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EC number: 231-131-3
CAS number: 7440-22-4
results of the measured silver concentrations on days 7 and 28 -
transformation/dissolution of silver wire (massive) at 100 rpm at pH 8.
X ± S (µg/L)
0.03 ± 0.07
The Transformation/Dissolution of silver wire (massive) at pH 8 was
determined following OECD guideline 29. Loading of 3, 9 and 27 mg/L Ag
surface equivalent were exposed to aqueous test medium for 28 days and
the dissolved silver concentration was determined by ICP-MS analysis.
Conventional water solubility testing is not appropriate for sparingly
soluble metals and metal compounds (ECHA Guidance on information
requirements and Chemical Safety Assessment. Chapter R.7a: Endpoint
specific guidance. Version 2.1, August 2013). Therefore, Transformation
/ Dissolution (T/D) testing (OECD Series on testing and assessment No.
29) was conducted for silver massive.
Initial studies to determine the T/D behaviour of silver in
massive form (ECTX 2010b), which were performed using an epoxy resin
carrier to control the exposed surface area of silver during the test,
indicated unusual dissolution/solubility behaviour. Dissolved silver
concentrations increased rapidly, but then declined to a steady state
concentration. Further experimentation suggested that epoxy resin could
act as an adsorbent phase for silver, which would result in the decline
in the dissolved silver concentrations observed. It was further
hypothesised that during preparation of the test item minute particles
of silver may have become embedded in the epoxy vehicle, considerably
increasing the exposed surface area during the test. Given these
complications further experiments were proposed using a quartz glass
To address the limitations of the 2010 study, a further
“definitive test” on massive silver was performed using a quartz glass
vehicle to control the available surface area to a “surface equivalent”
of 3, 9, and 27 mg l-1(ECTX 2013). This study was conducted
at pH 8 only (based on the results of silver powder T/D testing) and
used fluorinated ethylene propylene vessels to minimise adsorption of
silver to the test system during the course of the 28 days test. The
test items were also cleaned ultrasonically prior to the start of the
exposure to remove residual particles of silver from the surface of the
quartz glass tubes remaining from sample preparation. The average blank
corrected dissolved silver concentrations in the test medium after 28
days exposure were below the analytical limit of detection of 0.02 µg l-1at
loading rates of 3 and 9 mg l-1, and was 0.03 (+/- 0.07) µg l-1at
a loading rate of 27 mg l-1.
According to a reliable factual database (Gestis), silver metal is
considered as practically insoluble.
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