Principles of Analytical Chemistry

Springer-Verlag Berlin Heidelberg GmbH

Miguel Valcarcel

Pri cip es of Analytical Chemistry A Textbook

With 132 Figures

, Springer

Miguel Valcarcel University of C6rdoba Department of Analytical Chemistry Avda. San Alberto Magno, s/n 14004 C6rdoba Spain

ISBN 978-3-642-62959-4

Library of Congress Cataloging-in-Publication Data Valcarcel Cases, Miguel.

Principles of analytical chemistry : a textbook 1 Miguel Valcarcel. p.cm.

Includes bibliographical references and index. ISBN 978-3-642-62959-4 ISBN 978-3-642-57157-2 (eBook) DOI 10.1007/978-3-642-57157-2 1. Chemistry, Analytic. 1. Ti tie.

QD75.2 .V35 2000 543-dc21 00-033829

This work is subject to copyright. AII rights are reserved, whether the whole or part of the material is con­cerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in other ways, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable for prosecution act under German Copyright Law.

© Springer-Verlag Berlin Heidelberg 2000 Originally published by Springer-Verlag Berlin Heidelberg New York in 2000 Softcover reprint of the hardcover 1 st edition 2000 The use of general descriptive names, registered names, trademarks, etc. in this publication does not imp­ly, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.

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Foreword

In 1988, Professor Julian Tyson published an informative little book entitled ''Analysis: What Analytical Chemists Do?' Professor Valcarcel's text could well be called "What Analytical Chemistry Is, What Analytical Chemists Do, and How to Do It Right:'

Thus, it is concerned with such things as what information is really needed, cost effectiveness considerations, tradeoffs in analyses, quality control and good analytical practice.

This book departs from traditional texts in concentrating on the structure of analytical chemistry, introducing students to analytical concepts, how to obtain reliable data, and how to interpret it. It does not teach the myriad of techniques and methodologies, which are reserved for the more conventional texts. It serves as an introductory text to be taught at the first year level or as a complement to conventional analytical chemistry texts. Practitioners of analytical chemistry will also find it useful for placing in context all that they do.

Professor Valcarcel takes a unique hierarchical approach to define and de­scribe concepts and analysis in general. The text builds on and integrates a number of concepts he has introduced over the years in the analytical chemistry literature (see, for example, Suggested Readings 1,2,3,7 and 9 in Chapter 1). The author makes generous use of relational figures throughout the text to aid the student in visualizing the concepts introduced in each chapter. The reader is recommended to look first at Figure 1.1 0, which nicely integrates and places in context the topics covered in the remainder of the text.

Each chapter is introduced with a list of learning objectives, a useful way to put the topics in perspective. There are boxed materials throughout that provide more detailed examples of the topics introduced. And at the ends of chapters are a series of "seminars:' Many are discussion oriented analysis problems, which can serve for individual study or group discussions, led, for example, by the instructor, for student centered learning. Others provide worked example problems. There are also numerous questions at the ends of the chapters aimed at testing the student's understanding of the concepts introduced in the chapter. Finally, a list of suggested reading is provided for each.

Chapter 3 has a useful Annex in which actual standard analytical methods are reproduced to illustrate the analytical process and approach for some specific ana­lyses. There is a useful glossary of terms at the end of the text. I recommend reading through this initially. It will give a quick flavor of topics to be covered, and provide a foundation for reading the text. Also, there is a helpful list of terms and symbols.

In order to enhance the flexibility of the text, and assist the instructor in adapting it for different learning environments or levels of instruction, Professor Valcarcel has provided a helpful list of topics to be selected at three levels, based on number of class hours.

VI Foreword

A student who has mastered the material. in this novel text will have an un­usual understanding of what ana:lyticailchemistry is, how it helps us understand our world, and how it improves 'what we do. It will serve as an excellent basis for studying the analytical method010'pes taught in quantitative analysis and instrumental analysis courses.

Gary D. Christian University of Washington Seattle, WA, USA

Preface

This book is intended to serve both as a generic introduction to Analytical Chemistry and as a body of essential analytical chemical knowledge. This grass­roots approach aims to convey the underlying integral teaching message of this dis­cipline in a proper manner in order to ensure effective, consistent learning leading to a solid analytical chemical background. As such, this textbook has been con­ceived as a tool of use to students undertaking Analytical Chemistry for the first time within the framework of a wide variety of undergraduate curricula. It aims to be a visiting card for this discipline. Because of their generic nature, the contents of this book must obviously be completed with the topics that constitute the typical core of other, high -quality textbooks of which this is by no means a competitor.

This is an atypical Analytical Chemistry textbook inasmuch as it provides no systematic description of analytical techniques (gravimetries, titrimetries, spectrometries, electro analysis) or methods - not even of ionic equilibria, improperly deemed by some "the fundamentals of analysis". Rather, it deals systematically with the true intrinsic fundamentals of Analytical Chemistry, which are those that make it an independent, self-contained science and distin­guish it unequivocally from other scientific and technical areas.

Few textbooks adopt such a generic approach to the subject, one that addres­ses topics such as analytical properties (Chapt. 2), standards and traceability (Chapt. 3), the analytical process (Chapt. 4), qualitative (Chapt. 5) and quanti­tative aspects (Chapt. 6), the analytical problem (Chapt. 7) and analytical quality (Chapter 8). These contents are intended to provide a solid foundation for sub­sequently acquired analytical chemical knowledge. Some of these topics are not easy to teach on an elementary level, so they are profusely illustrated with non­academic examples and consolidated with questions and seminars.

In a way, innovating involves leaping into the void, a risk that has consciously been assumed by the author. However, the pedagogical innovation implicit in this textbook has been tried and tested for six years in teaching Analytical Chemistry as a first-year subject of the Chemistry curriculum at the University of C6rdoba, Spain. I am deeply grateful to my partners in this venture, Professors Manuel Silva and Angel Rios, for their comments and expertise, which are reflected in this book in one way or another.

This novel conception is bound to meet with rejection by some Analytical Chemistry lecturers. It certainly departs considerably from the way they have traditionally approached first-time students of this subject. I just wish to ask those reluctant to adopt this new approach to reflect on it and let me know any­thing they may think fit about it. Their comments will no doubt help me enrich subsequent editions.

Because undergraduate curricula vary widely, the amount of time that can be devoted to this introduction to Analytical Chemistry also differs widely. By way

VIII Preface

of guidance, the table following this Preface establishes three different com­prehensiveness levels and suggests the book sections lecturers might want to include in each in developing their curricula.

The effort expended on writing this book was funded by Spain's CICyT with­in the framework of its programme for the development of undergraduate teaching materials. I wish to thank my colleagues Professors Carmen Camara, Miguel de la Guardia and Jose Manuel Pingarr6n for their thorough revision of its draft, which greatly helped me improve the initial scheme, and also first-year Chemistry student Mercedes L6pez Pastor. Also worthy of special acknowledge­ment here are Dr Marisol Cardenas, a fellow teacher at the Department of Analytical Chemistry of the University of C6rdoba, for her proofing assistance, Jose Manuel Membrives for preparing the typescript and artwork, and Antonio Losada for the English translation. This book would never have been published without the warm welcome and support of Peter Enders, Editor of Springer­Verlag.

Miguel Valcarcel C6rdoba, 1 July 2000

Recommendations for using the contents of this book at three different comprehensiveness levels

First level Second level Third level 6-8 Credits 4-6 Credits 2-3 Credits (60-80 hours) (40 - 60 hours) (20-30 hours)

Chapter 1 Unabridged (the less 1.1 Slightly abridged 1.1 Abridged generic concepts in (last part) 1.2 Abridged each section may be 1.2 Unabridged 1.3 Unabridged omitted, if necessary) 1.3 Unabridged 1.4 Highly abridged

1.4 Abridged (Exclude 1.4.4) (fundamental 1.5 Exclude concepts in each 1.6 Unabridged section) 1.7 Unabridged

1.5 Abridged 1.6 Unabridged 1.7 Unabridged

Chapter 2 Unabridged 2.1 Unabridged 2.1 Unabridged 2.2 Abridged 2.2 Highly abridged 2.3 Unabridged 2.3 Unabridged 2.4 early unabridged 2.4 Definitions only 2.5 early unabridged 2.5 Defmitions only 2.6 Abridged 2.6 Definitions only 2.7 Abridged 2.7 Highly abridged 2.8 Abridged 2.8 Exclude

Chapter 3 Unabridged 3.1 Unabridged 3.1 Unabridged 3.2 Nearly unabridged 3.2 Abridged 3.3 Unabridged 3.3 Abridged 3.4 Unabridged 3.4 Unabridged 3.5 Unabridged 3.5 Nearly unabridged 3.6.1 Unabridged 3.6 Section 3.6.1 only 3.6.2.6 Abridged

~.

Chapter 4 Unabridged 4.1 Slightly abridged 4.1 Slightly abridged 4.2 Unabridged 4.2 Unabridged 4.3 Unabridged 4.3 Slightly abridged 4.4 Unabridged 4.4 Abridged 4.5 Unabridged 4.5 Abridged 4.6 Abridged 4.6 Exclude

x Recommendations for using the contents of this book

Recommendations for using the contents of this book at three different comprehensiveness levels

First level Second level Third level 6-8 Credits 4- 6 Credits 2-3 Credits (60 - 80 hours) (40-60 hours) (20 - 30 hours)

Chapter 5 Unabridged 5.1 Unabridged 5.1 Slightly abridged 5.2 Unabridged 5.2 Abridged 5.3 Unabridged 5.3 Slightly abridged 5.4 Unabridged 5.4 Abridged 5.s Slightly abridged 5.5 Abridged 5.6 Slightly abridged 5.6 Abridged

Chapter 6 Unabridged 6.1 SHghtlyabridged 6.1 Abridged (last two (Sections 6.2.1.2 and 6.1.5 Unabridged sections excepted) 6.2.2.1 may be ex- 6.1.6 Unabridged 6.2.1.1 Slightly abridged cluded or abridged) 6.2.1.1 Unabridged 6.2.1.2 Exclude

6.2.1.2 Abridged 6.2.2.1 Exclude 6.2.2.1 Abridged 6.2.2.2 Slightly abridged 6.2.2.2 Unabridged 6.3 Abridged 6.3 Unabridged

Chapter 7 Unabridged 7.1 Abridged 7.1 Exclude 7.2 Abridged 7.2 Exclude 7.3 Unabridged 7.3 Highly abridged 7.4 Abridged 7.4 Highly abridged 7.5 Abridged 7.5 Highly abridged 7.6 Unabridged 7.6 Highly abridged 7.7 Abridged 7.7 Exclude

ChapterS Unabridged (slightly 8.1 Abridged Exclude abridged, focussing on S.2 Abridged the more relevant 8.3 Unabridged aspects of each section) 8.4 Abridged

8.5 Abridged 8.6 Abridged S.7 Abridged

Table of Contents

1 Introduction to Analytical Chemistry ........ . . . . . . . .. 1

1.1 Analytical Chemistry Today. . . . . . . . . . . . . . . . . . . . . .. 1 1.2 Analytical Chemical Information. . . . . . . . . . . . . . . . . . .. 6 l.3 Analytical Chemical References .................... 10 1.4 Essential Features of Analytical Chemistry . . . . . . . . . . . . .. 11

l.4.1 Basic Elements .......................... 12 l.4.2 Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . .. 13 l.4.3 Key Words . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14 l.4.4 Developments . . . . . . . . . . . . . . . . . . . . . . . . . .. 15 l.4.5 Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 17 l.4.6 Boundaries ............................ 18

l.5 Evolution of Analytical Chemistry . . . . . . . . . . . . . . . . . .. 19 1.6 Conceptual and Technical Hierarchies . . . . . . . . . . . . . . . .. 22 1. 7 Classifications .............................. 28 Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 34 Seminars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 36 Suggested Readings. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37

2 Analytical Properties ........................... 39

2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 40 2.2 The Chemical Metrological Hierarchy: Uncertainty and Trueness.. 41 2.3 Errors in Analytical Chemistry . . . . . . . . . . . . . . . . . . . .. 45 2.4 Capital Analytical Properties . . . . . . . . . . . . . . . . . . . . .. 52

2.4.1 Accuracy. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 53 2.4.2 Representativeness . . . . . . . . . . . . . . . . . . . . . . .. 54

2.5 Basic Analytical Properties . . . . . . . . . . . . . . . . . . . . . .. 56 2.5.1 Precision . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 57 2.5.2 Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 65 2.5.3 Selectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 69

2.6 Accessory Analytical Properties .................... 72 2.6.1 Expeditiousness . . . . . . . . . . . . . . . . . . . . . . . . .. 73 2.6.2 Cost-effectiveness. . . . . . . . . . . . . . . . . . . . . . . .. 73 2.6.3 Personnel-related Factors .................... 75

2.7 Relationships among Analytical Properties . . . . . . . . . . . . .. 75 2.7.1 Hierarchical Relationships . . . . . . . . . . . . . . . . . . .. 76 2.7.2 Foundation Relationships .................... 77 2.7.3 Contradictory Relationships . . . . . . . . . . . . . . . . . .. 77 2.7.4 Complementary Relationships. . . . . . . . . . . . . . . . .. 81

XII Table of Contents

2.8 Other Analytical Properties . 83 Questions .. . . . . . . . . . . . 87 Seminars: Numerical Problems . 89 Suggested Readings . . . . . . . . 100

3 Traceability: Reference Materials 101

3.1 Introduction . . . . . . . . . . . . 102 3.2 The Integral Concept of Traceability . . 102 3.3 Physical and Chemical Traceability. . . 105 3.4 Types of Standards and their Traceability . 107 3.5 Analytical Chemical Standards 112

3.5.1 Types. . . . . . . . . . . 113 3.5.2 General Properties ... 116 3.5.3 Preparation and Storage . . . . . . . . 119 3.5.4 Uses ............ . . . . . . . . 122

3.5.4.1 Calibration of Equipment and Methods 123 3.5.4.2 Evaluation of Analytical Processes 128

3.6 Specific Meanings of Traceability ..... 130 3.6.1 Traceability of an Analytical Result . 130 3.6.2 Traceability of a Sample (Aliquot) 132 3.6.3 Traceability of an Instrument . . . . 134 3.6.4 Traceability of a Sample Standard . . 134 3.6.5 Traceability of a Method . . . . . . . 135 3.6.6 Relationships among Traceability Meanings . . 135

Questions . . . . . . . 137 Seminars ....... 139 Suggested Readings 141

4 The Measurement Process in Chemistry ....... 143

4.1 Definition of Chemical Measurement Process .... 144 4.2 General Steps of a Chemical Measurement Process 147 4.3 Preliminary Operations . . . . . . . . . . . . 149

4.3.1 General Features 150 4.3.2 Sub-steps ..... 154 4.3.3 Sampling ............... 155 4.3.4 Sample Treatment .......... 161

4.4 Measurement and Transducing of the Analytical Signal 168 4.5 Signal Acquisition and Data Processing . . . . . 171 4.6 Validation of a Chemical Measurement Process . 173 4.7 Salient Current Trends 174 Annex I .. AnnexII .. Annex III .

177 182 186

Table of Contents XIII

Annex IV .................................... 189 AnnexV .................................... 190 Annex VI. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 Questions .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 Seminars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 Suggested Readings ............................. 199

5 Qualitative Aspects of Analytical Chemistry . . . . . . . . . . . . . 201

5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 5.2 The Binary Response .......................... 203

5.2.1 Types of Binary Response .................... 204 5.2.2 Quantitative Connotations . . . . . . . . . . . . . . . . . . . . 205 5.2.3 Analytical Features . . . . . . . . . . . . . . . . . . . . . . . . 208 5.2.4 Errors: False Positives and False Negatives ........... 210

5.3 Types of Qualitative Identification ................... 212 5.4 Standards and Calibration in Qualitative Analysis .......... 214 5.5 Classical Qualitative Analysis ...................... 215

5.5.1 General Notions ......................... 215 5.5.2 Types of Reagents ........................ 217 5.5.3 Analytical Schemes ........................ 221

5.5.3.1 Schemes without Group Separation .......... 222 5.5.3.2 Schemes with Group Separation ............ 224

5.6 Instrumental Qualitative Analysis ................... 229 5.6.1 General Notions ......................... 229 5.6.2 Static Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 5.6.3 Dynamic Systems ......................... 235

Questions .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 Seminars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 Suggested Readings ............................. 244

6 Quantitative Aspects of Analytical Chemistry . . . . . . . . . . .. 247

6.1 Fundamentals .............................. 248 6.1.1 Introduction ............................ 248 6.1.2 Analytical Properties . . . . . . . . . . . . . . . . . . . . . . . 249 6.1.3 Equipment and Method Calibration ............... 249 6.1.4 Classical and Instrumental Quantitative Analysis . . . . . . . 250 6.1.5 Quantitation Methodologies ................... 252 6.1.6 Expressing Quantitative Results ................. 253

6.2 Calculable Quantitation Methods ................... 256 6.2.1 Absolute Methods Involving no Analytical Standard ..... 257

6.2.1.1 Gravimetry . . . . . . . . . . . . . . . . . . . . . . . . 259 6.2.1.2 Coulometry . . . . . . . . . . . . . . . . . . . . . . . . 262

6.2.2 Absolute Methods Involving Analytical Standards ...... 263

XIV Table of Contents

6.2.2.1 Isotope Dilution Mass Spectrometry .......... 263 6.2.2.2 Titrimetry. . . . . . . . . . . . . . . . . . . . . . . . . 264

6.3 Relative Quantitation Methods ..................... 271 6.3.1 Interpolation and Extrapolation Methods ........... 271 6.3.2 Comparative Methods ...................... 275

Questions ............... . . . . . . . . . . . . . . . . . . . . 276 Seminars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 Suggested Readings ............................. 281

7 The Analytical Problem . . . . . . . . . . . . . . . . . . . . . . . . . . 283

7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 7.2 Meanings of "Problem" in Analytical Chemistry . . . . . . . . . . . 286 7.3 Integral Definition of the Analytical Problem ............. 286 7.4 Elements of the Analytical Problem .................. 289 7.5 Steps ofthe Analytical Problem-solving Process ........... 290

7.5.1 Identifying and Confirming the Information Required .... 291 7.5.2 Pinpointing the Analytical Information Required ....... 292 7.5.3 Planning the Analytical Approach ............... 294 7.5.4 Monitoring the Results ...................... 296 7.5.5 Implementing Corrective Actions ................ 297

7.6 Consistency Between Required Information and Supplied Information ............................... 297

7.7 The Analytical Problem in the Context of Quality .......... 299 Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301 Seminars ................................... 304 Suggested Readings ............................. 305

8 Analytical Chemistry and Quality ................. .. 307

8.1 Introduction ............................... 308 8.2 A Generic Approach to Quality . . . . . . . . . . . . . . . . . . . . . 310

8.2.1 Integral Definition of Quality .................. 310 8.2.2 Types of Quality. . . . . . . . . . . . . . . . . . . . . . . . . . 313 8.2.3 Quality Compromises ...................... 314 8.2.4 Structure of Quality ........................ 315 8.2.5 Benefits of Quality ........................ 316

8.3 General Aspects of Quality in Analytical Chemistry . . . . . . . . . 317 8.3.1 Types of Quality in Analytical Chemistry ........... 317 8.3.2 Quality and Analytical Properties . . . . . . . . . . . . . . . . 318 8.3.3 Quality and the Analytical Problem ............... 319

8.4 Quality Systems in the Analytical Laboratory . . . . . . . . . . . . . 319 8.4.1 Elements of Quality Assurance .................. 319 8.4.2 ISO Guide 25 (EN-45000) .................... 321 8.4.3 Good Laboratory Practices . . . . . . . . . . . . . . . . . . . . 323

Table of Contents xv

8.4.4 Specific Quality Systems Used in Analytical Chemistry . . . . 324 8.5 Analytical Quality Control ....................... 326 8.6 Assessment of Analytical Quality. . . . . . . . . . . . . . . . . . . . 327

8.6.1 Types of Assessment Systems .................. 327 8.6.2 Laboratory Accreditation . . . . . . . . . . . . . . . . . . . . . 330 8.6.3 Proficiency Testing . . . . . . . . . . . . . . . . . . . . . . . . 331

8.7 Supports of Analytical Quality Assurance . . . . . . . . . . . . . . . 334 8.8 Costs and Benefits of Analytical Quality Systems . . . . . . . . . . . 336 Questions .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 Seminars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Suggested Readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

Glossary of Terms ...... . . . . . . . . . . . . . . . . . . . . . . . . . 345

Symbols and Abbreviations used in the text .............. 367