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Water solubility

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Reference
Endpoint:
transformation / dissolution of metals and inorganic metal compounds
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2016-09-07 to 2017-01-10
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
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:
no
Type of method:
flask method
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Element analysed:
Chromium
Loading of aqueous phase:
1 mg/L
Incubation duration:
7 d
Test conditions:
pH 6
Remarks on result:
not determinable because of methodological limitations
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Element analysed:
Chromium
Loading of aqueous phase:
1 mg/L
Incubation duration:
28 d
Test conditions:
pH 6
Remarks on result:
not determinable because of methodological limitations
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Element analysed:
Chromium
Loading of aqueous phase:
10 mg/L
Incubation duration:
7 d
Test conditions:
pH 6
Remarks on result:
not determinable because of methodological limitations
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
2.6 µg/L
Element analysed:
Chromium
Loading of aqueous phase:
100 mg/L
Incubation duration:
7 d
Test conditions:
pH 6
Remarks on result:
other: CV: 3%

A screening test to determine the pH of maximum dissolution between 6, 7 and 8 was performed for the chromium compound. The results correspond to the metal release after 24 hours of incubation at 22 °C with 200 rpm agitation rate and a mass loading of 100 mg/L. The data of metals released from the transformation / dissolution assays, is shown with the blanks information on the top half of the table and the samples information in the bottom half of the table. Mean: is the average metal release µg/L; St. Dev.: Standard deviation. CV, %: Coefficient of variation (ratio of Standard deviation respect to the mean concentration, in percentage).BDL: Below detection limit.

Chromium, µg/L
Screening pH 6
  Time [h] T [°C] O2[mg/L] pH Mean SD CV [%]
Blanks 0 21.9 6.6 6.03 BDL - -
24 22.5 6.6 6.11 BDL - -
CrB2 0 21.9 6.6 6.03 BDL - -
24 22.9 6.7 6.06 2.5 0.15 6
Screening pH 7
  Time [h] T [°C] O2[mg/L] pH Mean SD CV [%]
Blanks 0 21.0 7.1 7.08 BDL - -
24 21.7 7.0 7.05 BDL - -
 CrB2 0 21.0 7.1 7.08 BDL - -
24 21.5 7.0 7.03 1.2 0.21 18
Screening pH 8
  Time [h] T [°C] O2[mg/L] pH Mean SD CV [%]
Blanks 0 21.2 7.0 7.90 BDL - -
24 21.2 7.1 7.91 BDL - -
 CrB2 0 21.2 7.0 7.90 BDL - -
24 21.5 7.5 7.92 BDL - -

Very low solubility values were measured in the screening test for Chromium diboride. Values below or close to the method detection limit (MDL = 0.2 µg/L at pH 6, 7 and 8) and below the practical quantitation level (PQL = 1.0 – 1.2 for pH 6,7 and 8) are reported. Value between quotes are regarded as outliers and are not considered in the calculations.

Conclusions:
The results showed that chromium diboride can be considered as insoluble (< 0.1 mg/L) in aquoeus solution in this study according to OECD 29.
Executive summary:

A transformation/dissolution (T/D) test, according to OECD 29, was carried out to study the potential of chromium diboride to release metal to the environment.

A 24 hour screening test to determine the pH of maximum chromium release was performed at pH 6, 7 and 8 with a loading rate of 100 mg/l. The pH screening test showed niobium releases of 2.5 ± 0.15 µg Cr/L at pH 6, while the release of Cr at pH 7 and 8 was below the method detection limit.

The full T/D test was conducted at pH 6. The acute endpoint (7 days), was performed at sample loadings of 1, 10 and 100 mg/L; the chronic endpoint was determined from the extension of the 1 mg/L loading test to 28 days. The results of the study documented chromium release measurements as follows:

- 1 mg/l loading after 7 days: below detection limit

- 1 mg/l loading after 28 days: below dection limit          

- 10 mg/L loading after 7 days: below detection limit, and

- 100 mg/L loading after 7 days: 2.6 ± 0.07 μg Cr/L.

Therefore, chromium diboride is considered to be highly insoluble in water.

Description of key information

A transformation/dissolution (T/D) test was carried out, according to OECD Series on Testing and Assessment No 29 (2001): Transformation dissolution of metals and metal compounds in aqueous media, to study the potential of Chromium diboride to release metal ions to the environment. The test results are showing that the test substance is highly insoluble (< 0.1 mg/L).

Key value for chemical safety assessment

Water solubility:
2.6 µg/L
at the temperature of:
22.7 °C

Additional information

A transformation/dissolution (T/D) test, according to OECD 29, was carried out to study the potential of Chromium diboride to release metal to the environment. A 24 hours screening test to determine the pH of maximum Chromium release was performed at pH 6, 7 and 8 with a loading rate of 100 mg/L. The pH screening test showed Chromium releases of 2.5 ± 0.15 µg Cr/L at pH 6, while the release of Cr at pH 7 and 8 was below the method detection limit.

The full T/D test was conducted at pH 6. The acute endpoint (7 days), was performed at sample loadings of 1, 10 and 100 mg/L; the chronic endpoint was determined from the extension of the 1 mg/L loading test to 28 days. The results of the study documented Chromium release measurements as follows:

- 1 mg/L loading after 7 days: below detection limit

- 1 mg/L loading after 28 days: below dection limit          

- 10 mg/L loading after 7 days: below detection limit, and

- 100 mg/L loading after 7 days: 2.6 ± 0.07 μg Cr/L.

Therefore, chromium diboride is considered to be highly insoluble in water.