UK Centre for Ecology and Hydrology 2 articles published in JoVE Engineering UV-Vis Spectroscopic Characterization of Nanomaterials in Aqueous Media Ana C. Quevedo1, Emily Guggenheim1, Sophie M. Briffa1, Jessica Adams2,3, Stephen Lofts2, Minjeong Kwak4, Tae Geol Lee4, Colin Johnston5, Stephan Wagner6, Timothy R. Holbrook6, Yves U. Hachenberger7, Jutta Tentschert7, Nicholas Davidson1, Eugenia Valsami-Jones1 1School of Geography, Earth and Environmental Sciences, University of Birmingham, 2UK Centre for Ecology and Hydrology, 3Natural England, 4Center for Nanosafety Metrology, Korea Research Institute of Standards and Science (KRISS), 5Department of Materials, University of Oxford, 6Department of Analytical Chemistry, Helmholtz-Centre for Environmental Research, 7Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR) This study presents the benchmarking results for an interlaboratory comparison (ILC) designed to test the standard operating procedure (SOP) developed for gold (Au) colloid dispersions characterized by ultraviolet-visible Spectroscopy (UV-Vis), amongst six partners from the H2020 ACEnano project for sample preparation, measurement, and analysis of the results. Chemistry Nanoparticle Tracking Analysis of Gold Nanoparticles in Aqueous Media through an Inter-Laboratory Comparison Sophie M. Briffa1, Jo Sullivan2, Agnieszka Siupa2, Pauline Carnell-Morris2, Michele Carboni2, Kerstin Jurkschat3, Ruud J. B. Peters4, Carolin Schultz5, Kang Hee Seol6, Sook-Jin Kwon6, Sehee Park7, Tae Hyun Yoon6,7, Colin Johnston3, Stephen Lofts8, Eugenia Valsami-Jones1 1School of Geography, Earth and Environmental Sciences, University of Birmingham, 2Malvern Panalytical, 3Department of Materials, University of Oxford, 4Wageningen Food Safety Research, 5UK Centre for Ecology & Hydrology, 6Institute for Next Generation Material Design, Hanyang University, 7Department of Chemistry, College of Natural Sciences, Hanyang University, 8UK Centre for Ecology & Hydrology The protocol described here aims to measure the hydrodynamic diameter of spherical nanoparticles, more specifically gold nanoparticles, in aqueous media by means of Nanoparticle Tracking Analysis (NTA). The latter involves tracking the movement of particles due to Brownian motion and implementing the Stokes-Einstein equation to obtain the hydrodynamic diameter.