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Über dieses Buch

MALDI-TOF mass spectrometry is one of the latest and most fascinating new developments in the analysis of organic compounds. Originally developed for the analysis of biomolecules, it has developed into one of the most powerful techniques for the characterization of synthetic polymers. This book describes the fundamentals of the MALDI process and the technical features of MALDI-TOF instrumentation. It reviews the application of MALDI-TOF for identification, chemical and molar mass analysis of synthetic polymers. With many examples, this monograph examines in detail experimental protocols for the determination of endgroups, the analysis of copolymers and additives, and the coupling of liquid chromatography and MALDI-TOF.

Inhaltsverzeichnis

Frontmatter

1. Introduction

Abstract
Though both mass spectrometry [1] and the synthesis of polymers [2] seem to be mature techniques — both date back to the beginning of the last century — they have both experienced steady development. The mutual influence of both techniques on each other has been slight but steadily growing and has led to new possibilities, one of which is Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI MS).
Harald Pasch, Wolfgang Schrepp

2. Mass Spectrometric Instrumentation

Abstract
This chapter describes the basic principles of mass spectrometry to allow a better assessment of the MALDI-technique. The typical procedure in mass spectrometry is as follows. After introducing the sample into the mass spectrometer, in the first step ions characteristic for the sample under investigation have to be created, i.e., an ion source is needed. Then the ions have to be separated according to their mass-to-charge ratio (m/z) which is the task of the (mass) analyzer. In the end the separated ions have to be detected and the signal displayed in a convenient form. Thus a mass spectrometer consists of the building blocks shown in Fig. 2.1.
Harald Pasch, Wolfgang Schrepp

3. Fundamentals of MALDI-TOF Mass Spectrometry

Abstract
In Chap. 2 the main mass spectroscopic instrumentation with relevance to the analysis of synthetic polymers has been described, demonstrating that there is no single means solving all problems. MALDI MS now adds another facet to the possibilities for mass spectroscopic characterization of polymers. The main features are the extremely high mass range in combination with a useful mass resolution as compared to all other MS techniques.
Harald Pasch, Wolfgang Schrepp

4. Identification of Polymers

Abstract
The type of polymer can be identified by determining the mass number of the repeat unit (r.u.) in the mass range where single oligomer resolution is achieved. This mass number is characteristic for a certain chemical composition and in most cases assignment is unambiguous. Very frequently, the type of polymer is already known before running a MALDI-TOF experiment. In these cases, the experiment aims at the analysis of possible by-products and various endgroups, and the determination of molecular heterogeneity. An overview on polymeric systems investigated so far by MALDI-TOF MS is given in Table 4.1.
Harald Pasch, Wolfgang Schrepp

5. Molar Mass Determination

Abstract
For polymeric materials, the molar mass or molecular size plays a critical role in determining the mechanical, bulk, and solution properties. These properties govern polymer processing, end-use performance, and stability. Therefore, determination of molar mass and molar mass distribution is of central interest in polymer analysis; see Chap. 1.
Harald Pasch, Wolfgang Schrepp

6. Analysis of Complex Polymers

Abstract
The chemical structure of a complex polymer is characterized by its chemical composition, the sequence of the monomer units in the polymer chain, the functionality, and the molar mass. Typically, polymer analysis has to deal with the overlaying effects of different types of molecular heterogeneity in one macromolecular system. As for functional homopolymers (telechelics, macromonomers) the molar mass distribution is superimposed by a functionality type distribution. Random or segmented copolymers consist of a multitude of molecules with different chain lengths and different chemical compositions. In the ideal case, such complex systems should be separated into individual oligomers, which then may be analyzed with respect to chain lengths, functional groups, and chemical composition.
Harald Pasch, Wolfgang Schrepp

7. Coupling of Liquid Chromatography and MALDI-TOF Mass Spectrometry

Abstract
From the very early stages of development of modern mass spectrometry, the value of its combination with chromatography was quickly recognized. The coupling of GC with MS was a natural evolution since they are both vapor phase techniques, and very quickly GC-MS has been accepted as a standard component of the organic analytical laboratory. It has taken considerably longer to achieve a satisfactory and all-purpose mode of HPLC-MS coupling. The difficulties with HPLC-MS were associated with the fact that vaporization of typically 1 ml/min from the HPLC translates into a vapor flow rate of approximately 500–1000 ml/min. Other difficulties related to the eluent composition as result of the frequent use of non-volatile modifiers, and the ionization of nonvolatile and thermally labile analytes. However, during the past few years commercial interfaces have been developed which have led to a broad applicability of HPLC-MS [1–3].
Harald Pasch, Wolfgang Schrepp

8. Recent Developments and Outlook

Abstract
This chapter describes some recent developments and chances for the future of MALDI MS. As already pointed out, the actual main driving force for technical advancements is the area of proteomics [1]. The requirements of high-throughput screening systems lead to considerable progress in automation, sample preparation, and interpretation. Without doubt the past decade has also seen a vivid development of MALDI applications to synthetic polymers but also limitations especially concerning polymers with broad molar mass distributions. Nevertheless nearly all items of MALDI MS are still under development.
Harald Pasch, Wolfgang Schrepp

Backmatter

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