Planar chromatography - mass spectrometry 9781498705899, 1498705898

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CHROMATOGRAPHIC SCIENCE SERIES

VOLUME 110

Planar ChromatographyMass Spectrometry

Edited by

Teresa Kowalska Mieczysław Sajewicz Joseph Sherma

Dedication This book is dedicated to the memory of Friedrich (“Fritz”) Geiss, who passed away on February 14, 2015, nine days before his 83rd birthday. Excellent reviews of Dr. Geiss’ education and work history, as well as contributions to the ield of thinlayer chromatography (TLC), were given in editorials on the occasion of his 80th birthday published in the Journal of Planar Chromatography—Modern TLC (25(3), 193, 2012) and Acta Chromatographica (24(2), 143–144, 2012). We would like to focus here on the two indispensible TLC books that he wrote. In 1972, Dr. Geiss’ book Die Parameter der Duennschictchromatographie was published by Vieweg in German, and the second edition in English titled Fundamentals of ThinLayer Chromatography (Planar Chromatography) was published in 1987 by Huethig. In the preface to the German edition, Dr. Geiss wrote that during his work in TLC that began in 1960 with attempts to separate a mixture of hydrocarbons, he and his colleague Helmut Schlitt were concerned for many years with the problem of factors that inluence TLC. His aim for the book was to build a bridge between the laboratory handbooks of TLC and the fundamental books of chromatography available at that time in order to translate the fundamentals into daily practice and realize TLC’s real potential to become a reliable and nonempirical method. He addressed for the irst time the theory and fundamentals necessary to understand the layer– analyte–mobile phase interactions and predict the most favorable conditions for successful and reproducible TLC separations.

In the preface to the English edition, Dr. Geiss stated that he found the information on fundamentals and reproducibility obsolete, incorrect, or misleading in TLC books available in 1987, and that he was writing a book that “is not theoretical but describes what happens in TLC, or what the practitioner should know that happens, and how he can control what happens.” He provided information he believed was needed to understand and predict optimal conditions for TLC in order to provide adequate and reproducible separations and reliable quantiication. He was the only author up to that time to attempt to explain the complex situation occurring inside the TLC development tank with multicomponent mobile phases. In his foreword to Dr. Geiss’ English edition, Lloyd R. Snyder, author of the renowned fundamentals book Principles of Adsorption Chromatography, wrote that among Dr. Geiss’ accomplishments in his two books was to develop and make available a better understanding of the complex phenomena occurring in the “simple” technique of TLC, organize the irst practical theory of TLC, improve conventional TLC, provide information leading to important new TLC techniques based on his studies of pre-equilibration of the TLC plate and mobilephase demixing, and present the irst valid equation and practical instructions for the safe transfer of separation from layer to column. Dr. Snyder noted that in the updated edition were comprehensive accounts of method development and selectivity optimization in TLC and high-performance TLC (HPTLC), interrelationship of separation by TLC and column HPLC, importance of band broadening in TLC, and instrumentation needed for quantitative work. Over the last few years, Dr. Geiss was considering an updated and expanded third edition of his book to include the latest technical innovations, such as modern instrumentation and

chemometrics and embrace all possibilities and enhanced potentials of modern TLC. He kept up to date on these advances by regularly attending numerous chromatography meetings even after stopping experimental work upon retirement. One of the technical advances Dr. Geiss would have undoubtedly included enthusiastically in his new edition is TLC–mass spectrometry, the topic of this book. Sadly, the new edition was not realized as a further invaluable and lasting contribution of Dr. Geiss to the ield. Dr. Geiss’ books have had enormous impact on the TLC work of the editors during our careers, and we are pleased to dedicate this book as a heartfelt, although inadequate, token of thanks for the critical contributions on behalf of all chromatographers of this brilliant colleague. Teresa Kowalska Mieczysław Sajewicz Joseph Sherma

Contents Preface....................................................................................................................xvii Editors .....................................................................................................................xix Contributors ......................................................................................................... xxiii

SECTION I Materials, Instrumentation, and Techniques of Planar ChromatographyMass Spectrometry Chapter 1

Overview of the Field of TLC–MS and Contents of the Book ............ 3 Teresa Kowalska, Mieczysław Sajewicz, and Joseph Sherma

Chapter 2

Applicability of Commercial and Noncommercial Thin Layers for Mass Spectrometric Detection...................................................... 15 Fred Rabel

Chapter 3

The CAMAG TLC–MS Interface ...................................................... 35 Joseph Sherma and Jacob Strock

Chapter 4

Principles of Mass Spectrometry Imaging Applicable to ThinLayer Chromatography....................................................................... 59 Przemysław Mielczarek, Anna Bodzon´ -Kułakowska, Jerzy Silberring, and Piotr Suder

Chapter 5

Mass Spectrometry Applicable to Electrophoretic Techniques ......... 67 Anna Drabik, Joanna Ner, Przemysław Mielczarek, Piotr Suder, and Jerzy Silberring

Chapter 6

Selection of Ionization Methods of Analytes in the TLC–MS Techniques .......................................................................................... 81 Michał Cegłowski and Grzegorz Schroeder

Chapter 7

Interfacing TLC with Laser-Based Ambient Mass Spectrometry ....... 105 Sychyi Cheng and Jentaie Shiea

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Chapter 8

Contents

TLC–MS Analysis Using Solvent Elution of Compounds from Chromatographic Media.......................................................... 123 Alen Albreht and Irena Vovk

Chapter 9

Recording of Mass Spectra from Miniaturized Layers (UTLC–MS) .... 141 Tim T. Häbe and Gertrud E. Morlock

SECTION II Practical Applications of Planar Chromatography-Mass Spectrometry Methodology Chapter 10 Strategies of Coupling Planar Chromatography to HPLC–MS ....... 173 Claudia Oellig and Wolfgang Schwack Chapter 11 Drug Analysis by TLC–DESI MS ................................................... 199 Anna Bodzon´ -Kułakowska, Przemysław Mielczarek, Piotr Suder, and Jerzy Silberring Chapter 12 Application of TLC and Plasma-Based Ambient MS in Bioanalytical Sciences......................................................................205 Marek Smoluch, Przemysław Mielczarek, Michał Cegłowski, Grzegorz Schroeder, and Jerzy Silberring Chapter 13 TLC/MALDI MS for the Analysis of Lipids ................................... 213 Jürgen Schiller, Beate Fuchs, Rosmarie Süß, Yulia Popkova, Hans Griesinger, Katerina Matheis, Michaela Oberle, and Michael Schulz Chapter 14 Application of TLC–MS to Drug Photodegradation Studies ........... 233 Urszula Hubicka, Jan Krzek, Anna Maślanka, and Barbara Żuromska-Witek Chapter 15 Combination of Thin-Layer Chromatography with Laser Desorption Ionization and Electrospray Ionization–Mass Spectrometric Techniques for Screening of Organic Compounds ......255 Suresh Kumar Kailasa, Jigneshkumar V. Rohit, and Hui-Fen Wu Chapter 16 Application of TLC–MS to Analysis of Drugs of Abuse................. 281 Bruno D. Sabino, Amadeu Cardoso Jr., and Wanderson Romão

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Chapter 17 TLC–MS Analysis of Carotenoids, Triterpenoids, and Flavanols in Plant Extracts and Dietary Supplements ...................................... 305 Irena Vovk and Alen Albreht Chapter 18 TLC/MALDI MS of Carbohydrates ................................................ 327 Katharina Lemmnitzer, Rosmarie Süß, and Jürgen Schiller Chapter 19 Spontaneous Chiral Conversion and Peptidization of Amino Acids Traced by Means of TLC–MS ............................................... 345 Agnieszka Godziek, Anna Maciejowska, Mieczysław Sajewicz, and Teresa Kowalska

Preface This book is devoted to a relatively new approach to chemical analysis in general, and to separation science in particular, the combination of thin-layer chromatography (TLC) and high-performance TLC (HPTLC), among the simplest, most cost-effective, and yet very well-performing techniques for determining complex mixtures of compounds, with mass spectrometry (MS), a sophisticated and relatively expensive spectrometric technique that enables rapid identiication of separated chemical species. TLC–MS coupling can signiicantly facilitate identiication of mixture components, which is particularly important, for example, in forensic studies; identiication of drug metabolites, breakdown products, and impurities; and identiication of biologically active components in phytochemical samples, especially in cases when analytical standards are for certain reasons unavailable (e.g., they are not traded commercially or are too expensive). Quantiication of identiied compounds can also be obtained by using the TLC–MS combination. As one- and two-dimensional gel electrophoresis are often classiied as planar chromatographic techniques and are increasingly more exploited in proteomic and molecular biology studies, and for medical diagnostic purposes as well, the book also covers electrophoretic–MS methods and applications. The book consists of 19 chapters that provide general information about the existing possibilities of coupling TLC with MS, as well as a selection of important and diverse practical applications of the TLC–MS technique to a variety of analytical separation/identiication/quantiication problems written by worldwide experts in the ield from the United States, Europe, Asia, and South America. It is the irst published book on the topic of TLC–MS, and it comprehensively covers all aspects of the hyphenated method for separation/identiication/quantiication of a wide variety of analytes in a wide range of sample matrices. It contains information on principles, methods, and instrumentation of all ofline and online modes of TLC–MS as well as practical examples of applications originating from laboratories in which it has been in use for some time. It provides necessary information for the use of TLC–MS in laboratories that have appropriate MS equipment but have not yet employed it to enhance the analytical power of TLC. The use of a relatively inexpensive commercial TLC–MS interface/mass spectrometer system is also described for those laboratories without the beneit of MS instrumentation at this time. The contents of the book are especially useful for those laboratories that employ TLC for rapid screening of herbal nutritional supplement and medicinal samples in order to conirm the identity, origin, or possible adulteration by use of “ingerprinting” with TLC–MS. It encourages adoption or greater use of the hyphenated method with enhanced analytical capabilities by graduate students, industry professionals, researchers, academics, and regulatory analysts, and it introduces the ield to junior and senior undergraduate students.

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The editors would like to thank Barbara Glunn, senior editor, chemistry, and Jill Jurgensen, senior project coordinator, editorial project development, for their support during all aspects of the proposal and editorial processes. We also thank the chapter authors for their invaluable contributions. Teresa Kowalska Mieczysław Sajewicz Joseph Sherma

Editors Teresa Kowalska earned an MSc in chemistry from the former Pedagogical High School in Katowice, Poland, in 1968, a PhD in physical chemistry from the University of Silesia, Katowice, Poland, in 1972, and a DSc in physical chemistry from the Maria Curie-Skłodowska University in Lublin, Poland, in 1988. In the 1974–1975 school year, Professor Kowalska stayed for 12 months as a British Council postdoctoral fellow at the Chemistry Faculty of Salford University, Salford, Lancashire, United Kingdom, under the supervision of the late Professor Hans Suschitzky, head of the Organic Chemistry Department there. Professor Kowalska has authored and coauthored approximately 300 original research and review papers in approximately 30 different peer-reviewed chemistry journals, 16 invited book chapters, and approximately 500 conference papers (both lectures and posters) included in the programs of scientiic conferences at home and abroad (also on numerous personal invitations). Moreover, Professor Kowalska coedited with Professor Joseph Sherma Preparative Layer Chromatography and Thin Layer Chromatography in Chiral Separations and Analysis, and with Professor Monika Waksmundska-Hajnos and Professor Sherma Thin Layer Chromatography in Phytochemistry, all published in the Chromatographic Science Series by CRC Press/Taylor & Francis Group. Last, Professor Kowalska (together with Professor Mieczysław Sajewicz) acts as coeditor-in-chief of the international chromatography journal Acta Chromatographica, published by Akademiai Kiado, Budapest, Hungary. She also acts as an editorial board member for several chromatography journals, including the Journal of Chromatographic Science (published by Oxford University Press), the Journal of Planar Chromatography—Modern TLC (published by Akademiai Kiado), and the online journal Chromatography Research International (published by Hindawi Press). On an invitation of approximately 20 internationally recognized analytical chemistry and separation science journals, Professor Kowalska has prepared several hundred peer reviews of manuscript submissions. Professor Kowalska’s main research interests focus on the applications of the thinlayer, high-performance liquid and gas chromatography to physicochemical problems (such as extraction of thermodynamic information from gas chromatographic data, enantioseparations mechanisms, and tracing the nonlinear chemical reactions with the aid of liquid chromatographic techniques). She is also interested in analytical applications of liquid chromatographic techniques to food chemistry (mainly to the chemistry of medicinal plants and meat products). In the ield of nonlinear reaction mechanisms, Professor Kowalska has established fruitful collaboration with the world’s leading research group in this area, headed by Professor Irving R. Epstein from the Chemistry Department of Brandeis University, Waltham, Massachusetts. In parallel with her research, Professor Kowalska has been an academic teacher for over four decades and in this capacity she has taught undergraduate courses in general chemistry and undergraduate and postgraduate courses in fundamentals and applications of the chromatographic techniques. Professor Kowalska has xix

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supervised approximately 80 MSc and 13 PhD theses (in the ield of analytical chemistry and chromatographic science), and also served as a jury member for approximately 40 doctorates at home and abroad. She is actively involved in the EU undergraduate students international exchange program Socrates, encouraging her own students to pursue a one-semester training experience in a foreign institution, and also hosting foreign undergraduate students and postdoctoral fellows in her laboratory. For her continuous and dedicated engagement in teaching chemistry, Professor Kowalska has been awarded many times at the local and national levels. Mieczysław Sajewicz earned an MSc and a PhD in chemistry from the University of Silesia, Katowice, Poland, in 1978 and 1989, respectively. The main area of his MSc and PhD studies was analytical chemistry and, more precisely, application of gas chromatography to studying factors governing separation quality (e.g., isomerism of analytes, polarity of stationary phases, and working parameters of gas chromatographic system as a whole). In 2013, Professor Sajewicz earned a DSc in pharmacy from Collegium Medicum, Jagiellonian University, Kraków, Poland. His DSc dissertation focused on spontaneous nonlinear processes (oscillatory chiral conversion and oscillatory condensation) running in aqueous and nonaqueous solutions of profen drugs and the other low-molecular-weight chiral carboxylic acids (derived from acetic, propionic, and butyric acid). Professor Sajewicz has authored and coauthored over 150 original research papers and over 350 conference papers, presented at conferences and congresses at home and abroad. Moreover, he has coauthored one encyclopedia entry in Encyclopedia of Chromatography (2nd edition revised and expanded; 2005) and two book chapters (Chapter 2 in Preparative Layer Chromatography, edited by Teresa Kowalska and Joseph Sherma with CRC Press/Taylor & Francis Group in 2006, and Chapter 9 in Thin Layer Chromatography in Chiral Separations and Analysis, also edited by Teresa Kowalska and Joseph Sherma with CRC Press/Taylor & Francis Group in 2007). Since 1992, Professor Sajewicz has been an editorial board member for Acta Chromatographica, and in 2002, he became coeditor-in-chief of the same journal. He also acts as an editorial board member for the analytical chemistry section of The Scientiic World Journal. Since 1980, Professor Sajewicz has been a member of the Organizing Committee of the annual all-Polish Symposium on Chromatographic Methods of Investigating the Organic Compounds, organized by the Institute of Chemistry, University of Silesia, Katowice, Poland, and has been cochairman of the Scientiic and Organizing Committee of the same scientiic event since 2002. Professor Sajewicz has wide teaching experience at the undergraduate and graduate university levels. He has run courses in chemical calculus, several laboratory courses in planar, high-performance liquid and gas chromatography, and MSc lecture courses on selected chromatographic techniques and on applications thereof to environmental analysis. He has supervised and cosupervised approximately 70 MSc theses, and he has cosupervised 4 PhD theses. For his continuous and dedicated engagement in teaching chemistry, Professor Sajewicz has been awarded at the local and national levels.

Editors

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Joseph Sherma earned a BS in chemistry from Upsala College, East Orange, New  Jersey, in 1955 and a PhD in analytical chemistry from Rutgers, The State University, New Brunswick, New Jersey, in 1958 under the supervision of the renowned ion exchange chromatography expert Wm. Rieman III. Professor Sherma is currently John D. and Francis H. Larkin professor emeritus of chemistry at Lafayette College, Easton, Pennsylvania; he taught courses in analytical chemistry for more than 40 years, was head of the Chemistry Department for 12 years, and continues to supervise research students at Lafayette. During sabbatical leaves and summers, Professor Sherma did research in the laboratories of the eminent chromatographers Dr. Harold Strain, Dr. Gunter Zweig, Professor James Fritz, and Professor Joseph Touchstone. Professor Sherma has authored, coauthored, edited, or coedited more than 750 publications, including research papers and review articles in approximately 55 different peer-reviewed analytical chemistry, chromatography, and biological journals; approximately 30 invited book chapters; and more than 65 books and U.S. government agency manuals in the areas of analytical chemistry and chromatography. In addition to his research in the techniques and applications of thin layer chromatography (TLC), Professor Sherma has a very productive interdisciplinary research program in the use of analytical chemistry to study biological systems with Bernard Fried, Kreider Professor Emeritus of Biology at Lafayette College, with whom he wrote Thin Layer Chromatography (1st–4th editions) and edited the Handbook of Thin Layer Chromatography (1st–3rd editions), both published by Marcel Dekker, Inc., as well as editing Practical Thin Layer Chromatography for CRC  Press. Professor Sherma wrote with Dr. Zweig a book titled Paper Chromatography for Academic Press and the irst two volumes of the Handbook of Chromatography series for CRC Press, and coedited with him 22 more volumes of the chromatography series and 10 volumes of the series Analytical Methods for Pesticides and Plant Growth Regulators for Academic Press. After Dr. Zweig’s death, Professor Sherma edited ive additional volumes of the chromatography handbook series and two volumes in the pesticide series. The pesticide series was completed under the title Modern Methods of Pesticide Analysis for CRC Press with two volumes coedited with Dr. Thomas Cairns. Three books on quantitative TLC and advances in TLC were edited jointly with Professor Touchstone for Wiley-Interscience. For the CRC/ Taylor & Francis Group Chromatographic Science Series, Professor Sherma coedited with Professor Teresa Kowalska Preparative Layer Chromatography and Thin Layer Chromatography in Chiral Separations and Analysis; with Professor Kowalska and Professor Monika Waksmundska-Hajnos, Thin Layer Chromatography in Phytochemistry; with Professor Waksmundska-Hajnos, High Performance Liquid Chromatography in Phytochemical Analysis; and with Professor Lukasz Komsta and Professor Waksmundska-Hajnos, Thin Layer Chromatography in Drug Analysis. A volume titled High Performance Liquid Chromatography in Pesticide Residue Analysis, coedited with Professor Tomasz Tuzimiski in the Chromatographic Science Series, was published in 2015. Professor Sherma served for 23 years as editor for residues and trace elements of the Journal of AOAC International and is currently that journal’s acquisitions editor. He has guest edited with Professor Fried 16 annual special issues on TLC of the Journal of Liquid Chromatography & Related Technologies and regularly

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guest edits special sections of issues of the Journal of AOAC International on speciic subjects in all areas of analytical chemistry. For 12 years he also wrote an article on modern analytical instrumentation for each issue of the Journal of AOAC International. Professor Sherma has written biennial reviews of planar chromatography published in the American Chemical Society journal Analytical Chemistry, Journal of AOAC International, and Central European Journal of Chemistry since 1970 and biennial reviews of pesticide analysis by TLC since 1982 in the Journal of Liquid Chromatography & Related Technologies and the Journal of Environmental Science and Health, Part B. He is now on the editorial boards of the Journal of Planar Chromatography—Modern TLC; Acta Chromatographica; Journal of Environmental Science and Health, Part B; and Journal of Liquid Chromatography & Related Technologies. Professor Sherma was the recipient of the 1995 ACS Award for Research at an Undergraduate Institution sponsored by Research Corporation. The irst 2009 issue, Volume 12, of the journal Acta Universitatis Cibiensis, Seria F, Chemia was dedicated in honor of Professor Sherma’s teaching, research, and publication accomplishments in analytical chemistry and chromatography.

Contributors Alen Albreht Laboratory for Food Chemistry National Institute of Chemistry Ljubljana, Slovenia

Agnieszka Godziek Institute of Chemistry University of Silesia Katowice, Silesia, Poland

Anna Bodzoń-Kułakowska Department of Biochemistry and Neurobiology AGH University of Science and Technology Kraków, Poland

Hans Griesinger Merck KGaA Darmstadt, Hesse, Germany

Amadeu Cardoso Jr. Contraprova Análises Ensino e Pesquisas Ltda. Rio de Janeiro, Brazil Michał Cegłowski Department of Supramolecular Chemistry Adam Mickiewicz University in Poznań Poznań, Poland Sychyi Cheng Department of Chemistry National Sun Yat-Sen University Kaohsiung, Taiwan Anna Drabik Department of Biochemistry and Neurobiology AGH University of Science and Technology Kraków, Poland Beate Fuchs Institute of Medical Physics and Biophysics University of Leipzig Leipzig, Saxony, Germany

Tim T. Häbe Institute of Nutritional Sciences and Interdisciplinary Research Center (IFZ) Justus Liebig University Giessen Giessen, Hesse, Germany Urszula Hubicka Collegium Medicum Jagiellonian University Kraków, Poland Suresh Kumar Kailasa Department of Applied Chemistry S. V. National Institute of Technology Surat, Gujarat, India Teresa Kowalska Institute of Chemistry University of Silesia Katowice, Silesia, Poland Jan Krzek (Deceased) Collegium Medicum Jagiellonian University Kraków, Poland Katharina Lemmnitzer Institute of Medical Physics and Biophysics University of Leipzig Leipzig, Saxony, Germany xxiii

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Anna Maciejowska Institute of Chemistry University of Silesia Katowice, Silesia, Poland Anna Maślanka Collegium Medicum Jagiellonian University Kraków, Poland Katerina Matheis Merck KGaA Darmstadt, Hesse, Germany Przemysław Mielczarek Academic Centre for Materials and Nanotechnology AGH University of Science and Technology Kraków, Poland Gertrud E. Morlock Institute of Nutritional Sciences and Interdisciplinary Research Center (IFZ) Justus Liebig University Giessen Giessen, Hesse, Germany Joanna Ner Department of Biochemistry and Neurobiology AGH University of Science and Technology Kraków, Poland Michaela Oberle Merck KGaA Darmstadt, Hasse, Germany Claudia Oellig Institute of Food Chemistry University of Hohenheim Baden-Württemberg, Stuttgart, Germany

Contributors

Yulia Popkova Institute of Medical Physics and Biophysics University of Leipzig Leipzig, Saxony, Germany Fred Rabel ChromHELP, LLC Woodbury, New Jersey Jigneshkumar V. Rohit Department of Applied Chemistry S. V. National Institute of Technology Surat, Gujarat, India Wanderson Romão Department of Chemistry Federal University of Espírito Santo Vitória, Espírito Santo, Brazil Bruno D. Sabino Institute of Criminalistic Carlos Éboli and Contraprova Análises Ensino e Pesquisas Ltda. Rio de Janeiro, Brazil Mieczysław Sajewicz Institute of Chemistry University of Silesia Katowice, Silesia, Poland Jürgen Schiller Institute of Medical Physics and Biophysics University of Leipzig Leipzig, Saxony, Germany Grzegorz Schroeder Department of Chemistry Adam Mickiewicz University in Poznań Poznań, Poland

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Michael Schulz Merck KGaA Darmstadt, Hasse, Germany Wolfgang Schwack Institute of Food Chemistry University of Hohenheim Baden-Württemberg, Stuttgart, Germany Joseph Sherma Department of Chemistry Lafayette College Easton, Pennsylvania Jentaie Shiea Department of Chemistry National Sun Yat-Sen University Kaohsiung, Taiwan Jerzy Silberring Department of Biochemistry and Neurobiology AGH University of Science and Technology Kraków, Poland and Centre of Polymer and Carbon Materials Polish Academy of Sciences Zabrze, Poland Marek Smoluch Department of Biochemistry and Neurobiology AGH University of Science and Technology Kraków, Poland

Jacob Strock Department of Chemistry Lafayette College Easton, Pennsylvania Rosmarie Süß Institute of Medical Physics and Biophysics University of Leipzig Leipzig, Saxony, Germany Piotr Suder Academic Centre for Materials and Nanotechnology AGH University of Science and Technology Kraków, Poland Irena Vovk Laboratory for Food Chemistry National Institute of Chemistry Ljubljana, Slovenia Hui-Fen Wu Department of Chemistry National Sun Yat-Sen University Kaohsiung, Taiwan Barbara Żuromska-Witek Collegium Medicum Jagiellonian University Kraków, Poland

Section I Materials, Instrumentation, and Techniques of Planar ChromatographyMass Spectrometry

1

Overview of the Field of TLC–MS and Contents of the Book Teresa Kowalska, Mieczysław Sajewicz, and Joseph Sherma

CONTENTS 1.1 Overview of Thin-Layer Chromatography–Mass Spectrometry......................3 1.2 Organization of the Book .................................................................................7 References ................................................................................................................ 13

1.1

OVERVIEW OF THIN-LAYER CHROMATOGRAPHY–MASS SPECTROMETRY

Although the history of thin-layer chromatography (TLC) dates back to the analysis of plant tinctures on aluminum oxide layers with methanol mobile phase by Ismailov and Shraiber in 1938 as chronicled by Sherma and Morlock in a published chronology [1], the irst report on TLC coupled with mass spectrometry (MS) was not until 1977 by Issaq [2]. He eluted separated zones on a layer using the CAMAG Eluchrom instrument, designed and described in the literature in 1975 [1], and eluates were introduced into a mass spectrometer through a Pyrex inlet probe. It is useful to comment on correct use of nomenclature in the ield of liquid chromatography (LC). The acronym HPLC is almost universally used to denote column high-performance liquid chromatography, but high-performance TLC (HPTLC) involves the use of a liquid mobile phase and technically belongs to the category of HPLC. Similarly, the acronym LC–MS is almost always used for hyphenation of column LC (HPLC, ultra-performance liquid chromatography [UPLC, used for Waters Corp. Acquity systems with columns containing