DEVELOPMENT OF ICP-MS BASED NANOMETROLOGY TECHNIQUES FOR CHARACTERIZATION OF SILVER NANOPARTICLES IN ENVIRONMENTAL SYSTEMS by Denise Marie Mitrano A thesis submitted to the Faculty and the Board of Trustees of the Colorado School of Mines in partial fulfillment of the requirements for the degree of Philosophy of Science (Geochemistry). Golden, Colorado Date Signed: Denise Marie Mitrano Signed: Dr. James F. Ranville Thesis Advisor Golden, Colorado Date Signed: Dr. David T. W. Wu Professor and Head Department of Chemistry and Geochemistry ii ABSTRACT The ubiquitous use of goods containing nanoparticles (NPs) will lead inevitably to envi- ronmental release and interaction with biota. Methods to detect, quantify, and characterize NPs in environmental matrices are highlighted as one of the areas of highest priority re- search in understanding potential environmental and health risks. Specifically, techniques are needed to determine the size and concentration of NPs in complex matrices. Particu- lar analytical challenges include distinguishing NPs from other constituents of the matrix (i.e. natural particles, humic substances, and debris), method detection limits are often higher than exposure concentrations, and differentiating dissolved metal and NPs. This work focuses on the development and optimization of two methods that address a number of challenges for nanometrology: single particle (sp)ICP-MS and asymmetrical flow field flow fractionation (AF4)-ICP-MS. Advancements in the spICP-MS method included systematic studies on distinction between ionic and NP fractions, resolution of polydisperse NP samples, and defining the techniques’ dynamic range (in terms of both particle size and concentra- tion). Upon application of the technique, silver (Ag) NPs were discovered in raw wastewater treatment plant influent and effluent. Furthermore, methodical Ag NP stability studies de- termined the influence of particle capping agents and water chemistry parameters in a variety of synthetic, natural and processed waters. Method development for AF4-ICP-MS revolved around optimizing run conditions (i.e. operational flows, carrier fluid, membrane choice) to study detection limits, sample recovery, and resolution of polydisperse samples. Practical studies included sizing Ag NP in a sediment-dwelling, freshwater oligochaete (Lumbriculus variegatus) and the kinetics of accumulation of protein bound Ag+.Indirectcomparison, spICP-MS was found to be more versatile with less sample preparation and lower total ana- lyte detection limit (ng/L vs. g/L), though AF4-ICP-MS could detect smaller particle sizes (2 nm vs. 25 nm) and elucidate NP/matrix interactions for changes in particle hydrodynamic iii diameter. Additionally, spICP-MS afforded us the opportunity to determine the kinetic rate of Ag NP dissolution rate kinetics at environmentally relevent concentrations, the first study of its kind. We found significantly variable dissolution rates for differently capped NPs in addition to water chemistries. Tannic acid capping agent was least resistant to dissolution compared to citrate and PVP, while high concentrations of natural organic matter seemed to stabilize the particles over time in comparison to DI water. The residual chlorine in tap water increased the dissolution rates of all particles dramatically, which we hypothesize to be due to residual chlorine. Herein is described method development protocol and results of aforementioned studies comparing sp and AF4 ICP-MS and supporting their use as choice nanometrology techniques for quantitative environmental and toxicological studies. iv TABLE OF CONTENTS ABSTRACT ......................................... iii LISTOFFIGURES .....................................xii LISTOFTABLES ......................................xiv LISTOFABBREVIATIONS ................................xv ACKNOWLEDGMENTS ................................. xvii CHAPTER1 INTRODUCTION ...............................1 1.1 There’s plenty of room at the bottom: the rise of the nanotechnology industry . 2 1.2 Silver nanotechnology and the environment: bactericidal effects and consequences of nanosilver . 5 1.2.1 Ionic versus particle silver behavior . 5 1.2.2 Toxicityof(nano)silver: acellularapproach . .7 1.2.3 Nanosilver, bacteria, and wastewater treatment plants . 9 1.3 Potential transformations of silver nanoparticles in natural and treated watersystems ...................................13 1.3.1 Potential scenarios for nanoparticle release and subsequent transformation in the environment . 14 1.3.2 Alterations of silver nanoparticles in complex media . 16 1.3.3 Occurance of silver nanoparticles in wastewater treatment plants and subsequent transformation . 20 1.4 Nanometrology: analytical techniques for nanoparticle detection . 22 1.5 Purpose and Significance . 25 1.6 Organization of This Work . 27 v CHAPTER 2 INVESTIGATIONS FOR THE FEASIBILLITY OF DETECTING NANOPARTICULATE SILVER USING SINGLE PARTICLE INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY . 28 2.1 Abstract.......................................28 2.2 Introduction . 29 2.3 Materials and Methods . 32 2.3.1 AccompanyingStudies . 39 2.4 ResultsandDiscussion ............................... 39 2.4.1 ICP-MS Recovery . 39 2.4.2 Filtration .................................. 40 2.4.3 Analysis of Commercial Colloidal Silver Suppliment (ASAP) via Sp-ICP-MS .................................42 2.4.4 Wastewater Influent and Outfluent Samples . 44 CHAPTER 3 SILVER NANOPARTICLE CHARACTERIZATION USING SINGLE PARTICLE (SP)-ICP-MS AND ASYMMETRICAL FLOW FIELD FLOW FRACTIONATION (AF4)-ICP-MS . 48 3.1 Abstract.......................................48 3.2 Introduction . 49 3.3 Materials and Methods . 52 3.3.1 Materials . 52 3.3.2 Instrumentation-sp-ICP-MS . 53 3.3.3 Instrumentation-AF4-ICP-MS . 53 3.3.4 Data collection, conversion to particle size, and quality of analysis - spICP-MS . 54 3.3.5 Data collection, converstion to particle size, and quality of analysis - AF4-ICP-MS ................................57 vi 3.3.6 Size, detection limit, and resolution experimental parameters . 58 3.3.7 Multi-form analysis . 59 3.4 ResultsandDiscussion ............................... 60 3.4.1 Optimization for sp-ICP-MS . 60 3.4.2 MethodOptimizationforAF4-ICP-MS . 63 3.4.3 spICP-MS and AF4-ICP-MS comparison: Detection limit, NP size . 64 3.4.4 spICP-MS and AF4-ICP-MS comparison: Dynamic range, NP concentration . 66 3.4.5 spICP-MS and AF4-ICP-MS comparison: Resolution . 70 3.4.6 Multi-form analysis: Dissolved versus NP constituents. 74 3.4.7 Multi-formanalysis: NPcomplexes . 76 3.4.8 Multi-form analysis: Multiple metals analysis . 76 3.5 Conclusions . 77 3.5.1 Advantages and limitations of using spICP-MS in NP characterization . 78 3.5.2 Advantages and limitations of using AF4-ICP-MS in NP characterization............................... 79 3.5.3 Future development in the areas of spICP-MS and AF4-ICP-MS . 79 CHAPTER 4 TRACKING TRANSFORMATIONS OF SILVER NANOPARTICLES IN SYNTHETIC, NATURAL, AND PROCESSED WATERS USING SINGLE PARTICLE (SP)ICP-MS . 81 4.1 Introduction . 82 4.2 Materials . 85 4.3 Methods . 86 4.3.1 Instrumentation............................... 88 4.3.2 Data Collection, Conversion to Particle Size, and Quality Assurance . 88 vii 4.3.3 Characterization of Particle Stability and Silver Release . 89 4.3.4 Dissolution Rate Kinetics . 90 4.3.5 Preliminary Control Studies . 90 4.4 ResultsandDiscussion ............................... 91 4.4.1 Preliminary Control Studies . 91 4.4.2 Effects of Water Chemistry on Ag NP Stability - Mechanistic Studies . 94 4.4.3 Environmental Systems . 99 4.4.4 Processed Water Samples . 99 4.4.5 Comparison of Water Chemistry Effects . 101 4.4.6 Kinetic Rates of Dissolution . 101 4.5 Implications . 104 4.5.1 Effects of Water Chemistry on ENP Transformation in Aerobic Systems . 105 4.5.2 Effects of Water Chemistry on ENP Transformation in Anaerobic Systems . 107 4.5.3 Advancement of ENP Studies with the Use of spICP-MS . 108 CHAPTER 5 CONCLUSIONS . 109 5.1 Feasibility of detection nanoparticulate silver using spICP-MS . 109 5.2 Optimization and Comparison of nanometrology techniques . 110 5.3 Case Study: Application of spICP-MS to study dissolution kinetics of Ag NPs ........................................ 111 5.4 Collaborative efforts and future work . 113 REFERENCESCITED .................................. 117 APPENDIX A - AN INTRODUCTION TO FLOW FIELD FLOW FRACTIONATION AND COUPLING TO ICP-MS . 133 viii A.1 Introduction.................................... 133 A.2 FieldFlowFractionation . 133 A.3 FFFOperationandSeparationTheory . 134 A.4 CouplingFFFtoICP-MS ............................ 138 APPENDIX B - COUPLING FLOW FIELD FLOW FRACTIONATION TO ICP-MS FOR THE DETECTION AND CHARACTERIZATION OF SILVER NANOPARTICLES . 140 B.1 Introduction . 140 B.2 Nanometrology .................................. 141 B.3 Experimental . 142 B.3.1 Materials . 142 B.3.2 Instrumentation . 142 B.3.3 Daily Standards . 143 B.4 AnalyticalResults................................. 145 B.4.1 Resoution and detection limit . 145 B.4.2 MixedmetalanalysiswithflowFFF-ICP-MS . 146 B.5 Conclusions . 148 APPENDIX C - FIELD-FLOW FRACTIONATION COUPLED WITH ICP-MS FOR THE ANALYSIS OF ENGINEERED NANOPARTICLES IN ENVIRONMENTAL SYSTEMS . 149 C.1 EngineeredNanomaterials . 149 C.2 Potential for Environmental Impact . 150 C.3 AnalyticalMethodologies. 151 C.4 Field-Flow-Fractionation . 154 C.5 FFFCoupledwithICP-MS ........................... 155 ix C.6 ParticleSizeReferenceStandards . 157 C.7 Calibration Strategies . 159 C.8 Recovery . 159 C.9 Detection Limits