Microwave induced plasma analytical spectrometry

263 Pages·2011·10.322 MB·English

by  Krzysztof J Jankowski, Edward Reszke

Microwave Induced Plasma Analytical Spectrometry
RSC Analytical Spectroscopy Monographs
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Neil W. Barnett, Deakin University, Victoria, Australia
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Titles in the Series:
1: Flame Spectrometry in Environmental Chemical Analysis: A Practical
Guide
2: Chemometrics in Analytical Spectroscopy
3: Inductively Coupled and Microwave Induced Plasma Sources for Mass
Spectrometry
4: Industrial Analysis with Vibrational Spectroscopy
5: Ionization Methods in Organic Mass Spectrometry
6: Quantitative Millimetre Wavelength Spectrometry
7: Glow Discharge Optical Emission Spectroscopy: A Practical Guide
8: Chemometrics in Analytical Spectroscopy, 2nd Edition
9: Raman Spectroscopy in Archaeology and Art History
10: Basic Chemometric Techniques in Atomic Spectroscopy
11: Biomedical Applications of Synchrotron Infrared Microspectroscopy
12: Microwave Induced Plasma Analytical Spectrometry
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Microwave Induced Plasma
Analytical Spectrometry
Krzysztof J. Jankowski
Department of Analytical Chemistry, Warsaw University of Technology,
Warsaw, Poland
Edward Reszke
Ertec-Poland, Wroclaw, Poland
RSCAnalyticalSpectroscopyMonographsNo.12
ISBN:978-1-84973-052-5
ISSN:2041-9732
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Preface
Microwave frequencies have been used for plasma generation for many
years. Advancements in the understanding of microwave plasmas (MWPs)
have led to improvements in the design of the components that comprise the
instruments used for MWP sources. As a result, MWPs have been success-
fully used as vaporization/excitation sources for optical emission spectro-
metry or as vaporization/ionization sources for mass spectrometry. Over the
past 20 years, MWP analytical spectrometry has grown from being a niche
technique to becoming a promising tool in the analytical laboratory. In par-
ticular, microwave induced plasma optical emission spectrometry (MIP-OES)
has proved to be an essential technique for the direct analysis of chromato-
graphic eluates. The aim of this monograph is to inform the reader of the
present status of MWP analytical spectrometry by providing an overview of
the technique. In more recent years, several commercial MWP-based analy-
tical instruments have appeared on the market, and an increasing interest in
the benefits which can be gained from the use of MWPs is observed. During
this time, a number of key papers were published, instrumentation was sig-
nificantly improved, and some technical limitations of MWP operation were
solved. Today, MWP spectrometry, particularly atomic emission, is a highly
developed measurement technique. Obviously, MWP analytical spectrometry
is now entering its mature phase of development, with a large number of
applications for a wide variety of sample types. This book provides a com-
prehensive discussion of the major aspects involved in MWP-based analytical
spectrometry, with emphasis on practical issues, and documents the latest
achievements in MWP spectrometry to stimulate their use on a wider scale in
analytical and research laboratories. However, it is surprising that despite
this remarkable growth, most of the research and practice of analytical spec-
trometry has been centred almost exclusively around inductively coupled
plasmas (ICPs), even although it is clear that MWPs can offer significant
advantages for certain applications. There are several sources of specific,
RSCAnalyticalSpectroscopyMonographsNo.12
MicrowaveInducedPlasmaAnalyticalSpectrometry
ByKrzysztofJ.JankowskiandEdwardReszke
rTheRoyalSocietyofChemistry2011
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v
vi Preface
detailed information about the MWP-OES technique available. However, up
to now the MWP method was generally presented as an alternative plasma
source and there was lack of a monograph concerning MWP analytical spec-
trometry. This book is designed for use by academics and postgraduates
embarking on work in the field of MWP source spectrometry, ICP/MWP
users, analysts and research groups who want to configure their own plasma
spectrometry setup, and manufacturers of plasma spectrometers and MWP
devices. The monograph will also be a useful source of information for those
seeking to interface various sample introduction techniques with plasmas and
for all those who would like to know more about the technique. The physical
and chemical characteristics of the various MWP sources and sample intro-
duction techniques available are all discussed and how these characteristics
affect the design of the parts of the MWP setup, with inclusion of some very
recent work with MWP sources carried out in our research group and that
described by others.
AgeneralintroductiongiveninChapter1concentratesonthefundamentals
of MWP formation under different experimental conditions, presents basic
physical characteristics of the MWP discharge, and discusses various spectro-
scopictechniquespertinenttotheoperationofaMWP.InChapter2,ageneral
descriptionoftheinstrumentationrequiredforMWPanalyticalspectrometryis
presented,includingthebenefitsandlimitationsofMWPdischarges.Chapter3
addresses the art and science of MWP design and highlights very recent
advances in the field, presenting a new advanced classification of microwave
plasmasources.Chapter3alsoconsidersvariousMWPsources,includingvery
recent approaches for generating an annular-shaped plasma, a rotating field
three-phase plasma and a microwave frequency glow discharge. The imple-
mentation of these approaches, however, requires an understanding of the
fundamental theory behind microwave plasma generation and maintenance.
There then follows in Chapter 4 a review of microwave safety precautions.
Chapter5dealswithsomesimple,yetfundamental,conceptsregardingoptical
emission spectrometryandspectraobtainedbyMIPs,includingthemostused
emission lines in MIP-OES. Chapters 6 to 8 deal with the various techniques
used for transporting samples into the plasma, probably the most challenging
area for MWP-OES operators, including the introduction of gaseous, liquid
and solid samples. Each sampling technique is described with respect to prin-
ciples, instrumentation,operatingparametersandlimitations inthecontextof
MWP-OES. Then the specific applications of MIP-OES are presented. In
Chapters 9 and 10, more detail regarding the MWP-OES technique is given,
including the optimization of operating parameters and analytical method
development. Then follows additional information about line selection,
instrument maintenance and performance verification, and trouble shooting.
Analytical characteristics of MWP-OES are included. The chapter also com-
paresanalyticalperformanceindicesforvariousplasmasources.Chapter11is
devoted to the applications of MWP-OES for a wide variety of sample types.
Finally, Chapter 12 briefly describes non-emission MWP spectroscopic
Preface vii
techniques, including some specific analytical applications of the MWP-MS
method.
We are indebted to all our MIP-OES and MS teachers and colleagues who
have provided significant contributions to the field. Their efforts behind the
backgroundtothisbookhavebroughtustoabetterunderstandingofthebasic
science of MIP-based techniques and has stimulated further studies. As a
consequence, we came to the conclusion and after discussions we had been
advised to understand that there was a new need for the publication of a
comprehensive reference book on the theory and practice of the field. We are
grateful to Dr Andrzej Ramsza for his expert assistance in setting up the sci-
entific level of the work and his helpful comments on the draft manuscript.
SpecialthanksareduetoProfessorsRamonBarnesandGaryHieftjeforsome
helpful suggestions and comments that encouraged us to write this book.
Finally, we would also like to thank the publishers, who have, with great
perseverance, enthusiasm and patience, brought this book to fruition.
Krzysztof J. Jankowski
Edward R. Reszke

Contents
Chapter 1 An Introduction to Microwave Plasma Spectrometries 1
1.1 Introduction 1
1.1.1 Historical Background 2
1.1.2 The Present Status of Microwave Plasma
Spectrometry 4
1.2 Energy Flow between Microwave Plasma and
Analyte 5
1.2.1 Microwave Power Absorption by the
Plasma 5
1.2.2 Plasma–Sample Interaction 6
1.2.3 Analyte Excitation and Ionization 7
1.2.4 Summary: Energy Flow Diagram 8
1.3 Microwave Plasma Generation 9
1.3.1 MicrowavePlasmaGeometries(Configurations) 12
1.3.2 Power Density versus Plasma Stability 13
1.4 BasicPhysicalCharacteristicsofaMicrowavePlasma
Discharge 15
1.5 Spectroscopic Techniques Employing Microwave
Induced Plasmas 17
References 18
Chapter 2 Instrumentation for Microwave Induced Plasma Optical
Emission Spectrometry 23
2.1 The Components of a Microwave Induced Plasma
Optical Emission Spectrometry System 23
2.2 Microwave Induced Plasma Torches 26
2.2.1 Torch Designs 27
RSCAnalyticalSpectroscopyMonographsNo.12
MicrowaveInducedPlasmaAnalyticalSpectrometry
ByKrzysztofJ.JankowskiandEdwardReszke
rTheRoyalSocietyofChemistry2011
PublishedbytheRoyalSocietyofChemistry,www.rsc.org
ix