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Water solubility

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Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012-03-22 to 2012-04-05
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 105 (Water Solubility)
Qualifier:
according to
Guideline:
EU Method A.6 (Water Solubility)
GLP compliance:
no
Type of method:
flask method
Water solubility:
1.7 mg/L
Temp.:
20 °C
pH:
>= 5.5 - <= 6.3
Remarks on result:
other: Mean value
Details on results:
ICP-MS method was used in this study to determine Tellurium concentrations.

Summary of the main tests

Main test

Concentration tellurium (g/L)

 

I (24 hours)

1.4 x 10 E-3

 

II (48 hours)

2.5 x 10 E-3

 

III 96 hours)

1.7 x 10 E-3

 

IV (168 hours)

1.4 x 10 E-3

 

Mean value

1.7 x 10 E-3

 

Standard deviation

0.0007

 

Conclusions:
Interpretation of results (migrated information): slightly soluble (0.1-100 mg/L)
In a study conducted according to OECD guideline 105 and EU method A6 the water solubility of tellurium powder was determined to be 1.7 mg/L at 20 °C using a modified flask method.
Executive summary:

In a study conducted according to OECD guideline 105 and EU method A6 the water solubility of tellurium powder was determined using a modified flask method. The study was performed under argon. The pH value was approx. 6.

For analytical determination the concentrations of Tellurium in the water extracts of the test item were measured by means of ICP-MS.

The mean solubility of tellurium powder was determined to be 1.7 mg/L at 20 °C.

Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012-04-13 to 2012-12-27
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
GLP compliance:
yes (incl. certificate)
Type of method:
flask method
Water solubility:
0.745 mg/L
Temp.:
21.4
pH:
6
Remarks on result:
other: Screening test; loading 100 mg/L; sampling time 24 hours; dissolved Te
Water solubility:
1.303 mg/L
Temp.:
21.4
pH:
8
Remarks on result:
other: Screening test; loading 100 mg/L; sampling time 24 hours; dissolved Te
Water solubility:
20.02 µg/L
Temp.:
21.2
pH:
8
Remarks on result:
other: Main test: loading 1 mg/L; sampling time 7 days; dissolved Te
Water solubility:
183.3 µg/L
Temp.:
21
pH:
8
Remarks on result:
other: Main test: loading 10mg/L; sampling time 7 days; dissolved Te
Water solubility:
1.762 mg/L
Temp.:
21
pH:
8
Remarks on result:
other: Main test: loading 100 mg/L; sampling time 7 days; dissolved Te
Details on results:
Main Test
At a loading of 1 mg/L dissolved tellurium concentrations after 28 days were at 59.64 ± 4.90 µg/L at pH 8. The observed variations within (< 10%) and between (< 20 %) the test flasks are in compliance with the guidance document.
Total dissolved tellurium concentrations in method blanks exhibited higher Te levels due to potential carryover from pH-electrode or oxygen sensor. Although the electrode and the oxygen sensor were rinsed extensively with ultrapure water before inserting into another vessel a contamination is observable. Therefore, the mean Te concentration per sampling in method blanks were additionally subtracted from the measurement results and the dissolved tellurium concentrations after 28 days were calculated to be 51.77 ± 4.90 µg/L at pH 8 .
At a loading of 10 mg/L dissolved tellurium concentrations after 7 days were at 183.3 ± 8.4 µg/L at pH 8 The observed variations within (< 10%) and between (< 20 %) the test flasks are in compliance with the guidance document.
At a loading of 100 mg/L dissolved tellurium concentrations after 7 days were at 1.762 ± 0.089 mg/L at pH 8. The observed variations within (< 10%) and between (< 20 %) the test flasks are in compliance with the guidance document.

Screening test:

Measured dissolved Te concentrations for the loading of 100 mg/L:

 

Sample

pH

Mean Te concentration

mg/L±SD

24 h

8

1.303 ± 0.035

24 h

6

0.7446 ± 0.0187

 

Main Test:

Measured dissolved Te concentrations for the loading of 1 mg/L:

Sample time

pH

mean Te conc.

all vessels ± SD

[μg/L]

between vessel

variation [%]

variations of mean Te conc. between sampling intervals [%]

2 h

8

10.87 ± 0.52

4.7

-

6 h

8

11.83 ± 0.63

5.3

8.9

24 h

8

18.49 ± 3.59

19.4

56.2

96 h (4d)

8

22.42 ± 2.12

9.4

21.3

168 h (7d)

8

28.11 ± 1.75

6.2

25.4

336 h (14d)

8

38.26 ± 2.02

5.3

36.1

504 h (21d)

8

49.92 ± 3.72

7.5

30.5

672 h (28d)

8

59.64 ± 4.90

8.2

19.5

 

Measured dissolved Te concentrations for the loading of 1 mg/L -mean Te concentrations in method blanks

Sample time

pH

mean Te conc.

all vessels ± SD

[μg/L]

between vessel

variation [%]

variations of mean Te conc. between sampling intervals [%]

2 h

8

10.60 ± 0.52

4.9

-

6 h

8

7.762 ± 0.631

8.1

-26.8

24 h

8

12.86 ± 3.59

27.9

65.7

96 h (4d)

8

15.52 ± 2.12

13.6

20.7

168 h (7d)

8

20.02 ± 1.75

8.7

29.0

336 h (14d)

8

30.19 ± 2.02

6.7

50.8

504 h (21d)

8

41.81 ± 3.72

8.9

38.5

672 h (28d)

8

51.77 ± 4.90

9.5

23.8

 

 

Measured dissolved Te concentrations for the loading of 10 mg/L

Sample time

pH

mean Te conc.

all vessels ± SD

[µg/L]

between vessel

variation [%]

variations of mean Te conc. between sampling intervals [%]

2 h

8

99.4 ± 6.5

6.5

-

6 h

8

113.7 ± 2.4

2.1

14.3

24 h

8

136.6 ± 4.5

3.3

20.2

96 h (4d)

8

154.8 ± 4.5

2.9

13.4

168 h (7d)

8

183.3 ± 8.4

4.6

18.4

 

 

Measured dissolved Te concentrations for the loading of 100 mg/L

Sample time

pH

mean Te conc.

all vessels ± SD

[mg/L]

between vessel

variation [%]

variations of mean Te conc. between sampling intervals [%]

2 h

8

0.6954 ± 0.0364

5.2

-

6 h

8

0.9905 ± 0.0431

4.3

42.4

24 h

8

1.273 ± 0.060

4.7

28.5

96 h (4d)

8

1.526 ± 0.062

4.1

19.9

168 h (7d)

8

1.762 ± 0.089

5.1

15.5

 

Conclusions:
Interpretation of results (migrated information): slightly soluble (0.1-100 mg/L)
For the transformation/dissolution test of tellurium a target pH of 8 was determined in a screening test at 21.5 °C. After 7 days Te concentrations were 20.02 µg/L, 183.3 µg/L and 1.762 mg/L at loadings of 1mg/L, 10 mg/L and 100 mg/L, respectively.
Executive summary:

A study was conducted to determine the transformation/dissolution of tellurium according to OECD guidance document 29 (2001). The test objective was to study the transformation & dissolution of the test item over 7 days with loadings of 1 mg/L, 10 mg/L and 100 mg/L.

The test with a loading of 1 mg/L was prolonged to 28 days.

Dissolved tellurium concentrations were determined by ICP-OES.

The OECD guidance document 29 requests the performance of the test at a pH which maximizes the dissolution. Therefore, prior to the full test a screening over 24 h (agitation at 100 rpm, 21.5 ± 1.5 °C, loadings of 100 mg/L) was conducted in test media at pH 6 and pH 8 in triplicate vessels and duplicate samples per vessel.

 

After 24 h the mean dissolved Te concentrations were 1.303 ± 0.035 mg/L and 0.7446 ± 0.0187 mg/L for pH 8 and 6, respectively. Based on these results the full test was performed in test media at a target pH of 8.

Solutions in the full test were sampled after 2h, 6h, 24h, 96h (4d), 168h (7d). For the test up to 28 days samples were additionally taken after 336h (14d), 504h (21d) and 672h (28d).

Solution pHs, oxygen concentrations and total dissolved tellurium concentrations were measured. The test was performed in triplicates (three replicates per pH treatment, sampled twice at each sampling point).

 

Final results:

At a loading of 1 mg/L dissolved tellurium concentrations after 28 days were at 59.64 ± 4.90 µg/L at pH 8.

Total dissolved tellurium concentrations in method blanks exhibited higher Te levels due to potential carryover from pH-electrode or oxygen sensor. Although the electrode and the oxygen sensor were rinsed extensively with ultrapure water before inserting into another vessel a contamination is observable. Therefore, the mean Te concentration per sampling in method blanks were additionally subtracted from the measurement results and the dissolved tellurium concentrations after 28 days were calculated to be 51.77 ± 4.90 µg/L at pH 8 .

At a loading of 10 mg/L dissolved tellurium concentrations after 7 days were at 183.3 ± 8.4 µg/L at pH 8.

At a loading of 100 mg/L dissolved tellurium concentrations after 7 days were at 1.762 ± 0.089 mg/L at pH 8.

The observed variations within (< 10%) and between (< 20 %) the test flasks are in compliance with the guidance document.

Description of key information

Data are available from a transformation dissolution test, conducted according to OECD guideline 29, and a water solubility study according to OECD guideline 105.  Both study data are reliable without restrictions. 

Key value for chemical safety assessment

Water solubility:
1.762 mg/L
at the temperature of:
21 °C

Additional information

In a study conducted according to OECD guideline 105 and EU method A6 the water solubility of tellurium powder was determined to be 1.7 mg/L at 20 °C using a modified flask method.

Transformation/dissolution study of tellurium according to OECD guidance document 29 (2001):

Screening test after 24 hours at 20.9 °C:

1.303 mg/L at pH 8

0.7446 mg/L at pH 6

Main test, sampling time 7 days, at pH 8 and 21 °C:

Loading 1 mg/L               20.02 µg/L

Loading 10 mg/L            183.3 µg/L 

Loading 100 mg/L        1.762 mg/L

Loading 1 mg/L/ 28 days sampling time:   59.64 µg/L  

The value of  1.762 mg/L is chosen for chemical safety assessment, as a worst case assumption.