Silver

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Series on Testing and Assessment No. 29 (23-Jul-2001): Guidance document on transformation/dissolution of metals and metal compounds in aqueous media

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

With the exception of the ICP-MS and TOC analysis

Type of method:

other: Transformation/dissolution

Specific details on test material used for the study:

Silver wire (massive)

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.02 µg/L

Element analysed:

silver

Loading of aqueous phase:

3 mg/L

Incubation duration:

7 d

Test conditions:

pH 8

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.02 µg/L

Element analysed:

silver

Loading of aqueous phase:

9 mg/L

Incubation duration:

7 d

Test conditions:

pH 8

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.02 µg/L

Element analysed:

silver

Loading of aqueous phase:

27 mg/L

Incubation duration:

7 d

Test conditions:

pH 8

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.02 µg/L

Element analysed:

silver

Loading of aqueous phase:

3 mg/L

Incubation duration:

28 d

Test conditions:

pH 8

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.02 µg/L

Element analysed:

silver

Loading of aqueous phase:

9 mg/L

Incubation duration:

28 d

Test conditions:

pH 8

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.03 µg/L

Element analysed:

silver

Loading of aqueous phase:

27 mg/L

Incubation duration:

28 d

Test conditions:

pH 8

Summarised results of the measured silver concentrations on days 7 and 28 - transformation/dissolution of silver wire (massive) at 100 rpm at pH 8.

 

	7 d		28 d
Loading (mg/L)	X ± S (µg/L)	CV (%)	X ± S (µg/L)	CV (%)
3	<0.02	-	<0.02	-
9	<0.02	-	<0.02	-
27	<0.02	-	0.03 ± 0.07	237

Conclusions:

Concentrations of silver were below or close to the detection limit of 0.02 μg/L Ag during the 28 days at pH 8 of the test for surface equivalent loading of 3 and 9 mg/L silver wire (massive) as well as the second two replicates with surface equivalent loading of 27 mg/L. However, a steady increase of dissolved silver concentration could be observed in the first replicate during the last three weeks of testing (average of 0.11 ± 0.01 μg/L Ag, CV: 6%).

Executive summary:

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.

Reference 2

Endpoint:

water solubility

Type of information:

other: Secondary literature

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: secondary literature, online database with authoritative values

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline followed

Principles of method if other than guideline:

Not applicable: secondary literature, online database with authoritative values.

GLP compliance:

no

Type of method:

other: no data

Remarks on result:

other: Reliable data from a factual database states that silver metal is practically insoluble. A figure for solubility cannot be given.

Details on results:

practically insoluble

Conclusions:

Interpretation of results: insoluble (< 0.1 mg/L)

Description of key information

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 vehicle.

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.

Key value for chemical safety assessment

Water solubility:

0.03 µg/L

at the temperature of:

20 °C

Additional information

According to a reliable factual database (Gestis), silver metal is considered as practically insoluble.