Modern Analytical Chemistry David Harvey DePauw University aw Boston Burr Ridge, IL Dubuque, IA Madison, WI New York San Francisco St Louis Bangkok Bogota Caracas Lisbon London Madrid Mexico City Milan New Delhi Seoul Singapore Sydney Taipei Toronto
Boston Burr Ridge, IL Dubuque, IA Madison, WI New York San Francisco St. Louis Bangkok Bogotá Caracas Lisbon London Madrid Mexico City Milan New Delhi Seoul Singapore Sydney Taipei Toronto CModern Analytical Chemistry hemistry David Harvey DePauw University 1400-Fm 9/9/99 7:37 AM Page i
Contents ntents Pr 2C.5 Conservation of electrons 2C.6 Using Conservation Principles in Chapter I Introduction 2D Basic Equipment and Instrumentation 25 2D. 1 Instrumentation for Measuring Mass 25 la What is Analytical Chemistry? 2 2D. 2 Equipment for Measuring Volume 26 1B The Analytical Perspective 5 2D.3 Equip Drying Ic Common Analytical Problems 8 2E Preparing Solutions 30 ID Key Terms 9 2E. I Preparing Stock Solutions 30 2E. 2 Preparing Solutions by Dilution 31 IF Problems 9 2F The Laboratory notebook 32 IG Suggested Readings 10 erms IH References 1 2I Problems 33 Chapter 2 2) Suggested Readings 34 Basic Tools of Analytical Chemistry ll 2K References 34 2A Numbers in Analytical Chemistry 12 Chapter 2A.1 Fundamental Units of measure 12 2A. 2 Significant Figures The Language of analytical Chemistry 35 2B Units for Expressing Concentration 15 3A Analysis, Determination, and Measurement 36 3B Techniques, Methods, Procedures, and 2B. 2 Normality 16 Protocols 36 2B.3 Molality 18 3c Classifying Analytical Techniques 37 2B.4 Weight, Volume, and Weight-to-Volume 3D Selecting an Analytical Method 38 Rat 3D.1 Accuracy 38 2B.5 Converting Between Concentration Units 18 3D.2 Precision 39 2B.6 p-Functions 19 3D.3 Sensitivity 39 2c Stoichiometric Calculations 20 3D.4 Selectivity 40 2C.1 Conservation of mass 22 3D.5 Robustness and Ruggedness 42 2C.2 Conservation of Charge 22 3D.6 Scale of Operation 42 2C. 3 Conservation of Protons 22 3D.7 Equipment, Time, and Cost 44 2C. 4 Conservation of electron pairs 23 3D. 8 Making the Final Choice 44
iii Contents Contents Preface xii Chapter 1 Introduction 1 1A What is Analytical Chemistry? 2 1B The Analytical Perspective 5 1C Common Analytical Problems 8 1D Key Terms 9 1E Summary 9 1F Problems 9 1G Suggested Readings 10 1H References 10 Chapter 2 Basic Tools of Analytical Chemistry 11 2A Numbers in Analytical Chemistry 12 2A.1 Fundamental Units of Measure 12 2A.2 Significant Figures 13 2B Units for Expressing Concentration 15 2B.1 Molarity and Formality 15 2B.2 Normality 16 2B.3 Molality 18 2B.4 Weight, Volume, and Weight-to-Volume Ratios 18 2B.5 Converting Between Concentration Units 18 2B.6 p-Functions 19 2C Stoichiometric Calculations 20 2C.1 Conservation of Mass 22 2C.2 Conservation of Charge 22 2C.3 Conservation of Protons 22 2C.4 Conservation of Electron Pairs 23 2C.5 Conservation of Electrons 23 2C.6 Using Conservation Principles in Stoichiometry Problems 23 2D Basic Equipment and Instrumentation 25 2D.1 Instrumentation for Measuring Mass 25 2D.2 Equipment for Measuring Volume 26 2D.3 Equipment for Drying Samples 29 2E Preparing Solutions 30 2E.1 Preparing Stock Solutions 30 2E.2 Preparing Solutions by Dilution 31 2F The Laboratory Notebook 32 2G Key Terms 32 2H Summary 33 2I Problems 33 2J Suggested Readings 34 2K References 34 Chapter 3 The Language of Analytical Chemistry 35 3A Analysis, Determination, and Measurement 36 3B Techniques, Methods, Procedures, and Protocols 36 3C Classifying Analytical Techniques 37 3D Selecting an Analytical Method 38 3D.1 Accuracy 38 3D.2 Precision 39 3D.3 Sensitivity 39 3D.4 Selectivity 40 3D.5 Robustness and Ruggedness 42 3D.6 Scale of Operation 42 3D.7 Equipment, Time, and Cost 44 3D.8 Making the Final Choice 44 1400-Fm 9/9/99 7:37 AM Page iii
Modern Analytical Chemistry 3E Developing the Procedure 45 4E. 4 Errors in Significance Testing 84 3E. I Compensating for Interferences 4 4F Statistical Methods for Normal distributions 85 BE2 Calibration and Standardization 47 paring X to 3E.3 Sampling 47 4F.2 Comparing s to o 87 3E.4 Validation 47 4F.3 Comparing Two Sample Variances 8 3F Protocols 48 4F.4 Comparing Two Sample Means 88 3G The Importance of Analytical Methodology 48 4F.5 Outline 3H Key Terms 50 4G Detection Limits 95 31 Summary 50 4H Key Terms 96 3 Problems 51 3K Suggested Readings 52 4] Suggested Experiments 9 3L Referene 4L Suggested Readings 102 Chapter 1 4M References 102 Evaluating Analytical Data 53 4A Characterizing Measurements and Results 54 Chapter 5 4A. 1 Measures of Central Tendency 54 Calibrations. Standardizations 4A. 2 Measures of Spread Ind blank Corrections 104 4B Characterizing Experimental Errors 57 5a Calibrating Signals 10. 5B Standardizing Methods 106 4B.2 Precision 62 5B. 1 Reagents Used as Standards 106 B3 Error and Uncertainty 64 5B. 2 Single-Point versus Multiple-Point 4c Propagation of Uncertainty 64 Standardizations 108 4C. 1 A Few Symbols 65 5B.3 External Standards 109 4C.2 Uncertainty When Adding or Subtracting 65 5B.4 Standard Additions 110 4C. 3 Uncertainty When Multiplying or 5B.5 Internal Standards 115 5C Linear Regression and Calibration Curves 117 4C.4 Uncertainty for Mixed Operations 66 5C.1 Linear Regression of Straight-Line Calibration 4C.5 Uncertainty for Other Mathematical Curves 118 Functions 67 C2 Unweighted Linear Regression with Errors 4C.6 Is Calculating Uncertainty Actually Useful? 68 4D The distribution of measurements and 5C.3 Weighted Linear Regression with Errors Results 70 4D.1 Populations and Samples 71 5C.4 Weighted Linear Regression with Errors 4D.2 Probability Distributions for Populations in Both x and y 127 4D.3 Confidence Intervals for Populations 75 C5 Curvilinear and multivariate 4D.4 Probability Distributions for Samples 77 4D.5 Confidence Intervals for Samples 80 5D Blank Corrections 128 4D.6 A Cautionary Statement 81 E Key Terms 130 4E Statistical Analysis of Data 82 ry130 4E. 1 Significance Testing 82 5G Suggested Experiments 130 4E.2 Constructing a Significance Test 83 5H Problems 131 4E.3 One-Tailed and Two-Tailed Significance ested Readings 133 I 5 References 134
iv Modern Analytical Chemistry 4E.4 Errors in Significance Testing 84 4F Statistical Methods for Normal Distributions 85 4F.1 Comparing – X to µ 85 4F.2 Comparing s2 to σ2 87 4F.3 Comparing Two Sample Variances 88 4F.4 Comparing Two Sample Means 88 4F.5 Outliers 93 4G Detection Limits 95 4H Key Terms 96 4I Summary 96 4J Suggested Experiments 97 4K Problems 98 4L Suggested Readings 102 4M References 102 Chapter 5 Calibrations, Standardizations, and Blank Corrections 104 5A Calibrating Signals 105 5B Standardizing Methods 106 5B.1 Reagents Used as Standards 106 5B.2 Single-Point versus Multiple-Point Standardizations 108 5B.3 External Standards 109 5B.4 Standard Additions 110 5B.5 Internal Standards 115 5C Linear Regression and Calibration Curves 117 5C.1 Linear Regression of Straight-Line Calibration Curves 118 5C.2 Unweighted Linear Regression with Errors in y 119 5C.3 Weighted Linear Regression with Errors in y 124 5C.4 Weighted Linear Regression with Errors in Both x and y 127 5C.5 Curvilinear and Multivariate Regression 127 5D Blank Corrections 128 5E Key Terms 130 5F Summary 130 5G Suggested Experiments 130 5H Problems 131 5I Suggested Readings 133 5J References 134 3E Developing the Procedure 45 3E.1 Compensating for Interferences 45 3E.2 Calibration and Standardization 47 3E.3 Sampling 47 3E.4 Validation 47 3F Protocols 48 3G The Importance of Analytical Methodology 48 3H Key Terms 50 3I Summary 50 3J Problems 51 3K Suggested Readings 52 3L References 52 Chapter 4 Evaluating Analytical Data 53 4A Characterizing Measurements and Results 54 4A.1 Measures of Central Tendency 54 4A.2 Measures of Spread 55 4B Characterizing Experimental Errors 57 4B.1 Accuracy 57 4B.2 Precision 62 4B.3 Error and Uncertainty 64 4C Propagation of Uncertainty 64 4C.1 A Few Symbols 65 4C.2 Uncertainty When Adding or Subtracting 65 4C.3 Uncertainty When Multiplying or Dividing 66 4C.4 Uncertainty for Mixed Operations 66 4C.5 Uncertainty for Other Mathematical Functions 67 4C.6 Is Calculating Uncertainty Actually Useful? 68 4D The Distribution of Measurements and Results 70 4D.1 Populations and Samples 71 4D.2 Probability Distributions for Populations 71 4D.3 Confidence Intervals for Populations 75 4D.4 Probability Distributions for Samples 77 4D.5 Confidence Intervals for Samples 80 4D.6 A Cautionary Statement 81 4E Statistical Analysis of Data 82 4E.1 Significance Testing 82 4E.2 Constructing a Significance Test 83 4E.3 One-Tailed and Two-Tailed Significance Tests 84 1400-Fm 9/9/99 7:37 AM Page iv
Contents ap 6 Chapter 7 Equilibrium Chemistry 135 obtaining and Preparing Samples fo nalySIs 79 6A Reversible reactions and Chemical quilibria 136 7A The Importance of Sampling 180 ling plan 1 Chemistry 136 7B. 1 Where to Sample the Target 6C Manipulating Equilibrium Constants 138 6D Equilibrium Constants for Chemica 7B.2 What Type of Sample to Collect 185 Reactions 139 B3 How Much Sample to Collect 187 6D. 1 Precipitation Reactions 139 7B.4 How Many Samples to Collect 191 6D.2 Acid-Base Reactions 140 7B.5 Minimizing the overall 6D.3 Complexation Reactions 144 7C Implementing the Sampling Plan 193 D 4 Oxidation-Reduction Reactions 14 7C.1 Solutions 193 E Le Chatelier's Principle 148 7C.2 Gases 195 6F Ladder Diagrams 150 7C.3 Solids 196 6F.1 Ladder Diagrams for Acid-Base Equilibria 150 7D Separating the Analyte from 6F.2 Ladder Diagrams for Complexation nterferents 201 Equilibria 153 E General Theory of separation 6F. 3 Ladder Diagrams for Oxidation-Reduction 7F Classifying Separation Techniques 205 6G Solving Equilibrium Problems 156 7F.1 Separations Based on Size 205 6G.1 A Simple Problem: Solubility of Pb(IO3)2in 7F.2 Separations Based on Mass or Density 206 Water 156 7F.3 Separations Based on Complexation 6G.2 A More Complex Problem: The Common lon 6G.3 Systematic Approach to Solving Equilibrium of State 209 Problems 159 7F.5 Separations Based on a Partitioning Betwe 6G.4 pH of a Monoprotic Weak Acid 160 Phases 211 6G.5 pH of a Polyprotic Acid or Base 7G Liquid-Liquid Extractions 215 6G.6 Effect of Complexation on Solubilit 7G.1 Partition Coefficients and Distribution 6H Buffer Solutions 167 Ratio 6H. 1 Systematic Solution to Buffer G2 Liquid-Liquid Extraction with No Secondary Problems 168 Reactions 216 6H.2 Representing Buffer Solutions with 7G.3 Liquid-Liquid Extractions Involving Ladder Diagrams 170 Acid-Base Equilibria 219 61 Activity Effects 171 7G.4 Liquid-Liquid Extractions Involving Metal 6] Two Final Thoughts About Equilibrium Chelators 221 Chemistry 175 7H Separation versus Preconcentration 223 6K Key Terms 17 71 Key Terms 224 6L Summary 175 6M Suggested Experiments 176 Suggested Experiments 225 6n Problems 176 Problems 226 60 Suggested Readings 178 7M Suggested Readings 230 6P References 178 7n References 231
Contents v Chapter 7 Obtaining and Preparing Samples for Analysis 179 7A The Importance of Sampling 180 7B Designing a Sampling Plan 182 7B.1 Where to Sample the Target Population 182 7B.2 What Type of Sample to Collect 185 7B.3 How Much Sample to Collect 187 7B.4 How Many Samples to Collect 191 7B.5 Minimizing the Overall Variance 192 7C Implementing the Sampling Plan 193 7C.1 Solutions 193 7C.2 Gases 195 7C.3 Solids 196 7D Separating the Analyte from Interferents 201 7E General Theory of Separation Efficiency 202 7F Classifying Separation Techniques 205 7F.1 Separations Based on Size 205 7F.2 Separations Based on Mass or Density 206 7F.3 Separations Based on Complexation Reactions (Masking) 207 7F.4 Separations Based on a Change of State 209 7F.5 Separations Based on a Partitioning Between Phases 211 7G Liquid–Liquid Extractions 215 7G.1 Partition Coefficients and Distribution Ratios 216 7G.2 Liquid–Liquid Extraction with No Secondary Reactions 216 7G.3 Liquid–Liquid Extractions Involving Acid–Base Equilibria 219 7G.4 Liquid–Liquid Extractions Involving Metal Chelators 221 7H Separation versus Preconcentration 223 7I Key Terms 224 7J Summary 224 7K Suggested Experiments 225 7L Problems 226 7M Suggested Readings 230 7N References 231 Chapter 6 Equilibrium Chemistry 135 6A Reversible Reactions and Chemical Equilibria 136 6B Thermodynamics and Equilibrium Chemistry 136 6C Manipulating Equilibrium Constants 138 6D Equilibrium Constants for Chemical Reactions 139 6D.1 Precipitation Reactions 139 6D.2 Acid–Base Reactions 140 6D.3 Complexation Reactions 144 6D.4 Oxidation–Reduction Reactions 145 6E Le Châtelier’s Principle 148 6F Ladder Diagrams 150 6F.1 Ladder Diagrams for Acid–Base Equilibria 150 6F.2 Ladder Diagrams for Complexation Equilibria 153 6F.3 Ladder Diagrams for Oxidation–Reduction Equilibria 155 6G Solving Equilibrium Problems 156 6G.1 A Simple Problem: Solubility of Pb(IO3)2 in Water 156 6G.2 A More Complex Problem: The Common Ion Effect 157 6G.3 Systematic Approach to Solving Equilibrium Problems 159 6G.4 pH of a Monoprotic Weak Acid 160 6G.5 pH of a Polyprotic Acid or Base 163 6G.6 Effect of Complexation on Solubility 165 6H Buffer Solutions 167 6H.1 Systematic Solution to Buffer Problems 168 6H.2 Representing Buffer Solutions with Ladder Diagrams 170 6I Activity Effects 171 6J Two Final Thoughts About Equilibrium Chemistry 175 6K Key Terms 175 6L Summary 175 6M Suggested Experiments 176 6N Problems 176 6O Suggested Readings 178 6P References 178 1400-Fm 9/9/99 7:38 AM Page v
Modern Analytical Chemistry Chapter 8 9B.7 Characterization Applications 309 9B.8 Evaluation of Acid-Base Titrimetry 31 Gravimetric Methods of analysis 232 9c Titrations Based on Complexation Reactions 314 8A Overview of Gravimetry 233 9C.1 Chemistry and Properties of EDTA 315 8A.1 Using Mass as a Signal 233 9C.2 Complexometric EDTA Titration Curves 317 8A.2 Types of Gravimetric Methods 234 9C.3 Selecting and Evaluating the End Point 322 8A.3 Conservation of mass 23 9C.4 Representative Method 324 8A.4 Why Gravimetry Is Important 235 9C.5 Quantitative Applications 327 8B Precipitation Gravimetry 235 9C.6 Evaluation of Complexation Titrimetry 331 8B. 1 Theory and Practice 235 9D Titrations Based on redox Reactions 331 8B.2 Quantitative Applications 247 9D.1 Redox Titration Curves 332 9D.2 Selecting and Evaluating the End Point 337 8B. 4 Evaluating Precipitation Gravimetry 254 Representative Method 340 8C Volatilization Gravimetry 255 9D. 4 Quantitative Applications 341 8C.1 Theory and Practice 255 9D.5 Evaluation of Redox Titrimetry 350 8C.2 Quantitative Applications 259 9E Precipitation Titrations 350 8C.3 Evaluating Volatilization Gravimetry 262 9E.1 Titration Curves 350 8D Particulate Gravimetry 262 9E.2 Selecting and Evaluating the End Point 354 8D.1 Theory and Practice 263 9E.3 Quantitative Applications 354 8D.2 Quantitative Applications 264 9E.4 Evaluation of Precipitation Titrimetry 357 8D.3 Evaluating Precipitation Gravimetry 265 9F Key Terms 357 8E Key terms Summary 357 8F Summary 266 9H Suggested Experiments 358 8G Suggested Experiments 26 9I Problems 360 8H Problems 267 9] Suggested Readings 366 9K References 367 8 References 272 Chapter Io Chapter 9 Spectroscopic Methods Titrimetric Methods of analysis 273 of analysis368 9A Overview of Titrimetry 274 10A.1 What Is Electromagnetic Radiation 369 9A. 1 Equivalence Points and End Points 274 9A.2 Volume as a Signal 274 10A.2 Measuring Photons as a Signal 372 9A.3 Titration Curves 275 OB Basic Components of Spectroscopic Instrumentation 374 9A.4 The buret 277 10B. 1 Sources of Energy 375 b Titrations Based on acid-Base Reactions 278 10B. 2 Wavelength Selection 376 9B.1 Acid-Base Titration Curves 279 10B. 3 Detectors 379 9B.2 Selecting and Evaluating the 10B.4 Signal Processors 38 End point 287 10C Spectroscopy Based on Absorption 380 9B.3 Titrations in Nonaqueous Solvents 295 9B.4 Representative Method 296 10C.1 Absorbance of Electromagnetic Radiation 380 10C. 2 Transmittance and Absorbance 384 9B.5 Quantitative Applications 298 10C. 3 Absorbance and Concentration: Beers 9B.6 Qualitative Applications 308 Law 385
vi Modern Analytical Chemistry Chapter 8 Gravimetric Methods of Analysis 232 8A Overview of Gravimetry 233 8A.1 Using Mass as a Signal 233 8A.2 Types of Gravimetric Methods 234 8A.3 Conservation of Mass 234 8A.4 Why Gravimetry Is Important 235 8B Precipitation Gravimetry 235 8B.1 Theory and Practice 235 8B.2 Quantitative Applications 247 8B.3 Qualitative Applications 254 8B.4 Evaluating Precipitation Gravimetry 254 8C Volatilization Gravimetry 255 8C.1 Theory and Practice 255 8C.2 Quantitative Applications 259 8C.3 Evaluating Volatilization Gravimetry 262 8D Particulate Gravimetry 262 8D.1 Theory and Practice 263 8D.2 Quantitative Applications 264 8D.3 Evaluating Precipitation Gravimetry 265 8E Key Terms 265 8F Summary 266 8G Suggested Experiments 266 8H Problems 267 8I Suggested Readings 271 8J References 272 Chapter 9 Titrimetric Methods of Analysis 273 9A Overview of Titrimetry 274 9A.1 Equivalence Points and End Points 274 9A.2 Volume as a Signal 274 9A.3 Titration Curves 275 9A.4 The Buret 277 9B Titrations Based on Acid–Base Reactions 278 9B.1 Acid–Base Titration Curves 279 9B.2 Selecting and Evaluating the End Point 287 9B.3 Titrations in Nonaqueous Solvents 295 9B.4 Representative Method 296 9B.5 Quantitative Applications 298 9B.6 Qualitative Applications 308 9B.7 Characterization Applications 309 9B.8 Evaluation of Acid–Base Titrimetry 311 9C Titrations Based on Complexation Reactions 314 9C.1 Chemistry and Properties of EDTA 315 9C.2 Complexometric EDTA Titration Curves 317 9C.3 Selecting and Evaluating the End Point 322 9C.4 Representative Method 324 9C.5 Quantitative Applications 327 9C.6 Evaluation of Complexation Titrimetry 331 9D Titrations Based on Redox Reactions 331 9D.1 Redox Titration Curves 332 9D.2 Selecting and Evaluating the End Point 337 9D.3 Representative Method 340 9D.4 Quantitative Applications 341 9D.5 Evaluation of Redox Titrimetry 350 9E Precipitation Titrations 350 9E.1 Titration Curves 350 9E.2 Selecting and Evaluating the End Point 354 9E.3 Quantitative Applications 354 9E.4 Evaluation of Precipitation Titrimetry 357 9F Key Terms 357 9G Summary 357 9H Suggested Experiments 358 9I Problems 360 9J Suggested Readings 366 9K References 367 Chapter 10 Spectroscopic Methods of Analysis 368 10A Overview of Spectroscopy 369 10A.1 What Is Electromagnetic Radiation 369 10A.2 Measuring Photons as a Signal 372 10B Basic Components of Spectroscopic Instrumentation 374 10B.1 Sources of Energy 375 10B.2 Wavelength Selection 376 10B.3 Detectors 379 10B.4 Signal Processors 380 10C Spectroscopy Based on Absorption 380 10C.1 Absorbance of Electromagnetic Radiation 380 10C.2 Transmittance and Absorbance 384 10C.3 Absorbance and Concentration: Beer’s Law 385 1400-Fm 9/9/99 7:38 AM Page vi
10C.4 Beer's Law and Multicomponent 11B Potentiometric Methods of Analysis 465 Samples 386 11B.1 Potentiometric measurements 466 10C.5 Limitations to Beers Law 386 11B.2 Reference Electrodes 471 IOD Ultraviolet-Visible and Infrared 11B. 3 Metallic Indicator Electrodes 473 Spectrophotometry 388 11B.4 Membrane electrodes 475 10D.1 Instrumentation 388 11B.5 Quantitative Applications 485 10D.2 Quantitative Applications 394 10D. 3 Qualitative Applications 402 11B.6 Evaluation 494 lIc Coulometric Methods of Analys 10D.4 Characterization Applications 403 11C.1 Controlled-Potential Coulometry 49 10D.5 Evaluation 409 11C.2 Controlled-Current Coulometry 499 10E Atomic Absorption Spectroscopy 412 11C.3 Quantitative Applications 501 10E 1 Instrumentation 412 1IC. 4 Characterization Applications 506 0E. 2 Quantitative Applications 415 11C.5 Evaluation 507 Evaluation 422 lld Voltammetric Methods of Analysis 508 10F Spectroscopy Based on Emission 423 llD.1 Voltammetric Measurements 509 10G Molecular photoluminescent llD. 2 Current in Voltammetry 510 Spectroscopy 423 11D.3 Shape of Voltammograms 513 OG.1 Molecular fluorescence and rescence Spectra 424 11D. 4 Quantitative and Qualitative Aspect of Voltammetry 514 10G. 2 Instrumentation 427 11D.5 Voltammetric Techniques 515 10G.3 Quantitative Applications Using Molecular 11D.6 Quantitative Applications 520 10G. 4 Evaluation 432 11D.7 Characterization Applications 52 11D. 8 Evaluation 531 10H Atomic Emission Spectroscopy 434 10H. 1 Atomic Emission Spectra 434 lie Key Terms 532 0H.2 Equipment 435 IF Summary 532 0H.3 Quantitative Applications 437 lIG Suggested Experiments 533 1OH.4 Evaluatic IIH Problems 535 101 Spectroscopy Based on Scattering 441 llI Suggested Readings 540 101.1 Origin of Scattering 441 11 References 541 101.2 Turbidimetry and Nephelometry 441 Chapter 12 10) Key Terms 446 Chromatographic and Electrophoretic 10L Suggested Experiments 447 Methods 543 10M Problems 450 12A Overview of Analytical Separations 544 10n Suggested Readings 458 12A.1 The Problem with Simple ferences 459 Separations 544 12A. 2 A Better Way to Separate Mixtures 544 Chapter ll Electrochemical Methods of Analysis 461 12B General Theory of Column Chromatography 547 lla Classification of electrochemical methods 462 12B. 1 Chromatographic Resolution 549 11A.1 Interfacial Electrochemical Methods 462 12B.2 Capacity Factor 550 11A.2 Controlling and Measuring Current and 2B.3 Column Selectivity Potential 462 2B. 4 Column efficien
Contents vii 11B Potentiometric Methods of Analysis 465 11B.1 Potentiometric Measurements 466 11B.2 Reference Electrodes 471 11B.3 Metallic Indicator Electrodes 473 11B.4 Membrane Electrodes 475 11B.5 Quantitative Applications 485 11B.6 Evaluation 494 11C Coulometric Methods of Analysis 496 11C.1 Controlled-Potential Coulometry 497 11C.2 Controlled-Current Coulometry 499 11C.3 Quantitative Applications 501 11C.4 Characterization Applications 506 11C.5 Evaluation 507 11D Voltammetric Methods of Analysis 508 11D.1 Voltammetric Measurements 509 11D.2 Current in Voltammetry 510 11D.3 Shape of Voltammograms 513 11D.4 Quantitative and Qualitative Aspects of Voltammetry 514 11D.5 Voltammetric Techniques 515 11D.6 Quantitative Applications 520 11D.7 Characterization Applications 527 11D.8 Evaluation 531 11E Key Terms 532 11F Summary 532 11G Suggested Experiments 533 11H Problems 535 11I Suggested Readings 540 11J References 541 Chapter 12 Chromatographic and Electrophoretic Methods 543 12A Overview of Analytical Separations 544 12A.1 The Problem with Simple Separations 544 12A.2 A Better Way to Separate Mixtures 544 12A.3 Classifying Analytical Separations 546 12B General Theory of Column Chromatography 547 12B.1 Chromatographic Resolution 549 12B.2 Capacity Factor 550 12B.3 Column Selectivity 552 12B.4 Column Efficiency 552 10C.4 Beer’s Law and Multicomponent Samples 386 10C.5 Limitations to Beer’s Law 386 10D Ultraviolet-Visible and Infrared Spectrophotometry 388 10D.1 Instrumentation 388 10D.2 Quantitative Applications 394 10D.3 Qualitative Applications 402 10D.4 Characterization Applications 403 10D.5 Evaluation 409 10E Atomic Absorption Spectroscopy 412 10E.1 Instrumentation 412 10E.2 Quantitative Applications 415 10E.3 Evaluation 422 10F Spectroscopy Based on Emission 423 10G Molecular Photoluminescence Spectroscopy 423 10G.1 Molecular Fluorescence and Phosphorescence Spectra 424 10G.2 Instrumentation 427 10G.3 Quantitative Applications Using Molecular Luminescence 429 10G.4 Evaluation 432 10H Atomic Emission Spectroscopy 434 10H.1 Atomic Emission Spectra 434 10H.2 Equipment 435 10H.3 Quantitative Applications 437 10H.4 Evaluation 440 10I Spectroscopy Based on Scattering 441 10I.1 Origin of Scattering 441 10I.2 Turbidimetry and Nephelometry 441 10J Key Terms 446 10K Summary 446 10L Suggested Experiments 447 10M Problems 450 10N Suggested Readings 458 10O References 459 Chapter 11 Electrochemical Methods of Analysis 461 11A Classification of Electrochemical Methods 462 11A.1 Interfacial Electrochemical Methods 462 11A.2 Controlling and Measuring Current and Potential 462 1400-Fm 9/9/99 7:38 AM Page vii
Modern Analytical Chemistry 2B.5 Peak Capacity 554 120 Suggested Readings 620 2B.6 Nonideal Behavior 555 12P References 620 12C Optimizing Chromatographic Separations 556 12C.1 Using the Capacity Factor to Optimize Chapter 13 Resol 12C.2 Using Column Selectivity to Optimize Kinetic Methods of Analysis 622 Resolution 558 13A Methods based on chemical kinetics 623 2C.3 Using Column Efficiency to Optimize 13A.1 Theory and Practice 624 Resolution 559 13A.2 Instrumentation 634 12D Gas Chromatography 563 13A.3 Quantitative Applications 636 2D.1 Mobile phase 563 13A.4 Characterization Applications 638 12D.2 Chromatographic Columns 564 13A.5 Evaluation of Chemical Kinetic 2D.3 Stationary Phases 565 Methods 639 12D.4 Sample Introduction 567 13B Radiochemical Methods of Analysis 642 3B. 1 Theory and Practice 643 12D.6 Detectors for Gas Chromatography 569 3B. 2 Instrumentation 64 12D.7 Quantitative Applications 571 13B.3 Quantitative Applications 644 2D.8 Qualitative Applications 575 13B.4 Characterization Applications 647 12D.9 Representative Method 576 648 2D.10 Evaluatic 13C Flow Injection Analysis 649 2E High-Performance Liquid 13C. 1 Theory and Practice 649 cromatography 578 13C.2 Instrumentation 651 12E. 1 HPLC Columns 578 13C.3 Quantitative Applications 655 12E.2 Stationary Ph 579 13C.4 Evaluation 658 12E. 3 Mobile Phases 580 13D Key Terms 658 2E. 4 HPLC Plumbing 583 13E 659 12E.5 Sample Introduction 584 13F Suggested Experiments 659 12E. 6 Detectors for HPlc 584 13G Problems 661 2E.7 Quantitative Applications 58( 13H Suggested Readings 664 12E.8 Representative Method 588 13I References 665 12E. 9 Evaluation 589 12F Liquid-Solid Adsorption Chromatography 590 Chapter I 4 12G Ion-Exchange Chromatography 590 H Size-Exclusion Chromatography 593 Developing a Standard Method 666 121 Supercritical Fluid Chromatography 596 14A Optimizing the Experimental Procedure 667 12] Electrophoresis 597 14A.1R 12].1 Theory of Capillary Electrophoresis 598 14A.2 Searching Algorithms for Response 2J.2 Instrumentation 601 Surfaces 668 J3 Capillary Electrophoresis Methods 604 14A. 3 Mathematical Models of Response 12J.4 Representative Method 607 2J.5 Evaluation 609 14B Verifying the Method 683 12K Key Terms 609 14B. 1 Single-Operator Characteristics 683 12L Summary 610 14B. 2 Blind Analysis of Standard Samples 683 I2M Suggested Experiments 610 14B.3R 12n Problems 615 14B. 4 Equivalency Testing 687
12B.5 Peak Capacity 554 12B.6 Nonideal Behavior 555 12C Optimizing Chromatographic Separations 556 12C.1 Using the Capacity Factor to Optimize Resolution 556 12C.2 Using Column Selectivity to Optimize Resolution 558 12C.3 Using Column Efficiency to Optimize Resolution 559 12D Gas Chromatography 563 12D.1 Mobile Phase 563 12D.2 Chromatographic Columns 564 12D.3 Stationary Phases 565 12D.4 Sample Introduction 567 12D.5 Temperature Control 568 12D.6 Detectors for Gas Chromatography 569 12D.7 Quantitative Applications 571 12D.8 Qualitative Applications 575 12D.9 Representative Method 576 12D.10 Evaluation 577 12E High-Performance Liquid Chromatography 578 12E.1 HPLC Columns 578 12E.2 Stationary Phases 579 12E.3 Mobile Phases 580 12E.4 HPLC Plumbing 583 12E.5 Sample Introduction 584 12E.6 Detectors for HPLC 584 12E.7 Quantitative Applications 586 12E.8 Representative Method 588 12E.9 Evaluation 589 12F Liquid–Solid Adsorption Chromatography 590 12G Ion-Exchange Chromatography 590 12H Size-Exclusion Chromatography 593 12I Supercritical Fluid Chromatography 596 12J Electrophoresis 597 12J.1 Theory of Capillary Electrophoresis 598 12J.2 Instrumentation 601 12J.3 Capillary Electrophoresis Methods 604 12J.4 Representative Method 607 12J.5 Evaluation 609 12K Key Terms 609 12L Summary 610 12M Suggested Experiments 610 12N Problems 615 viii Modern Analytical Chemistry 12O Suggested Readings 620 12P References 620 Chapter 13 Kinetic Methods of Analysis 622 13A Methods Based on Chemical Kinetics 623 13A.1 Theory and Practice 624 13A.2 Instrumentation 634 13A.3 Quantitative Applications 636 13A.4 Characterization Applications 638 13A.5 Evaluation of Chemical Kinetic Methods 639 13B Radiochemical Methods of Analysis 642 13B.1 Theory and Practice 643 13B.2 Instrumentation 643 13B.3 Quantitative Applications 644 13B.4 Characterization Applications 647 13B.5 Evaluation 648 13C Flow Injection Analysis 649 13C.1 Theory and Practice 649 13C.2 Instrumentation 651 13C.3 Quantitative Applications 655 13C.4 Evaluation 658 13D Key Terms 658 13E Summary 659 13F Suggested Experiments 659 13G Problems 661 13H Suggested Readings 664 13I References 665 Chapter 14 Developing a Standard Method 666 14A Optimizing the Experimental Procedure 667 14A.1 Response Surfaces 667 14A.2 Searching Algorithms for Response Surfaces 668 14A.3 Mathematical Models of Response Surfaces 674 14B Verifying the Method 683 14B.1 Single-Operator Characteristics 683 14B.2 Blind Analysis of Standard Samples 683 14B.3 Ruggedness Testing 684 14B.4 Equivalency Testing 687 1400-Fm 9/9/99 7:38 AM Page viii
14c Validating the Method as a Standard 15d Key Terms 721 Method 687 15E Summary 722 14C.1 Two-Sample Collaborative Testing 68 15F Suggested Experiments 722 14C.2 Collaborative Testing and Analysis of 15G Problems 722 Variance 693 15H Suggested Readings 724 14C. 3 What Is a Reasonable Result for a 15I References 724 collaborative Study? 698 14D Key Terms 699 14E St Appendixes 14F Suggested Experiments 699 Appendix IA Single-Sided Normal Distribution 725 14G Problems 700 Appendix IB I-Table 726 Appendix IC F-Table 727 14H Suggested Readings 704 Appendix ID Critical Values for Q-Test 728 14I References 704 Appendix 1E Random Number Table 728 Appendix 2 Recommended Reagents for Preparing Primary Chapter 15 Standards 729 Quality Assurance 705 Appendix 3B Acid Dissociation Constants 732 Appendix 3C Metal-Ligand Formation Constants 739 15A Quality Control 706 Appendix 3D Standard Reduction Potentials 743 15B Quality Assessment 708 Appendix 3E Selected Polarographic Half-Wave Potentials 747 15B. 1 Internal Methods of Qualit Appendix 4 Balancing Redox Reactions 748 Assessment 708 Appendix 5 Review of Chemical Kinetics 750 15B.2 External Methods of Quality ppendix 6 Assessment 711 Appendix 7 Answers to Selected Problems 762 15C Evaluating Quality Assurance Data 712 5C.1 Prescriptive Approach 712 Glossary 769 Index 781 15C.2 Performance-Based Approach 714
Contents ix 15D Key Terms 721 15E Summary 722 15F Suggested Experiments 722 15G Problems 722 15H Suggested Readings 724 15I References 724 Appendixes Appendix 1A Single-Sided Normal Distribution 725 Appendix 1B t-Table 726 Appendix 1C F-Table 727 Appendix 1D Critical Values for Q-Test 728 Appendix 1E Random Number Table 728 Appendix 2 Recommended Reagents for Preparing Primary Standards 729 Appendix 3A Solubility Products 731 Appendix 3B Acid Dissociation Constants 732 Appendix 3C Metal–Ligand Formation Constants 739 Appendix 3D Standard Reduction Potentials 743 Appendix 3E Selected Polarographic Half-Wave Potentials 747 Appendix 4 Balancing Redox Reactions 748 Appendix 5 Review of Chemical Kinetics 750 Appendix 6 Countercurrent Separations 755 Appendix 7 Answers to Selected Problems 762 Glossary 769 Index 781 14C Validating the Method as a Standard Method 687 14C.1 Two-Sample Collaborative Testing 688 14C.2 Collaborative Testing and Analysis of Variance 693 14C.3 What Is a Reasonable Result for a Collaborative Study? 698 14D Key Terms 699 14E Summary 699 14F Suggested Experiments 699 14G Problems 700 14H Suggested Readings 704 14I References 704 Chapter 15 Quality Assurance 705 15A Quality Control 706 15B Quality Assessment 708 15B.1 Internal Methods of Quality Assessment 708 15B.2 External Methods of Quality Assessment 711 15C Evaluating Quality Assurance Data 712 15C.1 Prescriptive Approach 712 15C.2 Performance-Based Approach 714 1400-Fm 9/9/99 7:38 AM Page ix
A Guide to Using This Text .. in Chapter Representative Methods Annotated methods of typical analytical procedures link theory with when the isolated solid is Do practice. The format encourages students to think about the design of the procedure and why it works. precipitating MgNH, PO, 6H,O and isolating Ms P, O, provides a Margin Notes Margin Determination of Mga in Water and t note to colorplates located t the middle of the book fltering, the precipitate is converted to Maj P O,and weighed r case, the calibration curve provides for relating Sung to EXAMLE5.3 Celar plah Ithow时 =(0396pb-)xCs+0.03 出的,贴钟m of Pb* in the sample of bood, we replace 1.33 Ppb nation results from uncertainty in measuring the signal for 把 e many peace Nbzedgben Examples of Typical Problems Each example problem includes a eireann detailed solution that helps students in complication of matching the matrix of the standards to that of the sample applying the chapter's material to practical problems. whc1 da secoed identical aliquot of sam中 Bold-faced Key Terms with Margin Definitions Key words appear in boldface when they are introduced within the text The term and its definition appear in the margin for quick review by the student. All key words are also defined in the glossar
x Modern Analytical Chemistry A Guide to Using This Text . . . in Chapter Representative Methods Annotated methods of typical analytical procedures link theory with practice. The format encourages students to think about the design of the procedure and why it works. 246 Modern Analytical Chemistry Representative Methods An additional problem is encountered when the isolated solid is nonstoichiometric. For example, precipitating Mn2+ as Mn(OH)2, followed by heating to produce the oxide, frequently produces a solid with a stoichiometry of MnOx, where x varies between 1 and 2. In this case the nonstoichiometric product results from the formation of a mixture of several oxides that differ in the oxidation state of manganese. Other nonstoichiometric compounds form as a result of lattice defects in the crystal structure.6 Representative Method The best way to appreciate the importance of the theoretical and practical details discussed in the previous section is to carefully examine the procedure for a typical precipitation gravimetric method. Although each method has its own unique considerations, the determination of Mg2+ in water and wastewater by precipitating MgNH4PO4 ⋅ 6H2O and isolating Mg2P2O7 provides an instructive example of a typical procedure. Method 8.1 Determination of Mg2+ in Water and Wastewater7 Description of Method. Magnesium is precipitated as MgNH4PO4 ⋅ 6H2O using (NH4)2HPO4 as the precipitant. The precipitate’s solubility in neutral solutions (0.0065 g/100 mL in pure water at 10 °C) is relatively high, but it is much less soluble in the presence of dilute ammonia (0.0003 g/100 mL in 0.6 M NH3). The precipitant is not very selective, so a preliminary separation of Mg2+ from potential interferents is necessary. Calcium, which is the most significant interferent, is usually removed by its prior precipitation as the oxalate. The presence of excess ammonium salts from the precipitant or the addition of too much ammonia can lead to the formation of Mg(NH4)4(PO4)2, which is subsequently isolated as Mg(PO3)2 after drying. The precipitate is isolated by filtration using a rinse solution of dilute ammonia. After filtering, the precipitate is converted to Mg2P2O7 and weighed. Procedure. Transfer a sample containing no more than 60 mg of Mg2+ into a 600-mL beaker. Add 2–3 drops of methyl red indicator, and, if necessary, adjust the volume to 150 mL. Acidify the solution with 6 M HCl, and add 10 mL of 30% w/v (NH4)2HPO4. After cooling, add concentrated NH3 dropwise, and while constantly stirring, until the methyl red indicator turns yellow (pH > 6.3). After stirring for 5 min, add 5 mL of concentrated NH3, and continue stirring for an additional 10 min. Allow the resulting solution and precipitate to stand overnight. Isolate the precipitate by filtration, rinsing with 5% v/v NH3. Dissolve the precipitate in 50 mL of 10% v/v HCl, and precipitate a second time following the same procedure. After filtering, carefully remove the filter paper by charring. Heat the precipitate at 500 °C until the residue is white, and then bring the precipitate to constant weight at 1100 °C. Questions 1. Why does the procedure call for a sample containing no more than 60 mg of q y There is a serious limitation, however, to an external standardization. The relationship between Sstand and CS in equation 5.3 is determined when the analyte is present in the external standard’s matrix. In using an external standardization, we assume that any difference between the matrix of the standards and the sample’s matrix has no effect on the value of k. A proportional determinate error is introduced when differences between the two matrices cannot be ignored. This is shown in Figure 5.4, where the relationship between the signal and the amount of analyte is shown for both the sample’s matrix and the standard’s matrix. In this example, using a normal calibration curve results in a negative determinate error. When matrix problems are expected, an effort is made to match the matrix of the standards to that of the sample. This is known as matrix matching. When the sample’s matrix is unknown, the matrix effect must be shown to be negligible, or an alternative method of standardization must be used. Both approaches are discussed in the following sections. 5B.4 Standard Additions The complication of matching the matrix of the standards to that of the sample can be avoided by conducting the standardization in the sample. This is known as the method of standard additions. The simplest version of a standard addition is shown in Figure 5.5. A volume, Vo, of sample is diluted to a final volume, Vf, and the signal, Ssamp is measured. A second identical aliquot of sample is matrix matching Adjusting the matrix of an external standard so that it is the same as the matrix of the samples to be analyzed. method of standard additions A standardization in which aliquots of a standard solution are added to the sample. Examples of Typical Problems Each example problem includes a detailed solution that helps students in applying the chapter’s material to practical problems. Margin Notes Margin notes direct students to colorplates located toward the middle of the book Bold-faced Key Terms with Margin Definitions Key words appear in boldface when they are introduced within the text. The term and its definition appear in the margin for quick review by the student. All key words are also defined in the glossary. 110 Modern Analytical Chemistry either case, the calibration curve provides a means for relating Ssamp to the analyte’s concentration. EXAMPLE 5.3 A second spectrophotometric method for the quantitative determination of Pb2+ levels in blood gives a linear normal calibration curve for which Sstand = (0.296 ppb–1) × CS + 0.003 What is the Pb2+ level (in ppb) in a sample of blood if Ssamp is 0.397? SOLUTION To determine the concentration of Pb2+ in the sample of blood, we replace Sstand in the calibration equation with Ssamp and solve for CA It is worth noting that the calibration equation in this problem includes an extra term that is not in equation 5.3. Ideally, we expect the calibration curve to give a signal of zero when CS is zero. This is the purpose of using a reagent blank to correct the measured signal. The extra term of +0.003 in our calibration equation results from uncertainty in measuring the signal for the reagent blank and the standards. An external standardization allows a related series of samples to be analyzed using a single calibration curve. This is an important advantage in laboratories where many samples are to be analyzed or when the need for a rapid throughput of l i iti l t i i l f th t l t d C S A samp ppb === – . . . –. . . – 0 003 0 296 0 397 0 003 0 296 1 33 1 ppb ppb –1 Color plate 1 shows an example of a set of external standards and their corresponding normal calibration curve. x 1400-Fm 9/9/99 7:38 AM Page x
. End of chapter List of Key Terms The key terms introduced within the chapter are an (s. Jo winele-puint standardization (A M08) listed at the end of each chapter. Page references internal stard direct the student to the definitions in the text 120 residal crror (A. The summary provides the student with a brief 油 award additum in w review of the important concepts within the chapter. Sakra. sw 二如: the reproducible handling ef samples as Suggested Experiments annotated list of representative experiments is provided from the Journal of Chemical Education. 如每 the ume. MoM imkraents have calibration standards ungoed Suggested Readings flewin cnmmn and experiment hrip amnat she material in hu chapter h thr analytical laboratoy. Suggested readings give the student access to more comprehensive glassware(buret, Pipets, and SaandardiaaSon-Exlerad andar, atandard additices, discussion of the topics introduced vithin the chapter. lumctri glanwwae, weighing ampk, an prepari DPIC SUCCESTED READINGS References The references cited in the hapter are provided so the student can access them for further information 3I PROBLEMS Im以,山mam when working with a soid aapl, it allen is neccmrr to 4. Auple wa anal canont senta Problems -20 what is the tlue of the A variety of problems, many based on data from the analytical literature, examples of 吧蚀eγ⌒
List of Key Terms The key terms introduced within the chapter are listed at the end of each chapter. Page references direct the student to the definitions in the text. Summary The summary provides the student with a brief review of the important concepts within the chapter. Suggested Experiments An annotated list of representative experiments is provided from the Journal of Chemical Education. . . . End of Chapter y y 5E KEY TERMS aliquot (p. 111) external standard (p. 109) internal standard (p. 116) linear regression (p. 118) matrix matching (p. 110) method of standard additions (p. 110) multiple-point standardization (p. 109) normal calibration curve (p. 109) primary reagent (p. 106) reagent grade (p. 107) residual error (p. 118) secondary reagent (p. 107) single-point standardization (p. 108) standard deviation about the regression (p. 121) total Youden blank (p. 129) In a quantitative analysis, we measure a signal and calculate the amount of analyte using one of the following equations. Smeas = knA + Sreag Smeas = kCA + Sreag To obtain accurate results we must eliminate determinate errors affecting the measured signal, Smeas, the method’s sensitivity, k, and any signal due to the reagents, Sreag. To ensure that Smeas is determined accurately, we calibrate the equipment or instrument used to obtain the signal. Balances are calibrated using standard weights. When necessary, we can also correct for the buoyancy of air. Volumetric glassware can be calibrated by measuring the mass of water contained or delivered and using the density of water to calculate the true volume. Most instruments have calibration standards suggested by the manufacturer. An analytical method is standardized by determining its sensitivity. There are several approaches to standardization, including the use of external standards, the method of standard addition, and the use of an internal standard. The most desirable standardization strategy is an external standardization. The method of standard additions, in which known amounts of analyte are added to the sample, is used when the sample’s matrix complicates the analysis. An internal standard, which is a species (not analyte) added to all samples and standards, is used when the procedure does not allow for the reproducible handling of samples and standards. Standardizations using a single standard are common, but also are subject to greater uncertainty. Whenever possible, a multiplepoint standardization is preferred. The results of a multiple-point standardization are graphed as a calibration curve. A linear regression analysis can provide an equation for the standardization. A reagent blank corrects the measured signal for signals due to reagents other than the sample that are used in an analysis. The most common reagent blank is prepared by omitting the sample. When a simple reagent blank does not compensate for all constant sources of determinate error, other types of blanks, such as the total Youden blank, can be used. 5F SUMMARY Calibration—Volumetric glassware (burets, pipets, and volumetric flasks) can be calibrated in the manner described in Example 5.1. Most instruments have a calibration sample that can be prepared to verify the instrument’s accuracy and precision. For example, as described in this chapter, a solution of 60.06 ppm K2Cr2O7 in 0.0050 M H2SO4 should give an absorbance of 0.640 ± 0.010 at a wavelength of 350.0 nm when using 0.0050 M H2SO4 as a reagent blank. These exercises also provide practice with using volumetric glassware, weighing samples, and preparing solutions. Standardization—External standards, standard additions, and internal standards are a common feature of many quantitative analyses. Suggested experiments using these standardization methods are found in later chapters. A good project experiment for introducing external standardization, standard additions, and the importance of the sample’s matrix is to explore the effect of pH on the quantitative analysis of an acid–base indicator. Using bromothymol blue as an example, external standards can be prepared in a pH 9 buffer and used to analyze samples buffered to different pHs in the range of 6–10. Results can be compared with those obtained using a standard addition. 5G Suggested EXPERIMENTS The following exercises and experiments help connect the material in this chapter to the analytical laboratory. Experiments 1. When working with a solid sample, it often is necessary to bring the analyte into solution by dissolving the sample in a suitable solvent. Any solid impurities that remain are removed by filtration before continuing with the analysis. In a typical total analysis method, the procedure might read After dissolving the sample in a beaker, remove any solid impurities by passing the solution containing the analyte through filter paper, collecting the solution in a clean Erlenmeyer flask. Rinse the beaker with several small portions of solvent, passing these rinsings through the filter paper, and collecting them in the same Erlenmeyer flask. Finally, rinse the filter paper with several portions of solvent, collecting the rinsings in the same Erlenmeyer flask. For a typical concentration method, however, the procedure might state 4. A sample was analyzed to determine the concentration of an analyte. Under the conditions of the analysis, the sensitivity is 17.2 ppm–1. What is the analyte’s concentration if Smeas is 35.2 and Sreag is 0.6? 5. A method for the analysis of Ca2+ in water suffers from an interference in the presence of Zn2+. When the concentration of Ca2+ is 50 times greater than that of Zn2+, an analysis for Ca2+ gives a relative error of –2.0%. What is the value of the selectivity coefficient for this method? 6. The quantitative analysis for reduced glutathione in blood is complicated by the presence of many potential interferents. In one study, when analyzing a solution of 10-ppb glutathione and 1.5-ppb ascorbic acid, the signal was 5.43 times greater than that obtained for the analysis of 10-ppb glutathione.12 What is the selectivity coefficient for this analysis? The same study found that when analyzing a solution of 350-ppb methionine and 10-ppb glutathione the signal was 0 906 times less than that obtained for the analysis 3J PROBLEMS y y The role of analytical chemistry within the broader discipline of chemistry has been discussed by many prominent analytical chemists. Several notable examples follow. Baiulescu, G. E.; Patroescu, C.; Chalmers, R. A. Education and Teaching in Analytical Chemistry. Ellis Horwood: Chichester, 1982. Hieftje, G. M. “The Two Sides of Analytical Chemistry,” Anal. Chem. 1985, 57, 256A–267A. Kissinger, P. T. “Analytical Chemistry—What is It? Who Needs It? Why Teach It?” Trends Anal. Chem. 1992, 11, 54–57. Laitinen, H. A. “Analytical Chemistry in a Changing World,” Anal. Chem. 1980, 52, 605A–609A. Laitinen, H. A. “History of Analytical Chemistry in the U.S.A.,” Talanta 1989, 36, 1–9. Laitinen, H. A.; Ewing, G. (eds). A History of Analytical Chemistry. The Division of Analytical Chemistry of the American Chemical Society: Washington, D.C., 1972. McLafferty, F. W. “Analytical Chemistry: Historic and Modern,” Acc. Chem. Res. 1990, 23, 63–64. 1G SUGGESTED READINGS 1. Ravey, M. Spectroscopy 1990, 5(7), 11. 2. de Haseth, J. Spectroscopy 1990, 5(7), 11. 3. Fresenius, C. R. A System of Instruction in Quantitative Chemical Analysis. John Wiley and Sons: New York, 1881. 4. Hillebrand, W. F.; Lundell, G. E. F. Applied Inorganic Analysis, John Wiley and Sons: New York, 1953. 5. Van Loon, J. C. Analytical Atomic Absorption Spectroscopy. Academic Press: New York, 1980. 6. Murray, R. W. Anal. Chem. 1991, 63, 271A. 7. For several different viewpoints see (a) Beilby, A. L. J. Chem. Educ. 1970, 47, 237–238; (b) Lucchesi, C. A. Am. Lab. 1980, October, 113–119; (c) Atkinson, G. F. J. Chem. Educ. 1982, 59, 201–202; (d) Pardue, H. L.; Woo, J. J. Chem. Educ. 1984, 61, 409–412; (e) Guarnieri, M. J. Chem. Educ. 1988, 65, 201–203; (f) de Haseth, J. Spectroscopy 1990, 5, 20–21; (g) Strobel, H. A. Am. Lab. 1990, October, 17–24. 8. Hieftje, G. M. Am. Lab. 1993, October, 53–61. 9. See, for example, the following laboratory texts: (a) Sorum, C. H.; Lagowski, J. J. Introduction to Semimicro Qualitative Analysis, 5th ed. Prentice-Hall: Englewood Cliffs, NJ, 1977.; (b) Shriner, R. L.; Fuson, R. C.; Curtin, D. Y. The Systematic Identification of Organic Compounds, 5th ed. John Wiley and Sons: New York, 1964. 1H REFERENCES Problems A variety of problems, many based on data from the analytical literature, provide the student with practical examples of current research. Suggested Readings Suggested readings give the student access to more comprehensive discussion of the topics introduced within the chapter. References The references cited in the chapter are provided so the student can access them for further information. xi 1400-Fm 9/9/99 7:38 AM Page xi