Analytical Techniques in the Sciences: Analytical Instrumentation Performance Characteristics and Quality

318 Pages·2000·21.49 MB·English

ANALYTICAL INSTRUMENTATION
PERFORMANCE CHARACTERISTICS
AND QUALITY
Analytical Techniques in the Sciences (AnTS)
Series Editor: David J. Ando, Consultant, Dartford, Kent, UK
A series of open learning/distant learning books which covers all of the major
analytical techniques and their application in the most important areas of physical,
life and materials sciences.
Forthcoming Titles
Polymer Analysis
Barbara H. Stuart, University of Technology, Sydney, Australia
Electroanalytical Chemistry: Principals and Fundamental Concepts
Paul M. S. Monk, Manchester Metropolitan University, Manchester, UK
Environmental Analysis
Roger N. Reeve, University of Sunderland, UK
ANALYTICAL
INSTRUMENTATION
PERFORMANCE
CHARACTERISTICS
AND QUALITY
Graham Currell
University of the West of England at Bristol, Bristol, UK
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Contents
Series Preface xv
Preface xvii
Acronyms, Abbreviations and Symbols xxi
About the Author xxvii
1 Analytical Measurements 1
1.1 Analytical Procedures 1
1.1.1 Calibration 2
1.2 Analytical Instrument 3
1.3 Data Output 4
1.4 Error, Uncertainty and Reliability 5
1.4.1 'Types of Error 7
1.4.2 Precision, Repeatability and Reproducibility 8
1.5 Analytical Method Characteristics 9
1.5.1 Method Precision 11
1S .2 Ruggedness 11
1.5.3 Selectivity (and Specificity) 13
References 14
2 Uncertainty and Random Error 15
2.1 Introduction 15
2.2 Probability Distribution of Errors 15
2.2.1 Normal Distribution 16
2.2.2 Rectangular Distribution 17
V.l.l.l Analytical Instrumentation
2.3 Expression of Uncertainty 18
2.4 Propagation of Errors - Combined Uncertainty 19
2.4.1 Addition and Subtraction 20
2.4.2 Multiplication and Division 20
2.4.3 Powers 21
2.4.4 Functions 21
References 23
3 Instrument Performance Characteristics 25
3.1 of Characteristics 25
Types
3.1.1 Experimental Conditions - I and I(u) 27
Types
3.1.2 Instrument Response - I1 and II(u) 27
Types
3.2 Generic Response Characteristics 27
3.2.1 Responsivity 29
3.2.2 Noise 31
3.2.3 Offset and Drift 31
3.2.4 Linearity and Linear Dynamic Range 32
3.2.5 Instrument Selectivity (Specificity) 35
3.3 Detectability Characteristics 36
3.4 Interaction between Characteristics 39
3.5 Memory Effects 40
3.6 Specifications 41
References 43
4 Quality Systems in Analytical Measurements 45
4.1 Introduction 45
4.2 Why is a Quality System Needed? 46
4.2.1 Collaborative Trials 47
4.3 What is a Quality System? 47
4.4 Benefits of a Quality System 50
4.5 Top-Down and Bottom-Up 51
4.6 Approaches to Quality 53
4.7 Quality Standards and Accreditation 54
4.8 Valid Analytical Measurement (VAM) Programme 56
4.9 Proficiency Testing and Certified Reference Materials 57
4.10 Validated Methods 57
4.1 1 System Suitability Testing 58
4.12 Equipment Qualification 59
4.13 Quality Control of Instrument Performance 63
References 65
Contents ix
uv-
5 Visible Spectrophotometer Systems 67
5.1 Basic (Single-Beam) System 67
5.2 Operation of a Single-Beam Instrument 70
5.2. I Without Microprocessor Memory 70
5.2.2 With Microprocessor Memory 72
5.3 Double-Beam Systems 72
5.4 Wavelength Scanning 74
5.5 System Performance 75
5.6 Spectral Characteristics 76
5.6.1 Wavelength Accuracy and Precision 76
5.6.2 Spectral Bandwidth 76
5.6.3 Stray Light 77
5.7 Photometric Uncertainties in Absorbance and Transmittance 79
5.7.1 Tracing Uncertainties in Absorbance and Transmittance 81
5.7.2 Drift in Source Output 81
5.7.3 Thermal (Johnson) Noise in the Detection System 82
5.7.4 Shot Noise in the Detection System 83
5.7.5 Combined Photometric Uncertainties 84
5.8 Photometric Characteristics 86
5.8.1 Accuracy, Precision and Noise 86
5.8.2 Baseline Flatness and Baseline Stability (Drift) 87
5.8.3 Photometric Linearity 87
5.8.4 Operational Wavelength Range 88
6 Atomic Spectroscopy 91
6.1 Radiation Processes 91
6.2 Absorption Spectroscopy 93
6.2.1 Flame Atomization 95
6.2.2 Graphite Furnace Atomization 96
6.3 Background Correction for Absorption Systems 96
6.3.1 Continuous-Source Method 97
6.3.2 Zeeman Method 97
6.3.3 Smith-Hieftje Method 98
6.4 Plasma Emission Spectroscopy 99
6.5 Performance Characteristics 100
References 103
7 Fourier-Transform Infrared Spectrophotometers 105
7.1 Basic System 105
7.1.1 Background Spectrum 107
Analytical Instrumentation
X
7.2 Michelson Interferometer 108
7.2.1 Transmittance of the Michelson Interferometer 109
7.2.2 Use of Laser Light 112
7.3 Interferogram - Approach I 112
7.3.1 Without Sample 112
7.3.2 With Sample 114
7.3.3 Information in the Interferogram 114
7.4 Interferogram - Approach 115
I1
7.4.1 Interferogram and its Fourier Transform 115
7.4.2 Resolution 117
7.4.3 Instrument Lineshape 118
7.4.4 Apodization 120
7.5 Advantages of FTIR Spectrophotometry 12 1
7.6 Performance Characteristics 123
8 System Characteristics of Chromatography and High
Gas
Performance Liquid Chromatography 125
8.1 Introduction 125
8.2 Retention Time and Capacity Factor 128
8.3 Peak Shape and Asymmetry 129
8.4 Column Efficiency 130
8.5 Separation Factor and Resolution 133
8.6 Detector Response 135
8.7 System Performance 136
References 139
9 High Performance Liquid Chromatography 141
9.1 Basic System 141
9.2 Pumping System 145
9.2.1 Performance Tests 146
9.2.2 Syringe Pump 14 7
9.2.3 Reciprocating Pumps 148
9.2.4 Gradient Systems 150
9.3 Detectors 150
9.3.1 Variable-Wavelength UV Detector 15 1
9.3.2 Diode-A rray Detector 152
9.3.3 Fluorescence Detector 154
9.3.4 Refractive-Index Detector 155
9.4 Performance Characteristics for HPLC Systems 155
References 158
Contents xi
10 Chromatography 159
Gas
10.1 Basic System 159
10.1.1 Gas-Flow Control 160
10.1.2 Oven 161
10.2 Injection Systems 162
10.3 Detectors 164
10.3.1 Thermal-Conductivity Detector 166
10.3.2 Flame-Ionization Detector 167
10.3.3 Flame-Photometric Detector 168
10.3.4 Electron-Capture Detector 168
11 Capillary Electrophoresis 171
11.1 Basic System 171
1 1.2 Performance Characteristics 173
1 1.2.1 Migration Time 173
11.2.2 Effect of Temperature 175
1 1.2.3 Efficiency 176
1 1.2.4 Resolution 178
11.3 Detection 179
1 1.4 Alternative Modes of Operation 180
References 182
12 Mass Spectrometry Systems 183
12.1 Basic Systems 183
12.1.1 Performance Characteristics 185
12.2 Hybrid Coupling Systems 187
12.2.1 Gas Chromatography-Mass Spectrometry 187
12.2.2 Liquid Chromatography- Mass Spectrometry 188
12.2.3 Capillary Electrophoresis-Mass Spectrometry 189
12.2.4 Inductively Coupled Plasma Mass Spectrometry 190
References 191
13 Signals 193
13.1 Introduction 193
13.2 Types of Signals 194
13.2.1 Digital Signals 195
13.2.2 Sampling of Analogue Signals 197
13.3 Harmonic (Sine or Cosine) Waves 198
13.3.1 Addition of Sine Waves 20 1