Spectrometric Titrations volume Analytical Chemistry

435 Pages·1989·151.1 MB·English

by  Jürgen Polster

J. Polster, H. Lachmann
Analysis of
Chemical Equilibria
1. Polster, H. Lachmann
Spectrometric Titrations
©VCHVerlagsgesellschaftmbH,D-6940Weinheim(FederalRepublicofGermany),1989
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ISBN3-527-26436-1(VCHVerlagsgesellschaft) ISBN0-89573-570-9(VCHPublishers)
Jiirgen Polster
Heinrich Lachmann
Spectrometric Titrations
Analysis of
Chemical Equilibria
ProfessorDr. Jurgen Polster Dr. HeinrichLachmann t
Lehrstuhlfur Allgemeine Chemie Institutfur Physikalischeund
undBiochemie TheoretischeChemie
TechnischeUniversitatMunchen UniversitatTiibingen
D-8050Freising-Weihenstephan
FederalRepublicofGermany
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LibraryofCongressCardNo. appliedfor
BritishLibraryCataloguinginPublicationData
Polster,Jtirgen
Spectrometrictitrations.
1.Chemicalanalysis,Spectroscopy
1.TitleII.Lachmann,Heinrich
543'0858
ISBN3-527-26436-1
CIP-TitelaufnahmederDeutschenBibliothek:
Polster,Jiirgen:
SpectrometricTitrations:AnalysisofChemicalEquilibria/JtirgenPolster;HeinrichLachmann.
Weinheim;Basel(Switzerland);Cambridge;NewYork,NY:
VCH,1989
ISBN3-527-26436-1
(Weinheim...)
ISBN0-89573-570-9
(Cambridge...)
NE:Lachmann,Heinrich
©VCHVerlagsgesellschaft,D-6940Weinheim(FederalRepublicofGermany),1989
Allrightsreserved(includingthoseoftranslationintootherlanguages).Nopartofthisbookmaybereproducedin
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PrintedintheFederalRepublicofGermany
Dedicated to
Professor
HEINZ MAUSER,
our distinguished teacher
Preface
Upon hearing the word titration most analytical chemists think first of the technique
introduced by Gay-Lussac for the quantitative determination of a dissolved material,
in which a titration endpoint is established with the aid ofacolored indicator. It has
more recently been recognized, however, that there are other sorts of problems that
lend themselves to investigation by titration. Indeed, it is now common to utilize
titration techniques in the search for fundamental informationregarding a wide variety
ofequilibrium systems. Thus, ifstepwisechanges are madein theposition ofan equi
librium through the addition of successive portions ofan appropriate titrant, physical
characteristics of the altered system at each "step" may be defined in terms of a
recording of appropriate potentiometric or spectroscopic parameters. In many cases
the resulting record permits accurate computation of an equilibrium constant, the
quantity that is usually ofgreatestinterest.
Equilibria playa fundamental role in a wide array ofproblems in both chemistry
and biochemistry, so it is little wonder that equilibria also constitute a fertile field of
investigation for chemists, biochemists, biologists, pharmacologists, toxicologists, and
others. These researchers represent the target audience for our monograph.
The purpose of the book is to summarize recently developed methods for the
spectroscopic analysis ofchemical equilibria. The methods themselves are applicable
to virtually any spectroscopic technique that produces an output signal linearly de-
.pendent upon the concentrations of certain solution components, a criterion met by
UV/VIS, IR, fluorescence, CD, ORD, NMR, and ESR. Methods ofevaluation appli
cable to each ofthese types of spectroscopy are dealt with explicitly in the text. The
term spectrometry implies the recording of spectra of any type, so we elected to
underscore the generality of this experimental approach by assigning our book the
broad titleSpectrometricTitration.
The book itselfis divided into three parts, each of which may be read independ
ently. Nevertheless, since Part I provides the relevant theoretical and methodological
background, as well as definitions for key technical terms, we recommend that it be
read first.
VIII Preface
Part II is a systematic examination of an assorment oftitration systems, including
equilibria ofthe acid-base, metal complex, association (or bonding), and redox types.
The treatment is limited to homogeneous phases; problems posed by precipitation or
other phase separations are deliberately ignored. The central theme ofeach chapter is
a search for answers to two questions: (1) what types of information can one derive
solely on the basis of spectrometric measurements, and (2) how can this information
be correlated with electrometric (e.g. pH) data in order to establish equilibrium con
stants?
PartIII is devoted to experimental considerations related to UVNIS, fluorescence,
CD/ORD, IR, Raman, and NMR, as well as the application of these tools to
spectrometric titration. At least one concrete example is provided with respect to
each ofthe corresponding spectroscopic methods. The literature is covered fully until
theend of 1986. The bookconcludes with an appendix listing two computerprograms,
EDIA and TIFIT, which we havefound useful in interpreting ourdata.
The starting point for the analytical methods described is the general theory of
isosbestic points, originallydeveloped byHeinzMauserfor the study ofclosed thermal
and photochemical reactions. Mauser also introduced a series of graphic techniques
[absorbance (A-) diagrams, absorbance difference (AD-) diagrams, absorbance dif
ference quotient (ADQ-) diagrams] that provide rapid, simple, yeteffective means for
establishing the number oflinearly independent steps constituting a reaction system.
The first application ofthis methodology to the study ofacid-base equilibria, general
ized to include various types of spectroscopy, was by Heinrich Lachmann, who
recognized the value of this route to establishing the number of independent steps
characterizing a titration system. In a subsequent collaboration with Rudiger Blume
the authors were then able to introduce anumber ofadditional techniques for spectro
metric determination ofthe pKvalues that characterize acid-base equilibria.
The authors are deeply indebted to theirdistinguished mentor, Prof. HeinzMauser,
to whom this book is dedicated, for many critical and stimulating discussions and for
his continued support oftheirresearch efforts over a great many years. Special thanks
are also due to Dr. Gabriele Lachmann, who shares the responsibility for editing those
chapters (chapters 1-4, 6, 10-12, and 16-19) prepared originally by her husband, a
task necessitated by his sadly premature and untimely death.
We also wish to thank Prof. Rudiger Blume for his many valuable contributions
and for placing at ourdisposal much useful material; Prof. GunterJung, who provid
ed us with experimental data and spectra; and Drs. Friedrich Gabber and Klaus
Willamowski for numerous suggestions and contributions, including the basis for the
two computer programs EDIA and TIFIT. Thanks are due as well to Christina Nagy
Huch-Hallwachs, Jutta Konstanczak and Brigitte Moratz for their technical assis
tance.
We are particularly grateful to Prof. Hanns-Ludwig Schmidt for his continued and
active interest in and support of our work. We have also appreciated the cooperation
of VCH Verlagsgesellschaft-particularly that of Dr. Weller-in providing a critical
Preface IX
review ofthetranslated manuscriptand thenensuring its swiftpublication. Finally, we
wish to thank Prof. Claus Bliefert, who carried the burden ofdesktop publishing this
book to an excellent end, and Dr. William Russey (Juniata College, Huntingdon, PA)
for his rapid and skillful translation of the German manuscript, and for his useful
suggestions and observations.
Jiirgen Polster
Contents
Part I The Theoretical and Methodological Basis of Spectrometric
Titration
1 Basic Principles and the Classification ofTitration Methods 3
1.1 Definitions . . . . . . . . . . . . . . . 3
1.2 The Classification of Spectrometric Titration Methods 5
Literature . . . . . . . . . . . . . . . 7
2 Graphic Treatment ofthe Data from a Spectrometric Titration 9
Literature 12
3 Basic Principles of Multiple Wavelength Spectrometry as
Applied to Titration Systems . . . . . 13
3.1 Generalized Lambert-Beer-Bouguer Law . 13
3.2 Matrix-Rank Analysis ofa Titration System 15
3.2.1 Numeric Matrix-Rank Analysis . . . . 15
3.2.2 Graphic Methods ofMatrix-Rank Analysis 16
Literature . . . . . . . . . . . 20
4 Thermodynamic and Electrochemical Principles of
Spectrometric Titration Systems 23
Literature 25
Part II The Formal Treatment and Evaluation ofTitration Systems
Analysis ofChemical Equilibria
5 The Goal ofa Spectrometric Titration 29