P R I N C I P L E S OF INSTRUMENTAL

ANALYSIS

FOURTH EDITION

Douglas A. Skoog Stanford University

James J. Leary James Madison University

Saunders College Publishing Harcourt Brace College Publishers Fort Worth Philadelphia San Diego

New York Orlando Austin San Antonio Toronto Montreal London Sydney Tokyo

Contents

1 Introduction 1 1A Classification of Analytical Methods 1 1B Types of Instrumental Methods 2 IC Instruments for Analysis 3 1D Selecting an Analytical Method 5 IE Questions and Problems 9

2 Operational Amplifiers in Chemical Instrumentation 10

2A Properties of Operational Amplifiers 10 2B Circuits Employing Operational

Amplifiers 12 2C Amplification and Measurement of

Transducer Signals 15 2D Application of Operational Amplifiers to

Voltage and Current Control 19 2E Application of Operational Amplifiers to

Mathematical Operations 20 2F Application of Operational Amplifiers to

Switching 24 2G Questions and Problems 24

3 Digital Electronics, Microprocessors, and Computers 29

3A Analog and Digital Signals 29 3B Counting and Arithmetic with Binary

Numbers 30 3C Basic Digital Circuit Components 32 3D Microprocessors and Microcomputers 36 3E Components of a Computer 39 3F Computer Programming 41 3G Applications of Computers 41 3H Computer Networks 43

4 Signals and Noise 46 4A Signal-to-Noise 46 4B Sources of Noise in Instrumental

Analyses 47 4C Signal-to-Noise Enhancement 49 4D Questions and Problems 56

5 Properties of Electromagnetic Radiation 58 5A An Overview 58 5B Electromagnetic Radiation 60 5C Quantum-Mechanical Properties of

Radiation 70 5D Questions and Problems 77

IX

Instruments for Optical Spectroscopy 6A Components of Optical Instruments 6B Radiation Sources 81 6C Wavelength Selectors 87 6D Sample Containers 97 6E Radiation Detectors 98 6F Signal Processors and Readouts 107 6G Fiber Optics 108 6H Instrument Designs 109 61 Questions and Problems 120

1 0 Atomic Spectroscopy Based Upon 79 Flame and Electrothermal

79 Atomizat ion 196 10A Sample Atomization 196 10B Types and Sources of Atomic

Spectra 198 IOC Flame Atomization 205 10D Atomic Absorption Spectroscopy 211 10E Flame Emission Spectroscopy 223 10F Atomic Fluorescence Spectroscopy 228 10G Questions and Problems 230

An Introduction to Molecular Ultraviolet/Visible and Near-Infrared Absorption Spectroscopy 123

7A Terms Employed in Absorption Spectroscopy 123

7B Quantitative Aspects of Absorption Measurements 126

7C Instruments for Absorption Measurements in the Ultraviolet, Visible, and Near-Infrared Regions 136

7D Question and Problems 147

Application of Molecular Ultraviolet/ Visible Absorption Spectroscopy 150

8A The Magnitude of Molar Absorptivities 150

8B Absorbing Species 150 8C Application of Absorption Measurement to

Qualitative Analysis 160 8D Quantitative Analysis by Absorption

Measurements 161 8E Photometrie Titrations 166 8F Photoacoustic Spectroscopy 168 8G Questions and Problems 170

Molecular Fluorescence, Phosphorescence, and Chemiluminescence 174 9A Theory of Fluorescence and

Phosphorescence 175 9B Instruments for Measuring Fluorescence and

Phosphorescence 18 3 9C Applications and Photoluminescence

Methods 188 9D Chemiluminescence 191 9E Questions and Problems 193

1 1 Emission Spectroscopy Based Upon Plasma, Are, and Spark Atomization 233 IIA Spectra from Higher-Energy Sources 234 IIB Emission Spectroscopy Based on Plasma

Sources 234 HC Emission Spectroscopy Based on Are and

Spark Sources 244 HD Questions and Problems 251

1 2 Infrared Absorption Spectroscopy 252 12A Theory of Infrared Absorption 253 12B Infrared Sources and Detectors 260 12C Infrared Instruments 263 12D Sample Handling Techniques 272 12E Qualitative Applications of Mid-Infrared

Absorption 275 12F Quantitative Applications 280 12G Internal-Reflection Infrared

Spectroscopy 283 12H Photoacoustic Infrared Spectroscopy 285 121 Near-Infrared Spectroscopy 285 12J Far-Infrared Spectroscopy 288 12K Infrared Emission Spectroscopy 288 12L Questions and Problems 288

1 3 Raman Spectroscopy 13A Theory of Raman Spectroscopy 297 13B Instrumentation 302 13C Applications of Raman Spectroscopy 13D Application of Other Types of Raman

Spectroscopy 306 13E Questions and Problems 308

296

304

CONTENTS Xi

1 4 Nuclear Magnetic Resonance Spectroscopy 310 14A Theory of Nuclear Magnetic

Resonance 311 14B Environmental Effects on NMR

Spectra 322 14C NMR Spectrometers 334 14D Applications of Proton NMR 340 14E Carbon-13 NMR 344 14F Application of NMR to Other Nuclei 348 14G Two-Dimensional Fourier Transform

NMR 350 14H Questions and Problems 351

1 5 X-Ray Spectroscopy 357 15A Fundamental Principles 357 15B Instrument Components 364 15C X-Ray Fluorescence Methods 373 15D X-Ray Absorption Methods 378 15E X-Ray Diffraction Methods 378 15F The Electron Microprobe 380 15G Questions and Problems 381

1 6 Analysis of Surfaces with Electron Beams 383 16A Electron Spectroscopy 383 16B The Scanning Electron Microscope and

Microprobe 394 16C Questions and Problems 399

1 7 Radiochemical Methods 401 17A Radioactive Isotopes 401 17B Instrumentation 408 17C Neutron Activation Methods 410 17D Isotope Dilution Methods 414 17E Questions and Problems 416

1 8 Mass Spectrometry 420 18A The Mass Spectrometer 422 18B Molecular Spectra from Various Ion

Sources 439 18C Identification of Pure Compounds by Mass

Spectrometry 448 18D Analysis of Mixtures by Hyphenated Mass

Spectral Methods 451 18E Quantitative Applications of Mass

Spectrometry 454 18F Surface Analysis by Mass

Spectrometry 458 18G Questions and Problems 459

1 9 An Introduction to Electroanalytical Chemistry 462 19A Electrochemical Cells 462 19B Cell Potentials 466 19C Electrode Potentials 466 19D Calculation of Cell Potentials from Electrode

Potentials 475 19E Currents in Electrochemical Cells 478 19F Types of Electroanalytical Methods 485 19G Questions and Problems 486

2 0 Potentiometrie Methods 489 20A Reference Electrodes 489 20B Metallic Indicator Electrodes 492 20C Membrane Indicator Electrodes 494 20D Molecular-Selective Electrode

Systems 503 20E Instruments for Measuring Cell

Potentials 506 20F Direct Potentiometrie Measurements 508 20G Potentiometrie Titrations 514 20H Questions and Problems 514

2 1 Coulometric Methods 517 21A Current-Voltage Relationships During

Electrolysis 517 21B An Introduction to Coulometric Methods of

Analysis 522 21C Potentiostatic Coulometry 523 21D Coulometric Titrations (Amperostatic

Coulometry) 527 21E Questions and Problems 531

2 2 Voltammetry 535 22A Excitation Signals in Voltammetry 536 22B Linear-Scan Voltammetry 536 22C Pulse Polarographic and Voltammetric

Methods 554 22D Stripping Methods 559 22E Voltammetry with Microscopic

Electrodes 562 22F Cyclic Voltammetry 563 22G Questions and Problems 565

2 3 Thermal Methods 568 23A Thermogravimetric Methods (TG) 568 23B Differential Thermal Analysis (DTA) 571

23C Differential Scanning Calorimetry (DSC) 575

23D Questions and Problems 577

An Introduction to Chromato­graphie Separations 24A A General Description of

Chromatography 579 24B Migration Rates of Species 581 24C Band Broadening and Column

Efficiency 585 24D Optimization of Column

Performance 592 24E Summary of Important Relationships for

Chromatography 598 24F Applications of Chromatography 598 24G Questions and Problems 601

2 8 Automated Methods of Analysis 681

579

28A An Overview of Automatic Instruments and Automation 681

28B Flow-Injection Analysis 683 28C Discrete Automatic Systems 690 28D Automatic Analyses Based Upon Multilayer

Films 696 28E Questions and Problems 700

A p p e n d i x 1 Evaluation of Analytical Data A-l a1A Precision and Accuracy A-l a1B Statistical Treatment of Random

Errors A-6 a1C Method of Least Squares

A-17 a1D Questions and Problems

A-19

Gas Chromatography 25A Principles of Gas-Liquid

Chromatography 606 25B Instruments for Gas-Liquid

Chromatography 607 25C Gas-Chromatographie Columns and Station

ary Phase 613 25D Applications of Gas-Liquid

Chromatography 619 25E Gas-Solid Chromatography 623 25F Questions and Problems 625

High-Performance Liquid Chromatography 628 26A ScopeofHPLC 629 26B Column Efficiency in Liquid

Chromatography 629 26C Instruments for Liquid

Chromatography 631 26D Partition Chromatography 642 26E Adsorption Chromatography 651 26F Ion Chromatography 654 26G Size-Exclusion Chromatography 659 26H Thin-Layer Chromatography 663 261 Questions and Problems 667

605 Appendix 2

Appendix 3

Some Electrical Circuit Components A-24 a2A Direct Current Circuits and

Measurements A-24 a2B Alternating Current Circuits

A-29 a2C Questions and Problems

A-39

Some Electronic Circuit Components and Devices A-43 a3A Semiconductors and Semiconduc-

tor Devices A-43 a3B Power Supplies and Regulators

A-49 a3C Readout Devices A-50

A p p e n d i x 4 Activity Coefficients A-54 a4A Properties of Activity

Coefficients A-54 a4B Experimental Evaluation of Ac­

tivity Coefficients A-55 a4C The Debye-Huckel Equation

A-56

A p p e n d i x 5 Some Standard and Formal Electrode Potentials A-58

Other Separation Methods 27A Supercritical Fluid Chromatography 27B Capillary Electrophoresis 675 27C Questions and Problems 680

A p p e n d i x 6 Compounds Recommended for the Prep-670 aration of Standard Solutions of Some 670 Common Elements A-62

Answers to Selected Problems A-64