Agricultural and Food Electroanalysis

ALBERTO ESCARPA Analytical Chemistry, Physical Chemistry and Chemical Engineering Department, University of Alcala, Spain MARÍA CRISTINA GONZÁLEZ Analytical Chemistry, Physical Chemistry and Chemical Engineering Department, University of Alcala, Spain MIGUEL ÁNGEL LÓPEZ Analytical Chemistry, Physical Chemistry and Chemical Engineering Department, University of Alcala, Spain

List of Contributors xv

Preface xix

1. Electroanalysis and Food Analysis 1
Paloma Yá˜nez-Sede˜no and José M. Pingarrón

1.1 Introduction and Adequacy of Electroanalysis for Food Analysis 1

1.2 Methodologies Related to Measurement Techniques 2

1.2.1 Continuous Detection Methods 2

1.2.2 Stripping Analysis 5

1.2.3 Potentiometry and Chronopotentiometry 7

1.2.4 Electronic Tongues 7

1.2.5 Impedance Spectroscopy 9

1.3 Electrochemical Sensors and Biosensors for Food Components 9

1.3.1 Molecularly Imprinted Electrodes 9

1.3.2 Enzyme Biosensors 10

1.3.3 Affinity Biosensors 12

1.4 Nanomaterials for Electrochemical Analysis of Food 14

1.5 Future Trends 16

Acknowledgments 16

References 16

Part I Electroanalytical Techniques in Batch and Continuous Systems in Food Analysis 21

2. Voltammetric Techniques 23
Sandra Mendoza, Erika Bustos, Juan Manr´ýquez and Luis A. God´ýnez

2.1 Introduction 23

2.2 An Overview of Sweep Potential Electrochemical Techniques 23

2.2.1 Linear Sweep Voltammetry/Cyclic Voltammetry 25

2.2.2 Pulse Voltammetry Techniques 27

2.2.3 Normal Pulse Voltammetry 27

2.2.4 Differential Pulse Voltammetry 28

2.2.5 Square Wave Voltammetry 28

2.2.6 Stripping Voltammetry 29

2.3 Applications of Voltammetric Techniques in Food Analysis 31

2.3.1 Food Contaminants: Heavy Metals, Pesticides, and Toxic Substances 31

2.3.2 Trace Essential Elements 35

2.3.3 Food Additives 35

2.3.4 Nutraceuticals: Phenolic Acids, Flavonoids, and Others 40

2.4 Concluding Remarks 44

Abbreviations 44

References 44

3. Flow-Injection Analysis with Electrochemical Detection 49
Fabiana Silva Felix and Lúcio Angnes

3.1 Introduction 49

3.2 Screening the Literature 51

3.3 Voltammetry under Flowing Stream 52

3.4 Flow Injection Analysis Principles 52

3.4.1 Liquid Propulsion in FIA 54

3.4.2 Methods of Sample Introduction in an FIA System 56

3.4.3 Flow Cell Designs 57

3.5 Batch Injection Analysis Principles 58

3.6 Sequential Injection Analysis Principles 60

3.7 Applications 61

3.7.1 FIA and Voltammetric Detection–A Happy Marriage 61

3.7.2 BIA with Voltammetric Detection 64

3.7.3 SIA with Voltammetric Detection 65

3.8 Advantages of Voltammetry under Flowing Stream 66

3.9 Concluding Remarks 67

Acknowledgments 67

References 67

4. HPLC Techniques with Electrochemical Detection 73
Manuel Chicharro Santamar´ýa, Mónica Moreno Barambio and Alberto Sánchez Arribas

4.1 Introduction 73

4.2 Fundamentals 75

4.2.1 Electrochemical Cell 75

4.2.1.1 Electrode Materials 76

4.2.1.2 Flow-Cell Designs 77

4.2.1.3 Operation Modes 80

4.2.2 Development of HPLC-ED Methods 85

4.2.2.1 Getting Started 86

4.2.2.2 Hydrodynamic Voltammograms 86

4.2.2.3 Mobile Phase Composition 87

4.2.2.4 Temperature 89

4.2.2.5 Flow Rate 90

4.2.2.6 Electrode Treatment 90

4.2.2.7 Gradient Elution 91

4.2.2.8 Maintenance of HPLC-ED Systems 91

4.3 Analytical Designs and Performance 92

4.3.1 Natural Constituents 92

4.3.1.1 Carbohydrates 92

4.3.1.2 Amino Acids 94

4.3.1.3 Vitamins 96

4.3.1.4 Natural Phenolic Compounds 97

4.3.2 Nonanthropogenic Contaminants 98

4.3.2.1 Biogenic Amines 98

4.3.2.2 Mycotoxins 100

4.3.3 Anthropogenic Contaminants 101

4.3.3.1 Antibiotics 101

4.3.3.2 Pesticides (Herbicides, Insecticides, and Fungicides) 102

4.4 Concluding Remarks 104

References 105

5. Capillary Electrophoresis with Electrochemical Detection 117
Gang Chen

5.1 Introduction 117

5.2 Separation Techniques in Agricultural and Food Analysis 118

5.3 ECD in the CE Analysis of Foods and Agricultural Products 119

5.3.1 Amperometric Detection 119

5.3.2 Conductivity Detection and Potentiometric Detection 120

5.4 Instrumentations of CE-ECD 121

5.5 Determination of Nutritions by CE-ECD 122

5.5.1 Amino Acids and Peptides 122

5.5.2 Carbohydrates 124

5.5.3 Vitamins 126

5.5.4 Ions 127

5.6 Determination of Phenolic Compounds by CE-ECD 127

5.6.1 Phenols in Tea 127

5.6.2 Phenols in Coffee 127

5.6.3 Phenols in Wines 127

5.6.4 Phenols in Herbal Drugs 128

5.6.5 Flavones in Herbal Drugs 128

5.7 Determination of Purines by CE-ECD 130

5.8 Determination of Food Additives by CE-ECD 130

5.8.1 Preservatives 130

5.8.2 Antioxidants 131

5.8.3 Colors 131

5.8.4 Artificial Sweeteners 131

5.9 Summary 131

Abbreviations 132

Acknowledgments 132

References 133

Part II Electrochemical Sensing in Food Analysis 137

6. Microelectrode Designs 139
Jonathan P. Metters and Craig E. Banks

6.1 Introduction 139

6.2 Microfabrication Techniques 142

6.2.1 Lithography and Related Processes (Deposition, Sputtering, Other Relevant Technologies) 142

6.3 Screen-Printing for Producing Electrochemical Sensors 149

6.3.1 Improving Mass Transport 151

6.3.2 Metal Oxide Electrodes, Metal and Nano and Micro Modified Screen-Printed Sensors 159

6.4 Conclusions and Perspectives 161

References 161

7. Potentiometric Sensors 169
Geza Nagy and L´ývia Nagy

7.1 Introduction 169

7.2 The Types of Potentiometry 169

7.2.1 Potentiometric Stripping Analysis 170

7.2.2 Zero Current Potentiometry 171

7.2.3 Direct Potentiometry 175

7.2.4 Titrimetric Methods 177

7.3 The Selectivity of Ion-selective Electrodes and Its Determination 178

7.3.1 The Selectivity Coefficient 178

7.3.2 Separate Solution and Mixed Solution Methods 178

7.3.2.1 Separation Solution Methods 179

7.3.2.2 Mixed Solution Methods 180

7.4 Measuring Electrodes Used in Potentiometric Analysis 181

7.4.1 Ion-selective Field Effect Transistors 183

7.4.2 Severinghaus-type Probes 183

7.4.3 Potentiometric Enzyme Electrodes 184

7.5 Special Tasks 185

7.5.1 pH Measurements 185

7.5.2 Miscellaneous Analytical Tasks by Potentiometric Methods 190

7.6 Application of Potentiometric Measurements for Anions 191

7.6.1 Determination of Chloride Ion Concentration 191

7.6.1.1 Measurement of Cl− Concentration in Milk 192

7.6.1.2 Measurement of Cl− Concentration in Meat and Meat Products 192

7.6.1.3 Measurement of Cl− Concentration in Butter 192

7.6.1.4 Measurement of Cl− Concentration in Mayonnaise 192

7.6.1.5 Measurement of Cl− Concentration in Soil Samples 192

7.6.1.6 Chloride Ion Determination in Fruit Juice 193

7.6.2 Determination of Fluoride Ion Concentration 193

7.6.2.1 Fluoride Content of Wines 194

7.6.3 Applications of EPA Methods for Anion and Cation Analysis 194

7.6.4 Determination of Potassium Ion Concentration 195

7.6.5 Determination of Nitrate Ion Concentration 195

7.6.5.1 Nitrate Contain of Vegetables 195

7.6.6 Determination of Calcium Ion Concentration 197

7.6.7 Determination of Sweetening Additive Concentration 197

7.6.8 Determination of Fumaric Acid Concentration 197

7.6.8.1 Measuring the Fumarate Content in Gelatin 197

7.6.9 Quantification of Food Preservatives 198

7.6.9.1 Quantification of Sorbate 198

7.6.9.2 Quantification of Benzoate 198

7.6.10 Determination of Aluminum Ion Concentration 199

7.6.11 Methods for Detecting Histamine 199

References 200

8. Electrochemical Enzyme Biosensors 207
Ilaria Palchetti and Marco Mascini

8.1 Introduction 207

8.2 General Features of Enzyme Biosensors 209

8.2.1 Enzyme Biosensor Assembly 212

8.2.2 Enzyme Biosensor Stability 213

8.2.3 Biosensors Based on the Principle of Enzyme Inhibition 213

8.3 Analytical Features of Enzyme Based Biosensors 214

8.3.1 Biosensor Calibration 214

8.3.2 Biosensor Calibration for Determination of Inhibitors 215

8.3.3 Practical Aspects 215

8.3.3.1 Response Time 215

8.3.3.2 Thickness of the Enzyme Layer 216

8.3.3.3 Effect of Additional Membranes 216

8.4 Examples of Electrochemical Enzymatic Biosensors for Food Analysis 216

8.4.1 Detection of Pesticides 217

8.5 Conclusion 219

References 220

9. Electrochemical Immunosensors 223
M. Teresa Fernández-Abedul, M. Bego˜na González-Garc´ýa and Agust´ýn Costa-Garc´ýa

9.1 Introduction 223

9.2 Defining the Problem: The Targets 225

9.3 Recognizing the Target 231

9.3.1 Antibodies 231

9.3.2 Antigens 236

9.4 Immunosensing Architectures 236

9.4.1 Components of the Sensing Layer 238

9.4.2 Surface Engineering Procedures 256

9.4.3 Renewable Solid Surfaces 259

9.5 Performing Affinity Interactions for Molecular Recognition 260

9.6 Transducing Immunological Events 263

9.6.1 Electrode Materials and Types 263

9.6.1.1 Film Electrodes 264

9.6.2 Electrochemical Detection Methodologies 266

9.6.2.1 Label-Free Approaches 267

9.6.2.2 Amperometric Response to Labels 270

9.7 Advancing in Real Immunosensing 274

9.7.1 Multiplexed Determinations 275

9.7.2 Automation of Immunosensors 277

9.8 Processing Data 278

9.9 Conclusions 278

Abbreviations 280

References 283

10. Electrochemical Genosensors 295
Briza Pérez-López and Arben Merkoçi

10.1 General Introduction on Electrochemical Genosensors 295

10.1.1 Operation Principles 296

10.1.1.1 Label-Free (Direct) Detection 296

10.1.1.2 Label-Based (Indirect) Detection 300

10.2 Detection Methodologies 302

10.2.1 Voltammetric/Stripping 303

10.2.2 Potentiometric 304

10.2.3 Impedimetric 306

10.2.4 Conductometric 306

10.3 Applications 307

10.3.1 Species Identification 307

10.3.2 Contaminant Monitoring 309

10.4 Conclusions and Future Trends 311

Acknowledgments 311

References 311

11. Electrochemical Biosensors Based on Nanomaterials 317
Joseph Wang

11.1 Why Nanoscale Materials? 317

11.2 Nanowires, Nanotubes, and Nanoparticles 317

11.3 Nanomaterial-based Electrochemical Biosensors 319

11.3.1 Nanomaterial-based Biocatalytic Sensors 319

11.3.2 Nanomaterial-based Bioaffinity Sensors 321

11.4 Future Prospects 325

References 326

12. Electrochemical Sensing on Microfluidic Chips 331
Alberto Escarpa, Mar´ýa Cristina González and Miguel A. López

12.1 Electrochemical Detection Implementation in Microfluidic Chips 331

12.2 Microchip Electrophoresis with Electrochemical Detection for Food Analysis 335

12.2.1 Microchip Electrophoresis with Amperometric Detection for Organic Food Analytes 335

12.2.2 Microchip Electrophoresis with Amperometric Detection for Inorganic Food Analytes 341

12.2.3 Microchip Electrophoresis with Conductometric Detection for Food Analysis 341

12.3 Microfluidic Chips with Nanomaterial-Based Electrochemical Detection for Food Analysis 342

12.4 Microfluidic Electrochemical Biosensing Chips for Food Analysis 346

12.5 Outlook 350

Acknowledgments 351

Acronyms 351

References 352

13. Nanoelectrochemistry Applications Based on Electrospinning 357
Matteo Scampicchio, Maria Stella Cosio, Solomon Lemma Mengistu and Saverio Mannino

13.1 A Note on Nanoelectrochemistry 357

13.2 Electrochemical Sensors Modified with Nanofibrous Membranes 358

13.3 Introduction to Electrospinning 359

13.4 Applications of Electrochemical Sensors Based on Electrospinning 361

13.4.1 Nanofibrous Membranes as Coating Material 361

13.4.2 High Permeability 362

13.4.3 Selective Barrier to Diffusion 362

13.4.4 Conducting Nanofibrous Membranes 364

13.4.5 Biosensor Based on Nanofibrous Membranes 369

References 374

14. Electrochemical Impedance Spectroscopy 381
Araceli González-Cortés

14.1 Introduction 381

14.2 Impedance Spectroscopy–Theoretical Background 382

14.3 Chemical Sensors 387

14.4 Electrochemical Biosensors Based on Impedance Spectroscopy 390

14.4.1 Enzymatic Biosensors 391

14.4.2 Immunosensors 392

14.4.2.1 Impedimetric Immunosensors Using Interdigitated Array Microelectrodes 403

14.4.3 Genosensors and Aptasensors 406

14.5 Nonelectrochemical Interfacial Impedance 410

14.6 Conclusions and Perspectives 414

References 415

Part III Industrial Implications 421

15. Electroanalysis in Food Process Control 423
Maria Stella Cosio, Simona Benedetti, Matteo Scampicchio and Saverio Mannino

15.1 Sensors in Food Process 426

15.2 Electronic Nose 429

15.3 Electronic Nose Technologies 430

15.3.0.1 Metal Oxide Semiconductors 431

15.3.0.2 Metal Oxide Semiconductor Field-Effect Transistors 431

15.3.0.3 Conducting Organic Polymers 431

15.3.0.4 Piezoelectric Crystal Sensors 432

15.4 Electronic Noses for the Food Industry 433

15.5 Electronic Tongue 434

15.6 Pattern Recognition Models 436

15.7 Sampling 437

15.8 Conclusions 439

References 439

16. Instrumental Aspects of Food Analysis by Electrochemical Methods 443
Wendell K. T. Coltro, Maria F. Mora and Carlos D. Garcia

16.1 Introduction 443

16.2 Principles 444

16.3 Instrumentation for Electrochemical Detection 445

16.3.1 Instruments for Voltammetric Techniques 445

16.3.1.1 Amperometry 445

16.3.1.2 Pulsed Amperometric Detection 446

16.3.1.3 Voltammetry 447

16.3.2 Instrumentation for Potentiometric Techniques 448

16.3.3 Instruments for Conductometric Techniques 449

16.3.4 Instruments Developed for Portability 451

16.3.5 Low-Cost Potentiostats 455

16.3.6 Remotely Controlled Instruments 459

16.3.7 Electrochemical Detectors Coupled to Microchip Capillary Electrophoresis 460

16.4 Conclusions 464

Acknowledgments 464

References 464

Index 479