Characterization of Nanomaterials in Liquid Disperse Systems

Description

This book describes different aspects of characterization and detection of nanomaterials in liquid disperse systems, such as suspensions, emulsions and suspoemulsions. Natural and technical particulate nanomaterials (NMs) are often present in formulations and products consisting of several disperse phases and complex dispersion media. Specific interfacial properties of the particles, their interactions with each other and with the dispersion medium, have to be considered. For example, the interfacial properties determine whether the particles tend to be arranged in aqueous or lipid phases or at their phase boundaries. The interfacial properties are significantly influenced by the adsorption of dissolved species, i.e., they depend on the composition of the dispersion medium. This poses great challenges for the characterization of these nanoparticle systems and requires adequate preparation methods. The nanoparticle measurement techniques aim at a deep physico-chemical understanding of the dispersity state of nanoparticle systems. Since the dispersity state of nanoparticle systems in an application usually does not correspond to their original manufacturing process, the formulation of new or improved product properties is of decisive importance. The characterization of nanoparticles in complex formulations or matrices requires an adequate sample preparation based on an existing or yet to be developed Standard Operating Procedure (SOP). The structure of the SOPs includes the dispersion regulations, which are of essential importance for comparing reproducible results of nanoparticle measurement with respect to comparability and transferability worldwide. The aim is to separate and isolate relevant NMs with knowledge of the interrelationships. Preface Contents About the Author Nomenclature Latin Letters Greek Letters Indices Mathematical Symbols Constants Abbreviations 1 Introduction and Classification 1.1 Dispersity State of Nanomaterials 1.2 Scope of the Book 1.3 Analysis Tasks and Structure References 2 State of the Art and Knowledge About (Nanoparticulate) Disperse Systems 2.1 Characterization of Nanoparticles in Liquid Disperse Systems in Particle Metrology 2.1.1 Classification of Core Concepts of Nanoparticle Measurement Technology 2.1.2 Formulation Types of Nanoparticle Systems in Liquid Phases 2.1.3 Regulatory Assessment of Nanomaterials 2.1.4 Challenges and Content of the Characterization 2.2 Physico-Chemical Properties of “Nano”-Particle Systems 2.2.1 Electric Double Layer (EDL)—Models 2.2.2 Stability of Liquid Disperse Systems 2.2.3 Theory of Solubility Parameters 2.2.4 Wettability of Nanoparticles 2.3 Emulsification Processes with Contained Nanomaterials 2.3.1 Preparation of Emulsions Containing Nanomaterials 2.3.2 Stabilization and Destabilization Mechanisms of Emulsions 2.3.3 Dispersion (Emulsification) Processes of Suspoemulsions and Emulsions 2.4 Theory of the Characteristics of the Dispersion Processes 2.4.1 Mechanical Dispersion Methods 2.4.2 Application of the Volume-Based Energy Density Concept 2.4.3 Energy Density Concept in Nanoparticle Metrology and Research References 3 Main Principles of the Characterization of Nanoparticles in Liquid Disperse Systems 3.1 Analysis of Nanoparticles in Liquid Disperse Systems 3.1.1 Objectives, Fundamentals and Obstacles 3.1.2 Development and Application of Standard Operating Procedure (SOP) 3.1.3 Granulometric Methods of Nanoparticle Metrology 3.2 Possibilities for the Representation of Distribution Functions 3.2.1 Normalized Distribution Functions 3.2.2 Non-Normalized Distribution Functions 3.2.3 Transformed Density Function 3.2.4 Component Balance of the Distribution 3.3 Selected Nanoparticle Systems and Their General Properties 3.3.1 Synthetic Amorphous Silica (SAS)—SiO2 3.3.2 Pyrogenic Nanostructured Oxides—TiO2 and Al2O3 3.4 Selected Characterization Techniques 3.4.1 Laser Diffraction Spectroscopy—LD 3.4.2 Dynamic Light Scattering—DLS 3.4.3 Dynamic Ultramicroscopy—DUM 3.4.4 Optical Centrifugation Analysis—OPA 3.4.5 Acoustophoretic Mobility 3.4.6 Electrophoretic Mobility References 4 Knowledge Generating Experiments 4.1 Reproducible Dispersion with Defined Energy Input 4.1.1 Dispersion Techniques in Practice 4.1.2 Calibration Specification of Mechanical Dispersion Methods 4.1.3 Validation of Mechanical Dispersion—Practical Test 4.1.4 Sample Contamination During Dispersion 4.1.5 Discussion of the Results on Dispersion 4.2 Electrokinetic Properties and Stability Behavior of Nanoparticle Systems 4.2.1 Conservation of the Dispersity and Interfacial State of the Suspension 4.2.2 Comparability of Zeta-Potential Methods 4.2.3 From Fractal-Like Aggregates to Spherical SiO2 Particles 4.2.4 Measurement of the Zeta-Potential of Different Silica Types 4.2.5 Discussion of the Results and Consequences for SOPs 4.3 Extraction of Nanomaterials from Cosmetic Formulations 4.3.1 Procedure for the Development of Extraction Methods 4.3.2 Research of the Emulsification Process with Contained Nanomaterials 4.3.3 Discussion of Results and Consequences for SOPs References 5 Demonstration Experiments 5.1 Load-Dependent Dispersity State of Nanomaterials 5.1.1 Influence on the Measured Particle Size Distribution of SiO2 5.1.2 Dispersion Effectiveness of Direct Dispersion Methods 5.1.3 Discussion on Dispersion Effectiveness of Nanostructured Oxides 5.2 Dispersity State of Nanomaterials in Physiological Media 5.2.1 Nanomaterials in Simulated Lung Fluid 5.2.2 Nanomaterials in Simulated Gastrointestinal Passage 5.2.3 Discussion 5.3 Consideration of the Absolute Signal Strength of Optical Measurement Methods 5.3.1 Component Balance of the Distribution and Possibilities for Representation 5.3.2 Granulometric Data Analysis of Complex Nanoparticle Systems 5.3.3 Discussion on Characterization of Complex Nanoparticle Systems References 6 Conclusion and Discussion 6.1 Summary of the Results 6.2 Discussion 6.3 Outlook 6.4 Conclusion Appendix A Turbidity Measurements of Silicas in Different Media Comparison of the Sedimentation Velocity Transmission Profiles for Selected SAS Samples in Physiological Media Investigation of the Long-Term Stability of Formulated SAS Suspoemulsions Appendix B Composition of the Simulated Physiological Media Cell Culture Medium—F-12 K Appendix C Chemicals and Analytical Technology in the Laboratory Instrumentation to Control the Physico-Chemical Properties of Nanoparticle Systems Instruments for the Separation of Disperse and Continuous Phases Material Database—Chemicals Appendix D Technical Data of Mechanical Dispersion Techniques Paddle Stirrer Systems Ultrasonic Dispersion Systems Rotor–Stator Systems Uncited Reference