refac Preface A currently taught, the introductory course in analytical chemistry emphasizes quantitative(and sometimes qualitative) methods of analysis coupled with a heavy dose of equilibrium chemistry. Analytical chemistry, however, is more than equilib rium chemistry and a collection of analytical methods; it is an approach to solving hemical problems. Although discussing different methods is important, that dis- cussion should not come at the expense of other equally important topics. The intro- ductory analytical course is the ideal place in the chemistry curriculum to explore topics such as experimental design, sampling, calibration strategies, standardization, optimization, statistics, and the validation of experimental results. These topics are important in developing good experimental protocols, and in interpreting experi mental results. If chemistry is truly an experimental science, then it is essential that all chemistry students understand how these topics relate to the experiments they conduct in other chemistry courses. Currently available textbooks do a good job of covering the diverse range of wet and instrumental analysis techniques available to chemists. Although there is some disagreement about the proper balance between wet analytical techniques, such as gravimetry and titrimetry, and instrumental analysis techniques, such as spec trophotometry, all currently available textbooks cover a reasonable variety of tech niques. These textbooks, however, neglect, or give only brief consideration to, obtaining representative samples, handling interferents, optimizing methods, ana- zing data, validating data, and ensuring that data are collected under a state of st: tistical control In preparing this textbook, I have tried to find a more appropriate balance between theory and practice, between“ classical”and“ modern” methods of analysis, between analyzing samples and collecting and preparing samples for analysis, and between analytical methods and data analysis. Clearly, the amount of material in this textbook exceeds what can be covered in a single semester; it,s my hope, however, that the diversity of topics will meet the needs of different instructors, while, per suggesting some new The anticipated audience for this textbook includes students majoring in chem- try, and students majoring in other science disciplines(biology, biochemistry, ted obtaining a stronger background in chemical analysis. It is particularly appropriate for chemistry majors who are not planning to attend graduate school, and who often do not enroll in those advanced courses in analytical chemistry that require physical hemistry as a pre-requisite. Prior coursework of a year of general chemistry is assumed Competence in algebra is essential; calculus is used on occasion, however, its presence is not essential to the materials treatment
As currently taught, the introductory course in analytical chemistry emphasizes quantitative (and sometimes qualitative) methods of analysis coupled with a heavy dose of equilibrium chemistry. Analytical chemistry, however, is more than equilibrium chemistry and a collection of analytical methods; it is an approach to solving chemical problems. Although discussing different methods is important, that discussion should not come at the expense of other equally important topics. The introductory analytical course is the ideal place in the chemistry curriculum to explore topics such as experimental design, sampling, calibration strategies, standardization, optimization, statistics, and the validation of experimental results. These topics are important in developing good experimental protocols, and in interpreting experimental results. If chemistry is truly an experimental science, then it is essential that all chemistry students understand how these topics relate to the experiments they conduct in other chemistry courses. Currently available textbooks do a good job of covering the diverse range of wet and instrumental analysis techniques available to chemists. Although there is some disagreement about the proper balance between wet analytical techniques, such as gravimetry and titrimetry, and instrumental analysis techniques, such as spectrophotometry, all currently available textbooks cover a reasonable variety of techniques. These textbooks, however, neglect, or give only brief consideration to, obtaining representative samples, handling interferents, optimizing methods, analyzing data, validating data, and ensuring that data are collected under a state of statistical control. In preparing this textbook, I have tried to find a more appropriate balance between theory and practice, between “classical” and “modern” methods of analysis, between analyzing samples and collecting and preparing samples for analysis, and between analytical methods and data analysis. Clearly, the amount of material in this textbook exceeds what can be covered in a single semester; it’s my hope, however, that the diversity of topics will meet the needs of different instructors, while, perhaps, suggesting some new topics to cover. The anticipated audience for this textbook includes students majoring in chemistry, and students majoring in other science disciplines (biology, biochemistry, environmental science, engineering, and geology, to name a few), interested in obtaining a stronger background in chemical analysis. It is particularly appropriate for chemistry majors who are not planning to attend graduate school, and who often do not enroll in those advanced courses in analytical chemistry that require physical chemistry as a pre-requisite. Prior coursework of a year of general chemistry is assumed. Competence in algebra is essential; calculus is used on occasion, however, its presence is not essential to the material’s treatment. xii Preface Preface 1400-Fm 9/9/99 7:38 AM Page xii
Preface Key Features of This Textbook Key features set this textbook apart from others currently available. A stronger emphasis on the evaluation of data. Methods for characterizing chemical measurements, results, and errors(including the propagation of errors)are included. Both the binomial distribution and normal distribution are presented, and the idea of a confidence interval is developed. Statistical methods for evaluating data include the t-test(both for paired and unpaired data), the F-test, and the treatment of outliers. Detection limits also are discussed from a statistical perspective. Other statistical methods, such a ANOVA and ruggedness testing, are presented in later chapters. Standardizations and calibrations are treated in a single chapter. Selecting the most appropriate calibration method is important and, for this reason, the ethods of external standards, standard additions, and internal standards are gathered together in a single chapter. A discussion of curve-fitting, including the statistical basis for linear regression(with and without weighting)also is included in this chapter. More attention to selecting and obtaining a representative sample. The design of a statistically based sampling plan and its implementation are discussed earlie and in more detail than in other textbooks. Topics that are covered include how to obtain a representative sample, how much sample to collect, how many samples to collect, how to minimize the overall variance for an analytical method, tools for collecting samples, and sample preservation The importance of minimizing interferents is emphasized. Commonly used methods for separating interferents from analytes, such as distillation, masking, and solvent extraction, are gathered together in a single chapter Balanced coverage of analytical techniques. The six areas of analytical techniques-gravimetry, titrimetry, spectroscopy, electrochemistry, chromatography, and kinetics--receive roughly equivalent coverage, meeting the needs of instructors wishing to emphasize wet methods and those emphasizing instrumental methods Related methods are gathered together in a gle chapter encouraging students to see the similarities between methods, rather than focusing on their differences An emphasis on practical applications. Throughout the text applications from organic chemistry, inorganic chemistry, environmental chemistry, clinical chemistry, and biochemistry are used in worked examples, representative methods, and end-of-chapter problems Representative methods link theory with practice. An important feature of this text is the presentation of representative methods. These boxed features present typical analytical procedures in a format that encourages students to think about why the procedure is designed as it is Separate chapters on developing a standard method and quality assurance. Two chapters provide coverage of methods used in developing a standard method of analysis, and quality assurance. The chapter on developing a standard ethod includes topics such as opt rimental conditions using response surfaces, verifying the method through the blind analysis of standard samples and ruggedness testing, and collaborative testing using Youden's two-sample approach and ANOVA. The chapter on quality assurance covers quality control and internal and extern quality assessment, including the use of duplicate samples, blanks, spike recoveries, and control charts
Preface xiii Key Features of This Textbook Key features set this textbook apart from others currently available. • A stronger emphasis on the evaluation of data. Methods for characterizing chemical measurements, results, and errors (including the propagation of errors) are included. Both the binomial distribution and normal distribution are presented, and the idea of a confidence interval is developed. Statistical methods for evaluating data include the t-test (both for paired and unpaired data), the F-test, and the treatment of outliers. Detection limits also are discussed from a statistical perspective. Other statistical methods, such as ANOVA and ruggedness testing, are presented in later chapters. • Standardizations and calibrations are treated in a single chapter. Selecting the most appropriate calibration method is important and, for this reason, the methods of external standards, standard additions, and internal standards are gathered together in a single chapter. A discussion of curve-fitting, including the statistical basis for linear regression (with and without weighting) also is included in this chapter. • More attention to selecting and obtaining a representative sample. The design of a statistically based sampling plan and its implementation are discussed earlier, and in more detail than in other textbooks. Topics that are covered include how to obtain a representative sample, how much sample to collect, how many samples to collect, how to minimize the overall variance for an analytical method, tools for collecting samples, and sample preservation. • The importance of minimizing interferents is emphasized. Commonly used methods for separating interferents from analytes, such as distillation, masking, and solvent extraction, are gathered together in a single chapter. • Balanced coverage of analytical techniques. The six areas of analytical techniques—gravimetry, titrimetry, spectroscopy, electrochemistry, chromatography, and kinetics—receive roughly equivalent coverage, meeting the needs of instructors wishing to emphasize wet methods and those emphasizing instrumental methods. Related methods are gathered together in a single chapter encouraging students to see the similarities between methods, rather than focusing on their differences. • An emphasis on practical applications. Throughout the text applications from organic chemistry, inorganic chemistry, environmental chemistry, clinical chemistry, and biochemistry are used in worked examples, representative methods, and end-of-chapter problems. • Representative methods link theory with practice. An important feature of this text is the presentation of representative methods. These boxed features present typical analytical procedures in a format that encourages students to think about why the procedure is designed as it is. • Separate chapters on developing a standard method and quality assurance. Two chapters provide coverage of methods used in developing a standard method of analysis, and quality assurance. The chapter on developing a standard method includes topics such as optimizing experimental conditions using response surfaces, verifying the method through the blind analysis of standard samples and ruggedness testing, and collaborative testing using Youden’s two-sample approach and ANOVA. The chapter on quality assurance covers quality control and internal and external techniques for quality assessment, including the use of duplicate samples, blanks, spike recoveries, and control charts. 1400-Fm 9/9/99 7:38 AM Page xiii
XIV Problems adapted from the literature. Many of the in-chapter examples and end of-chapter problems are based on data from the analytical literature, providing students with practical examples of current research in analytical chemistry. An emphasis on critical thinking. Critical thinking is encouraged through problems in which students are asked to explain why certain steps in an analytical procedure are included, or to determine the effect of an expe error on the results of an analysis Suggested experiments from the Journal of Chemical Education. Rather than including a short collection of experiments emphasizing the analysis of standard unknowns, an annotated list of representative experiments from the Journal of Chemical Education is included at the conclusion of most chapters. These experiments may serve as stand alone experiments, or as starting points for individual or group projects. The role of equilibrium Chemistry in Analytical Chemistry Equilibrium chemistry often receives a significant emphasis in the introductory ana lytical chemistry course. While an important topic, its overemphasis can cause stu- dents to confuse analytical chemistry with equilibrium chemistry. Although atten- tion to solving equilibrium problems is important, it is equally important for stu- dents to recognize when such calculations are impractical, or when a simpler, more qualitative approach is all that is needed. For example, in discussing the gravimetric analysis of Ag* as AgCl, there is little point in calculating the equilibrium solubility of AgCl since the concentration of CI- at equilibrium is rarely known. It is impor tant, however, to qualitatively understand that a large excess of Ch- increases the sol ubility of AgCl due to the formation of soluble silver-chloro complexes. Balancing the presentation of a rigorous approach to solving equilibrium problems, this text also introduces the use of ladder diagrams as a means for providing a qualitative pic ture of a system at equilibrium. Students are encouraged to use the approach best suited to the probler Computer Software Many of the topics covered in analytical chemistry benefit from the availability of appropriate computer software. In preparing this text, however, I made a conscious decision to avoid a presentation tied to a single computer platform or software pack ge. Students and faculty are increasingly experienced in the use of computers, spreadsheets, and data analysis software; their use is, I think, best left to the per al choice of each student and instructor Organization The textbook's organization can be divided into four parts. Chapters 1-3 serve as an introduction, providing an overview of analytical chemistry( Chapter 1); a review of the basic tools of analytical chemistry, including significant figures, units, and stoi- biometry( Chapter 2); and an introduction to the terminology used by analytical chemists( Chapter 3). Familiarity with the material in these chapters is assumed throughout the remainder of the text. Chapters 4-7 cover a number of topics that are important in understanding how a particular analytical method works. Later chapters are mostly independent of the material in these chapters. Instructors may pick and choose from among the topics
• Problems adapted from the literature. Many of the in-chapter examples and endof-chapter problems are based on data from the analytical literature, providing students with practical examples of current research in analytical chemistry. • An emphasis on critical thinking. Critical thinking is encouraged through problems in which students are asked to explain why certain steps in an analytical procedure are included, or to determine the effect of an experimental error on the results of an analysis. • Suggested experiments from the Journal of Chemical Education. Rather than including a short collection of experiments emphasizing the analysis of standard unknowns, an annotated list of representative experiments from the Journal of Chemical Education is included at the conclusion of most chapters. These experiments may serve as stand alone experiments, or as starting points for individual or group projects. The Role of Equilibrium Chemistry in Analytical Chemistry Equilibrium chemistry often receives a significant emphasis in the introductory analytical chemistry course. While an important topic, its overemphasis can cause students to confuse analytical chemistry with equilibrium chemistry. Although attention to solving equilibrium problems is important, it is equally important for students to recognize when such calculations are impractical, or when a simpler, more qualitative approach is all that is needed. For example, in discussing the gravimetric analysis of Ag+ as AgCl, there is little point in calculating the equilibrium solubility of AgCl since the concentration of Cl– at equilibrium is rarely known. It is important, however, to qualitatively understand that a large excess of Cl– increases the solubility of AgCl due to the formation of soluble silver-chloro complexes. Balancing the presentation of a rigorous approach to solving equilibrium problems, this text also introduces the use of ladder diagrams as a means for providing a qualitative picture of a system at equilibrium. Students are encouraged to use the approach best suited to the problem at hand. Computer Software Many of the topics covered in analytical chemistry benefit from the availability of appropriate computer software. In preparing this text, however, I made a conscious decision to avoid a presentation tied to a single computer platform or software package. Students and faculty are increasingly experienced in the use of computers, spreadsheets, and data analysis software; their use is, I think, best left to the personal choice of each student and instructor. Organization The textbook’s organization can be divided into four parts. Chapters 1–3 serve as an introduction, providing an overview of analytical chemistry (Chapter 1); a review of the basic tools of analytical chemistry, including significant figures, units, and stoichiometry (Chapter 2); and an introduction to the terminology used by analytical chemists (Chapter 3). Familiarity with the material in these chapters is assumed throughout the remainder of the text. Chapters 4–7 cover a number of topics that are important in understanding how a particular analytical method works. Later chapters are mostly independent of the material in these chapters. Instructors may pick and choose from among the topics xiv Preface 1400-Fm 9/9/99 7:38 AM Page xiv
Preface of these chapters, as needed, to support individual course goals. The statistical analy- sis of data is covered in Chapter 4 at a level that is more complete than that found in other introductory analytical textbooks. Methods for calibrating equipment, stan dardizing methods, and linear regression are gathered together in Chapter 5.Chapter 6 provides an introduction to equilibrium chemistry, stressing both the rigorous solution to equilibrium problems, and the use of semi-quantitative approaches, such s ladder diagrams. The importance of collecting the right sample, and methods for separating analytes and interferents are covered in Chapter 7 Chapters 8-13 cover the major areas of analysis, including gravimetry Chapter 8),titrimetry( Chapter 9), spectroscopy(Chapter 10), electrochemistry ( Chapter 11), chromatography and electrophoresis( Chapter 12), and kinetic meth- ods( Chapter 13). Related techniques, such as acid-base titrimetry and redo titrimetry, or potentiometry and voltammetry, are gathered together in single chap- ters. Combining related techniques together encourages students to see the similar- ities between methods, rather than focusing on their differences. The first technique presented in each chapter is generally that which is most commonly covered in the introductory course. Finally, the textbook concludes with two chapters discussing the design and maintenance of analytical methods, two topics of importance to analytical chemists Chapter 14 considers the development of an analytical method, including its opti- mization,verification, and validation. Quality control and quality assessment are discussed in Chapter 15 Acknowledgments Before beginning an academic career I was, of course, a student. My interest in hemistry and teaching was nurtured by many fine teachers at Westtown Friends School, Knox College, and the University of North Carolina at Chapel Hill; their col- lective influence continues to bear fruit. In particular, I wish to recognize David MacInnes, Alan Hiebert, Robert Kooser and Richard Linton. I have been fortunate to work with many fine colleagues during my nearly 17 years of teaching undergraduate chemistry at Stockton State College and DePauw University. I am particularly grateful for the friendship and guidance provided by Jon Griffiths and Ed Paul during my four years at Stockton State College. At DePauw University, Jim George and Bryan Hanson have willingly shared their ideas about teaching, while patiently listening to mine Approximately 300 students have joined me in thinking and learning about ana- lytical chemistry; their questions and comments helped guide the development of this textbook. I realize that working without a formal textbook has been frustrating and awkward; all the more reason why I appreciate their effort and hard work. The following individuals reviewed portions of this textbook at various stages David ballantine Wendy Clevenger Northern Illinois University University of Tennessee-Chattanooga John E. bauer Cathy Cobb linois State University Augusta State University Ali Bazz Paul flowers University of Michigan-Dearborn University of North Carolina-Pembroke Steven d. brown Nancy gordon University of delaware University of Southern Maine
Preface xv of these chapters, as needed, to support individual course goals. The statistical analysis of data is covered in Chapter 4 at a level that is more complete than that found in other introductory analytical textbooks. Methods for calibrating equipment, standardizing methods, and linear regression are gathered together in Chapter 5. Chapter 6 provides an introduction to equilibrium chemistry, stressing both the rigorous solution to equilibrium problems, and the use of semi-quantitative approaches, such as ladder diagrams. The importance of collecting the right sample, and methods for separating analytes and interferents are covered in Chapter 7. Chapters 8–13 cover the major areas of analysis, including gravimetry (Chapter 8), titrimetry (Chapter 9), spectroscopy (Chapter 10), electrochemistry (Chapter 11), chromatography and electrophoresis (Chapter 12), and kinetic methods (Chapter 13). Related techniques, such as acid–base titrimetry and redox titrimetry, or potentiometry and voltammetry, are gathered together in single chapters. Combining related techniques together encourages students to see the similarities between methods, rather than focusing on their differences. The first technique presented in each chapter is generally that which is most commonly covered in the introductory course. Finally, the textbook concludes with two chapters discussing the design and maintenance of analytical methods, two topics of importance to analytical chemists. Chapter 14 considers the development of an analytical method, including its optimization, verification, and validation. Quality control and quality assessment are discussed in Chapter 15. Acknowledgments Before beginning an academic career I was, of course, a student. My interest in chemistry and teaching was nurtured by many fine teachers at Westtown Friends School, Knox College, and the University of North Carolina at Chapel Hill; their collective influence continues to bear fruit. In particular, I wish to recognize David MacInnes, Alan Hiebert, Robert Kooser, and Richard Linton. I have been fortunate to work with many fine colleagues during my nearly 17 years of teaching undergraduate chemistry at Stockton State College and DePauw University. I am particularly grateful for the friendship and guidance provided by Jon Griffiths and Ed Paul during my four years at Stockton State College. At DePauw University, Jim George and Bryan Hanson have willingly shared their ideas about teaching, while patiently listening to mine. Approximately 300 students have joined me in thinking and learning about analytical chemistry; their questions and comments helped guide the development of this textbook. I realize that working without a formal textbook has been frustrating and awkward; all the more reason why I appreciate their effort and hard work. The following individuals reviewed portions of this textbook at various stages during its development. David Ballantine Northern Illinois University John E. Bauer Illinois State University Ali Bazzi University of Michigan–Dearborn Steven D. Brown University of Delaware Wendy Clevenger University of Tennessee–Chattanooga Cathy Cobb Augusta State University Paul Flowers University of North Carolina–Pembroke Nancy Gordon University of Southern Maine 1400-Fm 9/9/99 7:38 AM Page xv
Preface Virginia M. Indivero Vincent reecho Swarthmore College West Virginia University Michael Janus Jeanette K Rice Nicholls State University Georgia Southern University Martin W. re Georgia Southern University Texas AeM University Richard S. mitchell Alexander Scheeline Arkansas State University University of Illinois George A Pearse, r James D. Stuart Le Moyne college University of Connecticut Thomas J. wenzel New Mexico State University Bates College David Redfield David zax Nw Nazarene University Cornell university I am particularly grateful for their detailed written comments and suggestions for of their interest and iae pt. Much of what is good in the final manuscript is the result improving the manuscr as. George Foy(York College of Pennsylvania), John McBride (Hofstra University), and David Karpovich( Saginaw Valley State University) checked the accuracy of problems in the textbook. Gary Kinsel (University of Texas at Arlington) reviewed the page proofs and provided additional suggestions This project began in the summer of 1992 with the support of a course develop- ment grant from DePauw University's Faculty Development Fund. Additional finan- cial support from DePauw Universitys Presidential Discretionary Fund also acknowledged. Portions of the first draft were written during a sabbatical leave in the Fall semester of the 1993/94 academic year. A Fisher Fellowship provided release time during the Fall 1995 semester to complete the manuscript's second draft Alltech and Associates(Deerfield, IL) graciously provided permission to use the chromatograms in Chapter 12; the assistance of Jim Anderson, Vice-President, and Julia Poncher, Publications Director, is greatly appreciated. Fred Soster and Marilyn Culler, both of DePauw University, provided assistance with some of the h The editorial staff at McGraw-Hill has helped guide a novice through the process of developing this text. I am particularly thankful for the encouragement and confidence shown by Jim Smith, Publisher for Chemistry, and Kent Peterson, Sponsoring Editor for Chemistry. Shirley Oberbroeckling, Developmental Editor for Chemistry, and Jayne Klein, Senior Project Manager, patiently answered my ques- tions and successfully guided me through the publishing process Finally, I would be remiss if I did not recognize the importance of my familys support and encouragement, particularly that of my parents. A very special thanks to my daughter, Devon, for gifts too numerous to detail. How to Contact the Author Writing this textbook has been an interesting(and exhausting) challenge. Despite my efforts, I am sure there are a few glitches, better examples, more interesting end of-chapter problems, and better ways to think about some of the topics. I welcome your comments, suggestions, and data for interesting problems, which may be addressed to me at DePauw University, 602 S College St, Greencastle, IN 46135, or electronically at harvey@depauw. edu
Virginia M. Indivero Swarthmore College Michael Janusa Nicholls State University J. David Jenkins Georgia Southern University Richard S. Mitchell Arkansas State University George A. Pearse, Jr. Le Moyne College Gary Rayson New Mexico State University David Redfield NW Nazarene University I am particularly grateful for their detailed written comments and suggestions for improving the manuscript. Much of what is good in the final manuscript is the result of their interest and ideas. George Foy (York College of Pennsylvania), John McBride (Hofstra University), and David Karpovich (Saginaw Valley State University) checked the accuracy of problems in the textbook. Gary Kinsel (University of Texas at Arlington) reviewed the page proofs and provided additional suggestions. This project began in the summer of 1992 with the support of a course development grant from DePauw University’s Faculty Development Fund. Additional financial support from DePauw University’s Presidential Discretionary Fund also is acknowledged. Portions of the first draft were written during a sabbatical leave in the Fall semester of the 1993/94 academic year. A Fisher Fellowship provided release time during the Fall 1995 semester to complete the manuscript’s second draft. Alltech and Associates (Deerfield, IL) graciously provided permission to use the chromatograms in Chapter 12; the assistance of Jim Anderson, Vice-President, and Julia Poncher, Publications Director, is greatly appreciated. Fred Soster and Marilyn Culler, both of DePauw University, provided assistance with some of the photographs. The editorial staff at McGraw-Hill has helped guide a novice through the process of developing this text. I am particularly thankful for the encouragement and confidence shown by Jim Smith, Publisher for Chemistry, and Kent Peterson, Sponsoring Editor for Chemistry. Shirley Oberbroeckling, Developmental Editor for Chemistry, and Jayne Klein, Senior Project Manager, patiently answered my questions and successfully guided me through the publishing process. Finally, I would be remiss if I did not recognize the importance of my family’s support and encouragement, particularly that of my parents. A very special thanks to my daughter, Devon, for gifts too numerous to detail. How to Contact the Author Writing this textbook has been an interesting (and exhausting) challenge. Despite my efforts, I am sure there are a few glitches, better examples, more interesting endof-chapter problems, and better ways to think about some of the topics. I welcome your comments, suggestions, and data for interesting problems, which may be addressed to me at DePauw University, 602 S. College St., Greencastle, IN 46135, or electronically at harvey@depauw.edu. xvi Preface Vincent Remcho West Virginia University Jeanette K. Rice Georgia Southern University Martin W. Rowe Texas A&M University Alexander Scheeline University of Illinois James D. Stuart University of Connecticut Thomas J. Wenzel Bates College David Zax Cornell University 1400-Fm 9/9/99 7:38 AM Page xvi