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Assessing the suitability of the OECD 29 guidance document to investigate the transformation and dissolution of silver nanoparticles in aqueous media

: Wasmuth, Claus; Rüdel, Heinz; Düring, Rolf-Alexander; Klawonn, Thorsten

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Chemosphere 144 (2016), S.2018-2023
ISSN: 0045-6535
ISSN: 0366-7111
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IME ()
AgNPs; silver nanoparticles; OECD 29; transformation/dissolution testing; ion release kinetics; NM-300K

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.