title: Assessing the suitability of the OECD 29 guidance document to investigate the transformation and dissolution of silver nanoparticles in aqueous media.
abstract: The OECD guidance document No. 29 was designed to determine the rate and extend to which metals can produce soluble available ionic metal species. This transformation/dissolution protocol was applied to silver nanomaterials. The results prove that concentrations of released Ag(+) at pH 8 were nearly similar at all three different loadings. At pH 6, the concentration of Ag(+) was almost the same at loadings of 10 and 100 mg L(-1) AgNPs. However, the study showed changes in concentrations of nanoparticles and aggregates (operationally defined as the fraction passing a 0.2 µm filter). At the higher pH both the concentrations in the test medium of Ag(+) and of AgNPs (fraction < 0.2 µm) decreased. After 7 days of test duration, 71 µg L(-1) of Ag(+) was found in pH 6 medium (initial loading of 100 mg L(-1)). In pH 8 medium a maximum concentration of 29 µg L(-1) Ag(+) was measured (initial loading of 10 mg L(-1)). The maximum transformation from AgNPs to Ag(+) was 2.7% (27 µg L(-1)) in pH 8 medium (loading of 1 mg L(-1)) after 7 days. At an initial loading of 100 mg L(-1) AgNPs in medium at pH 8, only 0.03% (30 µg L(-1)) were transformed to Ag(+) after 7 days. At the loading of 1 mg L(-1) AgNPs all silver concentrations remain relatively constant for the duration of the test after 7 until 28 days. The results reveal that only low concentrations of Ag(+) are released from AgNPs under the applied conditions.
authors.affiliation: Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Auf dem Aberg 1, 57392 Schmallenberg, Germany. Electronic address: claus.wasmuth@ime.fraunhofer.de.
authors.forename: Claus
authors.initials: C
authors.lastname: Wasmuth
authors.affiliation: Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Auf dem Aberg 1, 57392 Schmallenberg, Germany.
authors.forename: Heinz
authors.initials: H
authors.lastname: Rüdel
authors.affiliation: Institute of Applied Microbiology, Research Centre for BioSystems, Land Use, and Nutrition (IFZ), Justus-Liebig-Universität Giessen, Germany.
authors.forename: Rolf-Alexander
authors.initials: RA
authors.lastname: Düring
authors.affiliation: Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Auf dem Aberg 1, 57392 Schmallenberg, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Klawonn
mesh_terms: D017408:Guidelines as Topic; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles / Q000737:chemistry*; D066150:Organisation for Economic Co-Operation and Development; D009994:Osmolar Concentration; D012834:Silver / Q000737:chemistry*; D012995:Solubility
chemical_list: D012834:Silver
keywords: AgNPs; Ion release kinetics; NM-300K; OECD 29; Silver nanoparticles; Transformation/dissolution testing