R.P.W.Scott Liquid chromatography

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Transcript of R.P.W.Scott Liquid chromatography

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BOOK 3 Chrom-Ed Book SeriesRaymond P. W. Scott

LIQUID CHROMATOGRAPHY

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COPYRIGHT @2003 by LIBRARY4SCIENCE, LLC ALL RIGHTS RESERVED Neither this book or any part may be reduced or transmitted in any form or by any means, electronic or mechanical , including photocopying, microfilming, and recording or by any information storage and retrieved system without permission in writing from the publisher except as permitted by the in-user license agreement. World Wide Web http://www.library4science.com/

This eBook is protected by Copyright law and International Treaties. All rights are reserved. This book is covered by an End User Licensee Agreement (EULA). The full EULA may be seen at http://www.library4science.com/eula.html.

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Chrom-Ed Book SeriesBook 1 Book 2 Book 3 Book 4 Book 5 Book 6 Principles and Practice of Chromatography Gas Chromatography Liquid Chromatography Gas Chromatography Detectors Liquid Chromatography Detectors The Plate Theory and Extensions for Chromatography Columns Book 7 The Thermodynamics of Chromatography Book 8 The Mechanism of Retention Book 9 Dispersion in Chromatography Columns Book 10 Extra Column Dispersion Book 11 Capillary Chromatography Book 12 Preparative Chromatography Book 13 GC Tandem Systems Book 14 LC Tandem Systems Book 15 GC Quantitative Analysis Book 16 Ion Chromatography Book 17 Silica Gel and Its Uses in Chromatography Book 18 Thin Layer Chromatography Book 19 Chiral Chromatography Book 20 Bonded Phases Book 21 Chromatography Applications COPYRIGHT @2003 by LIBRARYFORSCIENCE, LLC ALL RIGHTS RESERVED

This eBook is protected by Copyright law and International Treaties. All rights are reserved. This book is covered by an End Us er Licensee Agreement (EULA). The full EULA may be seen at http://www.library4science.com/eula.html.

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Introduction ........................................................................................... 1 The Basic Liquid Chromatograph .......................................................... 2 The Gradient Programmer and the LC Pump ..................................... 4 The Gradient Programmer ............................................................. 4 The LC Pump .................................................................................... 6 The Pneumatic Pump ..................................................................... 6 Non-Return Valves ........................................................................ 8 The Syringe Pump ......................................................................... 9 The Rapid Refill Pump ................................................................ 12 The Twin-Headed Pump. ............................................................. 13 The Diaphragm Pump.................................................................. 14 The Sample Valve ........................................................................... 16 Column Switching ....................................................................... 19 Column Ovens .................................................................................... 20 Detectors ............................................................................................. 21 The UV Detector ............................................................................. 22 The Fixed Wavelength Detector ....................................................... 23 The Multi-Wavelength Detectors ..................................................... 26 The Multi-Wavelength Dispersive Detector ................................. 26 The Diode Array Detector ............................................................... 28 The Electrical Conductivity Detector ................................................... 29 The Fluorescence Detector................................................................... 32 The Refractive Index Detector ............................................................. 34 The Tridet Multi Functional Detector .................................................. 36 Liquid Chromatography Stationary Phases .......................................... 41 Silica Gel ......................................................................................... 42 The Preparation of Spherical Silica Gel ....................................... 43 The Structure of Silica Gel........................................................... 44 The Thermogravimetric Analysis of Silica Gel............................. 47 Bonded Phases ................................................................................ 49 The Synthesis of Bonded Phases .................................................. 49 Bonded Phase Synthesis by Reaction in a Solvent........................ 50 The Fluidized Bed Method for Bonded Phase Synthesis .............. 53 Choosing a Bonded Phase ............................................................... 56 Types of Bonded Phase ................................................................... 57 Oligomeric Phases ....................................................................... 58 Bulk Phases ................................................................................. 59This eBook is protected by Copyright law and International Treaties. All rights are reserved. This book is covered by an End User Licensee Agreement (EULA). The full EULA may be seen at http://www.library4science.com/eula.html.

5 Interactions Between 'Brush' and 'Bulk' Reverse Phases and Aqueous Solvents ........................................................................ 60 The Retention Properties of Bulk and Brush Phases. ........................... 63 Macroporous Polymers ........................................................................ 66 LC Mobile Phases ............................................................................... 68 Solvent/Solute Interactions with the Silica Gel Surface .................... 69 Solute Stationary Phase Interactions ............................................ 71 Solvent/Solute Interactions with the Reversed Phase Surface ........... 74 Molecular Interactions in the Mobile Phase ..................................... 76 Aqueous Solvent Mixtures............................................................... 78 Chiral Stationary Phases ...................................................................... 81 Macrocyclic Glycopeptide Phases .................................................... 83 Cyclodextrin .................................................................................... 89 Liquid Chromatography Applications .................................................. 93 References......................................................................................... 101

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1Introduction

Liquid chromatography (LC) was the first type of chromatography to be discovered and, in the form of liquid-solid chromatography (LSC), was originally used in the late 1890s by the Russian botanist, Tswett (1), to separate and isolate various plant pigments. The colored bands he produced on the adsorbent bed evoked the term chromatography (color writing) for this type of separation. Initially the work of Tswett was not generally accepted, partly due to the original paper being in Russian and thus, at that time, was not readily available to the majority of western chemists and partly due to the condemnation of the method by Willstatter and Stoll (2) in 1913. Willstatter and Stoll repeated Tswett's experiments without heeding his warning not to use too "aggressive " adsorbents as these would cause the chlorophylls to decompose. As a consequence, the experiments of Willstatter et al. failed and their published results, rejecting the work of Tswett, impeded the recognition of chromatography as a useful separation technique for nearly 20 years. In the late 1930s and early 1940s Martin and Synge introduced a form of liquid-liquid chromatography by supporting the stationary phase, in this case water, on silica gel in the form of a packed bed and used it to separate some acetyl amino acids. They published their work in 1941 (3) and in their paper recommended the replacement of the liquid mobile phase with a suitable gas, which would accelerate the transfer between the two phases and provide more efficient separations. Thus, the concept of gas chromatography was born. In the same paper in 1941, Martin and Synge suggested the use of small particles and high pressures in LC to improve the separation that proved to the critical factors that initiated the development of high performance liquid chromatography. To quote Martin's original paper, "Thus, the smallest H.E.T.P. (the highest efficiency) should be obtainable by using very small particles and a high pressure difference across the column".

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2 The statement made by Martin in 1941 contains all the necessary conditions to realize both the high efficiencies and the high resolution achieved by modern LC columns. Despite his recommendations, however, it took nearly fifty years to bring his concepts to fruition. Activity in the field of liquid chromatography was eclipsed in the 1950s by the introduction of gas chromatography and serious attempts were not made to imp