title: Quantification of Carbon Nanotubes in Environmental Matrices: Current Capabilities, Case Studies, and Future Prospects.
abstract: Carbon nanotubes (CNTs) have numerous exciting potential applications and some that have reached commercialization. As such, quantitative measurements of CNTs in key environmental matrices (water, soil, sediment, and biological tissues) are needed to address concerns about their potential environmental and human health risks and to inform application development. However, standard methods for CNT quantification are not yet available. We systematically and critically review each component of the current methods for CNT quantification including CNT extraction approaches, potential biases, limits of detection, and potential for standardization. This review reveals that many of the techniques with the lowest detection limits require uncommon equipment or expertise, and thus, they are not frequently accessible. Additionally, changes to the CNTs (e.g., agglomeration) after environmental release and matrix effects can cause biases for many of the techniques, and biasing factors vary among the techniques. Five case studies are provided to illustrate how to use this information to inform responses to real-world scenarios such as monitoring potential CNT discharge into a river or ecotoxicity testing by a testing laboratory. Overall, substantial progress has been made in improving CNT quantification during the past ten years, but additional work is needed for standardization, development of extraction techniques from complex matrices, and multimethod comparisons of standard samples to reveal the comparability of techniques.
authors.affiliation: Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Elijah J
authors.initials: EJ
authors.lastname: Petersen
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology , Überlandstrasse 133, CH-8600 Dübendorf, Switzerland.
authors.forename: D Xanat
authors.initials: DX
authors.lastname: Flores-Cervantes
authors.affiliation: Agroscope, Institute of Sustainability Sciences ISS , 8046 Zurich, Switzerland.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Bucheli
authors.affiliation: Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Lindsay C C
authors.initials: LC
authors.lastname: Elliott
authors.affiliation: Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Fagan
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology , Überlandstrasse 133, CH-8600 Dübendorf, Switzerland.|Agroscope, Institute of Sustainability Sciences ISS , 8046 Zurich, Switzerland.
authors.forename: Alexander
authors.initials: A
authors.lastname: Gogos
authors.affiliation: Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Shannon
authors.initials: S
authors.lastname: Hanna
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology , Überlandstrasse 133, CH-8600 Dübendorf, Switzerland.
authors.forename: Ralf
authors.initials: R
authors.lastname: Kägi
authors.affiliation: Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Mansfield
authors.affiliation: Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Antonio R Montoro
authors.initials: AR
authors.lastname: Bustos
authors.affiliation: Department of Chemical and Environmental Engineering, Yale University , New Haven, Connecticut 06520, United States.
authors.forename: Desiree L
authors.initials: DL
authors.lastname: Plata
authors.affiliation: Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Vytas
authors.initials: V
authors.lastname: Reipa
authors.affiliation: School of Sustainable Engineering and The Built Environment, Arizona State University , Box 3005, Tempe, Arizona 85278-3005, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: Westerhoff
authors.affiliation: Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Winchester
mesh_terms: D004777:Environment; D006801:Humans; D057230:Limit of Detection; D037742:Nanotubes, Carbon / Q000633:toxicity*
chemical_list: D037742:Nanotubes, Carbon