279
Appendix A Terms
......Page 280
Appendix B Equations......Page 282
Appendix C Mass, Volume and Length Unit Conversions......Page 285
Appendix D Column Bleed Mass Spectra......Page 286
Appendix E The Basics of High Speed GC Using Small Diameter Columns......Page 292
Appendix F Basic Quantitative Capillary GC......Page 299
References......Page 336
Subject Index......Page 338
Related Titles......Page 346