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Physical & Chemical properties

Water solubility

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
13 July 2016 – 23 February 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method A.6 (Water Solubility)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
other: both flask and column elution methods were used
Water solubility:
2.1 g/L
Conc. based on:
element (dissolved fraction)
Remarks:
Gd
Incubation duration:
>= 24 - <= 72 h
Temp.:
20 °C
pH:
4
Remarks on result:
other: Flask method, mean of 24, 48 and 72 h
Water solubility:
2.5 g/L
Conc. based on:
test mat. (dissolved fraction)
Remarks:
Result calculated based on dissolved Gd measurements
Incubation duration:
>= 24 - <= 72 h
Temp.:
20 °C
pH:
4
Remarks on result:
other: Flask method, mean of 24, 48 and 72 h
Water solubility:
3.1 mg/L
Conc. based on:
element (dissolved fraction)
Remarks:
Gd
Temp.:
20 °C
pH:
6.4
Remarks on result:
other: Column elution method, mean of flow rates 12.5 mL/h and 25 mL/h
Water solubility:
3.5 mg/L
Conc. based on:
test mat. (dissolved fraction)
Remarks:
Result calculated based on dissolved Gd measurements
Temp.:
20 °C
pH:
6.4
Remarks on result:
other: Column elution method, mean of flow rates 12.5 mL/h and 25 mL/h
Key result
Water solubility:
0.5 mg/L
Conc. based on:
element (dissolved fraction)
Remarks:
Gd
Temp.:
20 °C
pH:
7
Remarks on result:
other: Column elution method, mean of flow rates 12.5 mL/h and 25 mL/h
Key result
Water solubility:
0.5 mg/L
Conc. based on:
test mat. (dissolved fraction)
Remarks:
Result calculated based on dissolved Gd measurements
Temp.:
20 °C
pH:
7
Remarks on result:
other: Column elution method, mean of flow rates 12.5 mL/h and 25 mL/h
Water solubility:
0.1 mg/L
Conc. based on:
element (dissolved fraction)
Remarks:
Gd
Temp.:
20 °C
pH:
9
Remarks on result:
other: Column elution method, mean of flow rates 12.5 mL/h and 25 mL/h
Water solubility:
0.1 mg/L
Conc. based on:
test mat. (dissolved fraction)
Remarks:
Result calculated based on dissolved Gd measurements
Temp.:
20 °C
pH:
9
Remarks on result:
other: Column elution method, mean of flow rates 12.5 mL/h and 25 mL/h
Details on results:
Results were validated by:
- Linearity validation: The analysis showed a good linearity of the method (r > 0.99)
- Accuracy validation: Results in dilution mixture showed a good accuracy which indicates acceptable data (recoveries ranged between 75 and 125%).
- Repeatability validation: The results indicated a good precision of the data.
- Specificity: The intensity (CPS) of blank samples measured was negligible or similar to solvent intensity.
- Limit of quantification: For the method in solution the LOQ was set at 1 ng/mL.

The individual results are shown in the tables below.

Flask method at pH 4  Incubation duration  Solubility as Gd content (mg/L)  Gd2O3 solubility (mg/L)
 Test 1  24 h  2167  2492
 Test 2  48 h  2156  2479
 Test 3  72 h  2099  2413
 Mean    2141  2461

 Column elution method at pH 6.4  Flow rate (mL/h)   Solubility as Gd content (mg/L)   Gd2O3 solubility (mg/L)
 Test 1  25  2.93  3.37
 Test 2  25  2.90  3.34
 Test 3  12.5  3.37  3.88
 Mean    3.1  3.5

Column elution method at pH 7  Flow rate (mL/h)   Solubility as Gd content (mg/L)   Gd2O3 solubility (mg/L)
 Test 1 (discarded)  25  0.34  0.39
 Test 2  25  0.41 0.47
 Test 3  12.5  0.51  0.59
 Mean    0.5  0.5

The results of test 1 were discarded to maintain a difference of < 30% between the results obtained at the 2 flow rates.

Column elution method at pH 9  Flow rate (mL/h)   Solubility as Gd content (mg/L)   Gd2O3 solubility (mg/L)
 Test 1 12.5  0.09  0.10
 Test 2 12.5  0.12  0.14
 Test 3 25  0.11  0.13
 Mean    0.1  0.1
Conclusions:
The water solubility (expressed as gadolinium oxide concentration) of the test substance was determined to be 2.5 g/L, and 3.5, 0.5 and 0.1 mg/L at pH 4, 6.4, 7 and 9, respectively, and was calculated from the measured gadolinium content in water which was 2.1 g/L at pH 4 (flask method), 3.1 mg/L at pH 6.4, 0.5 mg/L at pH 7 and 0.1 mg/L at pH 9 (column elution method). Results of this study can be considered reliable without restriction.

Description of key information

In a GLP study (Klimisch 1, Jean-Baptiste, 2017) based on the OECD 105 and EC A.6 test guidelines, the water solubility of gadolinium oxide was determined to be 2.5 g/L at pH 4, 3.5 mg/L at pH 6.4, 0.5 mg/L at pH 7 and 0.1 mg/L at pH 9, expressed as gadolinium oxide content in water at 20°C and extrapolated from the measured values of dissolved gadolinium which were 2.1 g/L at pH 4, 3.1 mg/L at pH 6.4, 0.5 mg/L at pH 7 and 0.1 mg/L at pH 9.

This study was assigned as key study.

Key value for chemical safety assessment

Water solubility:
0.5 mg/L
at the temperature of:
20 °C

Additional information