APPLICATIONS OF GAS CHROMATOGRAPHY Edited by Reza Davarnejad and Mahboubeh Jafarkhani Applications of Gas Chromatography Edited by Reza Davarnejad and Mahboubeh Jafarkhani Published by InTech Janeza Trdine 9, 51000 Rijeka, Croatia Copyright © 2012 InTech All chapters are Open Access distributed under the Creative Commons Attribution 3.0 license, which allows users to download, copy and build upon published articles even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. After this work has been published by InTech, authors have the right to republish it, in whole or part, in any publication of which they are the author, and to make other personal use of the work. Any republication, referencing or personal use of the work must explicitly identify the original source. 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Publishing Process Manager Daria Nahtigal Technical Editor Teodora Smiljanic Cover Designer InTech Design Team First published March, 2012 Printed in Croatia A free online edition of this book is available at www.intechopen.com Additional hard copies can be obtained from [email protected] Applications of Gas Chromatography, Edited by Reza Davarnejad and Mahboubeh Jafarkhani p. cm. ISBN 978-953-51-0260-1 Contents Preface VII Chapter 1 Gas Chromatography Application in Supercritical Fluid Extraction Process 1 Reza Davarnejad and Mostafa Keshavarz Moraveji Chapter 2 Interaction Parameters of Surfactant Mixtures by Inverse Gas Chromatography 17 Eleuterio Luis Arancibia, Pablo C. Schulz and Susana M. Bardavid Chapter 3 Applications of Chromatography Hyphenated Techniques in the Field of Lignin Pyrolysis 41 Shubin Wu, Gaojin Lv and Rui Lou Chapter 4 Degradation Phenomena of Reforming Catalyst in DIR-MCFC 65 Kimihiko Sugiura Chapter 5 Recent Strategies in Organic Reactions Catalyzed by Phase Transfer Catalysts and Analyzed by Gas Chromatography 83 P. A. Vivekanand and Maw-Ling Wang Chapter 6 POP and PAH in Bizerte Lagoon, Tunisia 117 Trabelsi Souad, Ben Ameur Walid, Derouiche Abdekader, Cheikh Mohamed and Driss Mohamed Ridha Preface This book presents a critical review of various chromatography techniques for a limited number of processes. Most techniques are illustrated by examples. The processes described are necessarily limited to those which appear to the authors to have the greatest validity and practical use. Wherever possible, we have included recommendations delineating the best techniques for analyzing each sample. Recommended techniques are often illustrated by detailed examples. Although the book is intended to serve primarily the practicing engineer, especially the process or chemical engineer, other engineers (such as environmental engineers) and chemists concerned with analyzing techniques may find it useful. Most new techniques are still empirical in nature, although there are often theoretical bases for the correlation; wherever possible, the theory is outlined to provide the user with the foundation of the proposed chromatography techniques. Special thanks are due to all respectful authors for their excellent contributions to this book and to Ms. Martina Durovic and Ms. Daria Nahtigal for extensive assistance and support. Reza Davarnejad and Mahboubeh Jafarkhani Department of Chemical Engineering, Faculty of Engineering, Arak University Iran 1 Gas Chromatography Application in Supercritical Fluid Extraction Process Reza Davarnejad* and Mostafa Keshavarz Moraveji Department of Chemical Engineering, Faculty of Engineering, Arak University, Iran 1. Introduction There are two types of application for gas chromatography (GC) in the supercritical fluid extraction process. Gas chromatography is a type of supercritical extraction apparatuses which can separate a component from a multi-component mixture during supercritical extraction. Therefore, this application can be the alternative to conventional gas chromatography, which needs high temperatures for the evaporation of the feed mixture and for liquid chromatography, where liquid solvents may be replaced. This process results in a different transport velocity along the stationary phase for different molecules. Molecules having weak interaction forces with the stationary phase are transported quickly while others with strong interactions are transported slowly. Beside the interactions with the stationary phase, the solvent power of the mobile phase determines the distribution of the components. Furthermore, supercritical gases have a high solvent power and exert this solvent power at low temperatures. Another application of GC in supercritical fluid extraction is consideration and analysis of extraction product. The obtained products from various types of supercritical apparatuses (such as phase equilibrium and rate test apparatus) should be analyzed. However, different types of analyzer can be used but, the conventional GC with a suitable column has widely been recommended. Although several columns for detecting a lot of components have been designed and fabricated by some companies but due to lacking of suitable columns for some components or unclear peaks obtained from some columns, an extra process (such as esterification of the fractionated fish oil) before GC analyze is sometimes required. In this application, the samples obtained from the supercritical extraction apparatus are not under pressure or their pressures have broken down by a damper (in online GC). In this chapter both types of GC application in supercritical fluid extraction with examples will be illustrated. 2. Gas chromatography apparatus In supercritical fluid chromatography (SFC) the mobile phase is a supercritical gas or a near critical liquid. Compared to gas chromatography (GC), where a gas is under ambient * Corresponding Author 2 Applications of Gas Chromatography pressure (for example in the second type of apparatus applied in supercritical process), and liquid chromatography (LC), where a liquid is used as mobile phase, the solvent power of the liquid mobile phase in SFC can be varied by density, e.g., by pressure changes at constant temperature. Solubility increases in general with pressure under supercritical conditions of the mobile phase, temperature sensitive compounds can be processed. The chromatographic separation can be carried out at constant pressure (isobaric operation) or with increasing pressure (pressure programmed). In addition, temperature can be varied. SFC has one more adjustable variable for optimization of elution than GC or LC (Brunner, 1994). A supercritical fluid has properties similar to a gas and also similar to a liquid. While density and solvent power may be compared to those of liquids, transport coefficients are more those of a gas. SFC, because of its mobile phase, can cover an intermediate region between GC and LC, as illustrated in Figure 1 with respect to density and diffusion coefficient. For preparative and production scale operations, SFC has the advantage of easy separation of mobile phase from separated compounds. A disadvantage is that strongly polar and ionic molecules are not dissolved by supercritical gases, which can be advantageously used in SCF (Brunner, 1994). Fig. 1. Areas for the different mobile phases in chromatographic separations with respect to component properties (Schoenmakers and Uunk, 1987). Most gases which can be used in SFC are non-polar. Therefore, polar substances of a feed mixture can only be eluted by adding a polar modifier. Polar gases like ammonia or sulfur dioxide are reactive compounds under pressure the equipment must be able to withstand corrosive conditions. On the other hand, carbon dioxide is easy to handle and safe. Polar modifiers, which are easier to handle than ammonia or sulfur dioxide may instead be applied. To make effective use of the possibilities of SFC, allowable pressures should be high.