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Water solubility

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Reference
Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2016-04-11 to 2016-10-26
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
equivalent or similar to guideline
Guideline:
EU Method A.6 (Water Solubility)
Deviations:
no
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
flask method
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Colour and appearance: Colourless solid
- Batch: C14-193
- Purity: 100% (w/w)
- Expiry date: 15 Dec 2016

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: ambient: (+5 to +30 °C), dark, dry



Key result
Water solubility:
<= 2 925 µg/L
Conc. based on:
other: Lutetium
Incubation duration:
864 h
Temp.:
20 °C
pH:
6.14
Key result
Water solubility:
<= 115 µg/L
Conc. based on:
other: Yttrium
Incubation duration:
864 h
Temp.:
20 °C
pH:
6.14
Key result
Water solubility:
<= 0.823 µg/L
Conc. based on:
other: Cerium
Incubation duration:
864 h
Temp.:
20 °C
pH:
6.14
Key result
Water solubility:
<= 0.218 mg/L
Conc. based on:
other: Silicon
Incubation duration:
864 h
Temp.:
20 °C
pH:
6.14
Details on results:
The results for lutetium differ between the two bottles due to inhomogeneity of the test item. No mean solubility was calculated but the results of the two bottles were reported separately. The maximum solubility for each bottle which was determined is reported as result of the study. For silicon, cerium and yttrium the maximum mean is reported as result of the study.

The results of the preliminary test are presented in Table 1.

Table 1: Preliminary test in ultra-pure water at 20 °C

Test item [mg] Added volume of water [mL] Time of shaking [h] Remarks Approx.solubility [g/L]
10.9 1000 168 undissolved < 0.0109

The main test was performed in carbon dioxide saturated ultra-pure water. Tables 2 -5 show the results of the samples.

Table 2: Time course of the water solubility of lutetium in the test item at 20 °C and pH 5.97

Time [h] Sample no. Determined concentration of lutetium [µg/L] Mean concentration of lutetium [µg/L] pH
24 1
2
333
298
316 5.95
192 1
2
977
1003
990 5.95
312 1
2
1181
1158
1170 5.92
384 1
2
1330
1434
1382 5.98
552 1
2
1536
1485
1511 5.93
696 1
2
1629
1575
1602 5.95
864 1
2
2925*
2052*
2489 6.14
Mean: 5.97

* As the results of the individual determinations differ that much, not the mean will be reported, but the individual results.

Table 3: Time course of water solubility of cerium in the test item at 20 °C and pH 5.97

Time [h] Sample no. Determined concentration of cerium [µg/L] Mean concentration of cerium [µg/L] pH
24 1
2
0.149
0.176
0.163 5.95
192 1
2
0.469
0.493
0.481 5.95
312 1
2
0.566
0.578
0.572 5.92
384 1
2
0.639
0.661
0.650 5.98
552 1
2
0.699
0.702
0.701 5.93
696 1
2
0.800
0.758
0.779 5.95
864 1
2
0.834
0.812
0.823 6.14
Mean: 5.97

Table 4: Time course of the water solubility of yttrium in the test item at 20 °C and pH 5.97

Time [h] Sample no. Determined concentration of yttrium [µg/L] Mean concentration of yttrium [µg/L] pH
24 1
2
23.4
25.8
24.6 5.95
192 1
2
65.5
68.6
67.1 5.95
312 1
2
80.1
85.5
82.8 5.92
384 1
2
91.6
93.9
92.8 5.98
552 1
2
103
99.5
101 5.93
696 1
2
114
104
109 5.95
864 1
2
117
113
115 6.14
Mean: 5.97

Table 5: Time course of the water solubility of silicon in the test item at 20 °C and pH 5.97

Time [h] Sample no. Determined concentration of silicon [mg/L] Mean concentration of silicon [mg/L] pH
24 1
2
n.d.
n.d.
n.d. 5.95
192 1
2
0.134
0.140
0.137 5.95
312 1
2
0.156
0.160
0.158 5.92
384 1
2
0.170
0.161
0.166 5.98
552 1
2
0.205
0.203
0.204 5.93
696 1
2
0.210
0.205
0.208 5.95
864 1
2
0.215
0.221
0.218 6.14
Mean: 5.97

n.d. - not detected

According to OECD Guideline 105 it is considered to use the column elution method for water solubilities below 10-2 g/L. On the other hand the idea of the column elution method is to increase the surface of the test item to improve the contact with the eluent. This is mostly applicable for organic compounds. In case of inorganic metal powder there is no increasing of the surface by using the column elution method, so the flask method was used.

Conclusions:
The water solubility of the test item was determined in ultra-pure water at 20 °C:
Lutetium: ≤ 2925 µg/L / 2052 µg/L
Yttrium: ≤ 115 µg/L
Cerium: ≤ 0.823 µg/L
Silicon: ≤ 0.218 mg/L
Executive summary:

The water solubility of the test item was determined in ultra-pure water at 20 °C in adaption to EC method A.6 and OECD guideline 105 by using the flask method. The results for lutetium differ between the two bottles due to inhomogeneity of the test item. No mean solubility was calculated but the results of the two bottles were reported separately. For silicon, cerium and yttrium the maximum mean is reported as study result:

Lutetium: ≤ 2925 µg/L / 2052 µg/L

Yttrium: ≤ 115 µg/L

Cerium: ≤ 0.823 µg/L

Silicon: ≤ 0.218 mg/L

Description of key information

The water solubility of the test item was determined in ultra-pure water at 20 °C in adaption to EC method A.6 and OECD guideline 105 by using the flask method. The results for lutetium differ between the two bottles due to inhomogeneity of the test item. No mean solubility was calculated but the results of the two bottles were reported separately. For silicon, cerium and yttrium the maximum mean is reported as study result:

Lutetium: ≤ 2925 µg/L / 2052 µg/L

Yttrium: ≤ 115 µg/L

Cerium: ≤ 0.823 µg/L

Silicon: ≤ 0.218 mg/L

Key value for chemical safety assessment

Additional information

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