Dean Rood

The Troubleshooting and Maintenance Guide for Gas Chromatographers

Fourth, Revised and Updated Edition

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Dean RoodThe Troubleshooting and Maintenance Guide for Gas Chromatographers

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18072007 Knowledge for Generations

Each generation has its unique needs and aspirations. When Charles Wiley fi rst opened his small printing shop in lower Manhattan in 1807, it was a generation of boundless potential searching for an identity. And we were there, helping to defi ne a new American literary tradition. Over half a century later, in the midst of the Second Industrial Revolution, it was a generation focused on building the future. Once again, we were there, supplying the critical scientifi c, technical, and engineering knowledge that helped frame the world. Throughout the 20th Century, and into the new millennium, nations began to reach out beyond their own borders and a new international community was born. Wiley was there, ex panding its operations around the world to enable a global exchange of ideas, opinions, and know-how.

For 200 years, Wiley has been an integral part of each generations journey, enabling the fl ow of information and understanding necessary to meet their needs and fulfi ll their aspirations. Today, bold new technologies are changing the way we live and learn. Wiley will be there, providing you the must-have knowledge you need to imagine new worlds, new possibilities, and new opportunities.

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William J. Pesce Peter Booth WileyPresident and Chief Executive Offi cer Chairman of the Board

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Dean Rood

The Troubleshooting and Maintenance Guide for Gas Chromatographers

Fourth, Revised and Updated Edition

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All books published by Wiley-VCH are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.

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2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form by photoprinting, microfi lm, or any other means nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifi cally marked as such, are not to be considered unprotected by law.

Typesetting Manuela Treindl, LaaberPrinting Strauss GmbH, MrlenbachBinding Litges & Dopf GmbH, HeppenheimWiley Bicentennial Logo Richard J. Pacifi co

Printed in the Federal Republic of GermanyPrinted on acid-free paper

ISBN 978-3-527-31373-0

The Author

Dean Rood968 Glide Ferry Way DriveSacramento, CA 95831USA

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V

Preface

Even though gas chromatography (GC) is considered a very mature and highly developed technology, advances continue to be made in the areas of hardware, electronics, software and columns. In some cases, these advances have reduced the occurrence of problems and made their detection easier and more certain. In other cases, greater complexity has been introduced with its own set of problems and solutions. Regardless of the age or complexity of the GC instrument, many of the same problems occur and the underlying causes are often the same. In addition, the guidelines and techniques used to care and maintain the instruments and columns are the same.

With this thought in mind, much of the core information in this edition does not differ signifi cantly from the previous one; however, there are a number of noteworthy additions and enhancements. The majority of the fi gures are new and improved especially in the injector and detector chapters. A complete section on pressure and fl ow programmable injectors has been added. Due to its popularity and specifi c requirements, an Appendix on high speed GC using small diameter columns is new to this edition. Column, hardware, carrier gas and sample considerations and issues are presented in a concise and direct format to ensure successful high speed GC applications. Finally, an extensive Appendix on the basics of quantitative GC is new and relatively unique. This Appendix covers important quantitation defi nitions, calibration curves, the selection and use of quantitation techniques such as internal and external standards, and several standard preparation techniques. Numerous examples are provided to aid in understanding.

The information contained in this book encompasses nearly 25 years of in-depth experience in the fi eld of GC along with the wisdom passed along from 1000s of personal interactions with GC practitioners around the world. It is often practical information mixed with a touch of theory such as presented and discussed within these pages that most often proves to be the most useful and helpful.

Sacramento, CA, March 2007 Dean Rood

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VII

Contents

Preface V

Intentions and Introduction 1

1 Introduction to Capillary Gas Chromatography 31.1 What Is Gas Chromatography? 31.2 What Types of Compounds Are Suitable for GC Analysis? 31.3 The Basic Parts of a Gas Chromatograph 41.3.1 Gas Supply and Flow Controllers 41.3.2 Injector 51.3.3 Capillary Column and Oven 51.3.4 Detector 61.3.5 Data System 61.4 The Chromatogram 61.5 The Mechanism of Compound Separation 81.5.1 A Simple Description of the Chromatographic Process 81.5.2 A Detailed Description of the Chromatographic Process 91.6 Factors Affecting Separation 111.6.1 Stationary Phase 111.6.2 Compound Structure 121.6.3 Column Temperature 12

2 Basic Defi nitions and Equations 142.1 Why Bother? 142.2 Peak Shapes 142.2.1 Peak Width (W) 142.2.2 Peak Symmetry 142.3 Retention 162.3.1 Retention Time (tr) 162.3.2 Adjusted Retention Time (tr) 162.3.3 Retention Factor (k) 162.3.4 Retention Index (I) 182.4 Phase Ratio ( ) 192.5 Distribution Constant (KC) 20

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VIII Contents

2.5.1 KC and Column Dimensions 212.5.2 KC and Column Temperature 212.6 Column Effi ciency 212.6.1 Number of Theoretical Plates (N) 222.6.2 Height Equivalent to a Theoretical Plate (H) 222.6.3 Effective Theoretical Plates (Neff) and Effective Plate Heights (Heff) 232.6.4 Precautions When Using Theoretical Plates 232.7 Utilization of Theoretical Effi ciency (UTE%) 242.8 Separation Factor ( ) 252.9 Resolution (R) 252.10 Trennzahl (TZ) 272.11 Column Capacity 28

3 Capillary GC Columns: Tubing 303.1 Fused Silica Capillary Columns 303.2 Fused Silica Tubing 303.3 Outer Coating 323.4 Other Tubing Materials 323.5 Polyimide Fused Silica Tubing Bending Stress 33

4 Capillary GC Columns: Stationary Phases 344.1 Stationary Phases 344.2 Types of Stationary Phases 354.2.1 Polysiloxanes or Silicones 354.2.2 Arylene-Modifi ed Polysiloxanes 374.2.3 Polyethylene Glycols 374.2.4 Porous Layer Stationary Phases 384.3 Characteristics of Stationary Phases 394.3.1 Bonded and Cross-linked Stationary Phases 394.3.2 Stationary Phase Polarity 394.3.3 Stationary Phase Selectivity 404.4 Stationary Phase Interactions 414.4.1 Dispersion Interaction 414.4.2 Dipole Interaction 424.4.3 Hydrogen Bonding Interaction 434.4.4 When There are Multiple Interactions 444.5 Stationary Phase Equivalencies 454.6 Column Temperature Limits 464.7 Column Bleed 474.7.1 What is Column Bleed? 474.7.2 Measuring Column Bleed 484.7.3 Sensitivity Considerations 494.7.4 Detector Considerations 494.7.5 Minimizing Column Bleed 504.8 Selecting Stationary Phases 50

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IXContents

5 Capillary GC Columns: Dimensions 535.1 Introduction 535.2 Column Length 535.2.1 Column Length and Effi ciency/Resolution 535.2.2 Column Length and Retention 575.2.3 Column Length and Pressure 575.2.4 Column Length and Bleed 585.2.5 Column Length and Cost 585.2.6 Selecting Column Length 585.3 Column Diameter 595.3.1 Column Diameter and Effi ciency/Resolution 595.3.2 Column Diameter and Retention 625.3.3 Column Diameter and Pressure 625.3.4 Column Diameter and Bleed 635.3.5 Column Diameter and Capacity 635.3.6 Column Diameter