5 . 1 Analytical Methods 101

5 . 1 . 1 Nanoparticle Imaging: Size, Shape, and Chemical Composition . . . . 101

5 . 1 . 2 Compositional Analysis 108

5 . 1 . 2 . 1 Single Particle Mass Spectrometer 108

5 . 1 .2 .2 Particle-Induced X-Ray Emission (PIXE) 109

5 . 1 . 3 Surface Area: Product Characterization and Air Monitoring 109

5 . 1 . 3 . 1 The Brunauer Emmett Teller (BET) Method 109

5 . 1 .4 Size Distribution 110

5 . 1 .4 . 1 Electrostatic Classifiers 110

5 . 1 .4 . 2 Real-Time Inertial Impactor: Cascade Impactors 110

5 . 1 .4. 3 Electrical Low Pressure Impactor (ELPI) 111

5 . 2 Workplace Air Monitoring 112

5 . 2 . 1 Condensation Particle Counter (CPC) 113

5 . 2 .2 Surface Area: Total Exposure 113

5 . 3 Sampling and Analysis of Waters and Soils for Nanoparticles 114

5 .4 Nanotechnology Measurement Research and Future Directions 115

5 .4 . 1 . 2 U.S . Government-Sponsored Research 117

5 .4. 1 . 3 National Institute of Standards and Technology (NIST) . . . 117 5 4 2 European Union 118

5 5 Summary 119

References 119

The rapid explosion of production and use of engineered nanoparticles has outpaced the scientific community's ability to monitor their presence in the environment. Without measurement data, it is not possible to fully evaluate whether the promises of nanoparticles are accompanied by significant ecological or human health risks . Numerous national and international agencies and research groups have recognized this gap and put in place research programs to address it. However, the technical requirements for the detection and characterization of nanoparticles in complex environmental systems push the limits of current sampling techniques and instrumentation . In most cases, multiple complementary measurements are likely necessary to detect and understand the importance of nanoparticles in air, water, or soil because physical properties as well as chemical composition determine activity and environmental impact or risk . Environmental analyses of nanoparticles are not common offerings at commercial environmental laboratories at this time, and they are not likely to become so in the near future

In the manufacturing industry, the development and production of nanoparti-cle materials for commercial applications are supported by an array of analytical methods While numerous methods can successfully characterize the chemistry and physical properties of nanoparticles in relatively pure states and under defined conditions, the applicability of these methods to nanoparticles in environmental settings may be more limited . Once nanoparticles enter the environment, they may cluster to form larger particles, interact with particles from natural sources, or change chemically. Conventional environmental analysis methods as developed and standardized by the U.S . Environmental Protection Agency (EPA) are bulk analyses; they can detect the primary chemical constituents of nanoparticle materials but little else of use for characterizing risk from them In addition, the target nanoparticles may only be a minor component of an environmental sample and fall below the detection limits of standard EPA chemical analysis methods . Collection and separation of nanoparticles from larger environmental particles, when even possible, are difficult, and their analysis is in most cases time-consuming and costly. No standard methods with prescribed quality control requirements for environmental nanoparticle analyses exist, and only limited traceable standards have been developed

Aside from the technical challenges to nanoparticle measurement in environmental media, the lack of specific regulations limits the incentive for commercial environmental laboratories to put in place the costly instrumentation and the high degree of expertise that will be required to offer nanoparticle analyses to government, private industry, or public groups While there is some concern for possible environmental risks from nanoparticles, manufacturers, users, and site owners currently are not required to address these concerns with actual environmental measurement data As a result, most technical advances and data that do exist for environmental analyses have come from academic laboratories and governmental or privately funded research laboratories The applicability of regulatory statutes as discussed in Chapter 4 of this book continues to be debated . The Toxic Substances Control Act (TSCA), the Clean Water and Clean Air Acts (CWA, CAA), the Resource Conservation and Recovery Act (RCRA), and the Federal Insecticide, Fungicide, and Roden-ticide Act (FIFRA) drove method development for numerous industrial chemicals in the environment Regulatory requirements applicable to nanomaterials likewise would be expected to drive the development and standardization of environmental nanoparticle analytical methods for wider application, as well as to foster competition in an emerging market for laboratory services Instrumentation and staffing costs will, however, remain a barrier to entry into the field for most commercial laboratories currently offering environmental services

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