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Endpoint:
transformation / dissolution of metals and inorganic metal compounds
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
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:
yes
Remarks:
Determination at pH 6 and 8 instead of 5.5 and 8.5
GLP compliance:
no
Type of method:
other: transformation/dissolution
Test material information:
Composition 1
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
246.77 µg/L
Element analysed:
Zn
Loading of aqueous phase:
1 other: mg test item / L
Incubation duration:
24 h
Test conditions:
pH 6
Remarks on result:
other: SD: 29.30 µg/L
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
187.46 µg/L
Element analysed:
Zn
Loading of aqueous phase:
1 other: mg test item / L
Incubation duration:
7 d
Test conditions:
pH 6
Remarks on result:
other: SD: 2.88 µg/L
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
163.92 µg/L
Element analysed:
Zn
Loading of aqueous phase:
1 other: mg test item / L
Incubation duration:
28 d
Test conditions:
pH 6
Remarks on result:
other: SD: 5.45 µg/L
Details on results:
Temperature
The temperature of the thermostatically controlled room was recorded with a Testo 175-T2 data logger. The mean temperature was 21.0 ± 0.1 °C during the 24 h screening test with 100 mg/L loading at pH 6 and 8. In the full test the mean temperatures were 21.8 ± 0.2 °C for 10 and 100 mg/L loading (168 h test duration) and 21.6 ± 0.3 °C for 1 mg/L loading (672 h test duration). Therefore, the mean temperature is in agreement with the OECD guidance document 29.

Solution pH and oxygen concentrations
The pH values in screening test (loading 100 mg/L) at pH 8 and 6 remained relatively stable in method blanks and test item loaded vessels in the range of 7.7 – 7.9 and 5.9 – 6.2, respectively. The pH in method blanks in full test remained relatively stable in the range of 5.9 – 6.2. The pH in 1 mg test item/L loaded vessels were in the range of 5.9 – 6.4 during test. The pH in 10 mg test item/L loaded vessels were in the range of 6.0 – 6.4 during test. The pH in 100 mg test item/L loaded vessels increased from 5.9, 6.0 up to 6.5.
Oxygen levels of all test solutions (all loadings) were in the range recommended by the OECD Test Guidance 29 during the test: above 70 % of oxygen saturation at 8.5 mg/L (70 % of 8.5 mg/L = 6 mg/L = 6 ppm).

Analytical measurements of inorganic Zn
Method blanks were mostly above respective LOQs but below concentrations in respective samples (< 4.7 %)
The OECD Series 29 requires a limit of 20 % and 10 % for the between-vessel and the within-vessel variation, respectively.
The observed variations within and between test item loaded vessels are mostly in compliance with the test guideline, except within-vessel variations at the loading of 10 mg/L (full test) after 6h (vessel 4: 11.3 %) and after 24 h (vessel 6: 12.8 %).
According to OECD Test Guidance 29, “[…]it is reasonable to anticipate that for a constant loading of a substance, tested in a narrow particle size (e.g. 37 - 44 μm) and total surface area range, the within-vessel variation in transformation data should be less than 10 % and the between-vessel variation should be less than 20 %”. Moreover, the particle size distribution of each loading replicate may differ and thus resulting in different overall total surface areas per vessel. Since the exposed surface area is affecting the rate of transformation and dissolution of sparingly soluble metal compounds, increases in between-vessel variations may be observed in tests of materials with wider particle size distributions.
Moreover, increased within vessel variations may hint at formation of colloidal Zn species, which are smaller than 0.2 µm (applied filter) and may be distributed inhomogenously.
According to OECD Test Guidance 29, the equilibrium had been established in the full test with loadings of 1 and 10 mg/L because “ […] three subsequent total dissolved metal concentration data points vary no more than 15%”.

Mass balance
Zinc recoveries for the full test with 1 mg/L ranged from of 92.1 to 102.6 %. Recoveries for 10 mg/L were in the range of 96.0 – 98.0 % and for 100 mg/L within 102.8 – 107.9 %. Recoveries for the loading of 100 mg/L are still within the QA/QC requirements but quite low. This is probably due to residues in the filters used for sampling.

Method validation summary (ICP-OES)

validation parameter

results

Comment

selectivity

selective wavelengths 206.200 nm

no interferences observed

linearity

applied calibration functions were linear

correlation factor at least 0.999930

limit of detection

screening test: 0.4492 µg Zn/L

full test: 0.065 – 0.2887 µg Zn/L

mass balance: 0.4177 µg Zn/L

limit of quantification

screening test: 1.3476 µg Zn/L

full test: 0.1945 – 0.8662 µg Zn/L

mass balance: 0.4177 µg Zn/L

accuracy and precision

mean recovery for certified reference material TM 26.4:

screening test: 103.0 ± 1.5 % (n = 4)

mass balance: 109.1 ± 0.9 % (n = 3)

certified with 38.0 µg Zn/L

accuracy and precision, repeatability

mean recovery for certified reference material TM 26.4:

full test: 101.8 ± 1.2 % (n = 8)

certified with 38.0 µg Zn/L

accuracy and precision

mean recovery for quality control standard – 19 elements:

screening: 101.5 ± 0.7 % (n = 4)

diluted to 50 µg Zn/L

accuracy and precision

mean recovery for multi element standard XXI:

screening test: 105.1 ± 0.7 % (n = 4)

mass balance: 98.7 ± 0.4 % (n = 3)

diluted to 100 µg Zn/L

accuracy and precision, repeatability

mean recovery for multi element standard XXI:

full test: 99.0 ± 1.5 % (n = 10)

diluted to 100 µg Zn/L

accuracy and precision

mean recovery for recalibration standard:

mass balance: 100.6 ± 0.6 % (n = 3)

diluted to 50 µg Zn/L

accuracy and precision, repeatability

mean recovery recalibration standard:

full test: 98.4 ± 0.6 % (n = 10)

diluted to 50 µg Zn/L

Trueness

Recoveries of fortified samples:

Screening test: 105.4 % (n = 1)

Full test: 98.9 % - 114.5 % (n = 8)

Mass balance: 101.7 % and 104.2 % (n = 2)

Sample fortification and calculation of recoveries

sample name

measured conc.

[µg Zn/L]

nominal conc. after fortification

[µg Zn/L]

recovery

[µg Zn/L] / [%]

Screening test: 4 mL of sample + 1 mL of 400 µg Zn/L

Vessel 4 sample a after 24 h (dilution factor 100)

97.87

158.30

166.81 / 105.4

Full test: 4 mL of sample + 1 mL of 80 µg Zn/L

Vessel 4 sample a after 2 h (dilution factor 10, loading 1 mg/L)

 24.28

35.43

35.02 / 98.9

Vessel 4 sample a after 6 h (dilution factor 10, loading 1 mg/L)

 23.29

34.63

35.69 / 103.1

Vessel 4 sample a after 24 h (dilution factor 10, loading 1 mg/L)

 26.89

37.51

37.09 / 98.9

Vessel 4 sample a after 96 h (dilution factor 10, loading 1 mg/L)  

 19.90

31.92

36.56 / 114.5

Vessel 4 sample a after 168 h (dilution factor 10, loading 1 mg/L)

 19.12

31.29

31.94 / 102.1

Vessel 4 sample a after 336 h (dilution factor 10, loading 1 mg/L)  

 19.10

31.28

31.53 / 100.8

Vessel 4 sample a after 504 h (dilution factor 10, loading 1 mg/L)

 18.28

30.63

33.11 / 108.1

Vessel 4 sample a after 672 h (dilution factor 10, loading 1 mg/L)

17.61

30.09

31.40 / 104.4

Mass balance: 4 mL of sample + 1 mL of 40 µg Zn/L

Vessel 6 (loading 100 mg/L)

17.34

21.87

22.79 / 104.2

Filter 6 (loading 100 mg/L)

30.88

32.70

33.26 / 101.7

Results of inorganic analysis

Test

Zn concentration

Remarks

Screening

test (loading of 100 mg/L, 24 h)

10.12 ± 0.53 mg/L at pH 8

23.40 ± 0.07 mg/L at pH 6

 

Full test

(loading of 1 mg/L, 24 h)

246.77 ± 29.30 µg/L at pH 6

According to OECD Series 29, an equilibrium had been reached after 96 h because “[…] three subsequent total dissolved metal concentration data points vary no more than 15 %.” After 96 h to 672 h of testing the equilibrium remained. The observed variations within and between test vessels are in compliance with the test guideline*, except within-vessel variation after 96 h (vessel 6: 11.0 %).

Full test

(loading of 1 mg/L, 168 h)

187.46 ± 2.88 µg/L at pH 6

Full test

(loading of 1 mg/L, 672 h)

163.92 ± 5.42 µg/L at pH 6

Full test

(loading of 10 mg/L, 24 h)

2400.87 ± 123.34 µg/L at pH 6

According to OECD Series 29, an equilibrium had been reached after 24 h because “[…] three subsequent total dissolved metal concentration data points vary no more than 15 %.” The observed variations within and between test vessels are in compliance with the test guideline*, except within vessel variations after 6 h (vessel 4: 11.3 %) and after 24 h (vessel 6: 12.8 %).

Full test

(loading of 10 mg/L, 168 h)

1890.63 ± 34.84 µg/L at pH 6

Full test

(loading of 100 mg/L, 24 h)

23407.75 ±109.80 µg/L at pH 6

According to OECD Series 29, an equilibrium had been reached after 24 h because “[…] three subsequent total dissolved metal concentration data points vary no more than 15%.”The observed variations within and between test vessels are in compliance with the test guideline*.

Full test

(loading of 100 mg/L, 168 h)

19635.85 ± 311.05 µg/L at pH 6

*The OECD Series 29 requires a limit of 20 % and 10 % for the between-vessel and the within-vessel variation, respectively.

Results of organic analysis

Test

Mean dissolved

5-nitroisophthalic acid

Remarks

Screening test

(loading of 100 mg/L, 24 h)

71.037 ± 0.016 mg /L at pH 6,

63.623 ± 0.04 mg /L at pH 8

 

Full test

(loading of 1 mg/L, 24 h)

0.750 ± 0 001 mg/L at pH 6

According to OECD Series 29, an equilibriumhad beenreached after 336 h because “[…] three subsequent total dissolved metal concentration data points vary no more than 15 %.” After 672 h of testing the equilibrium remained. The observed variations within and between test vessels are in compliance with the test guideline*.

Full test

(loading of 1 mg/L, 168h)

0.633 ± 0.010 mg/L at pH 6

Full test

(loading of 1 mg/L, 672 h)

0.575 ± 0.001 mg/L at pH 6

Full test

(loading of 10 mg/L, 24 h)

7.731 ± 0.064 mg/L at pH 6

A decrease of 16.97 % of dissolved 5-nitroisophthalic acid were observed from 24 h to 168 h of testing. The observed variations within and between test vessels are in compliance with the test guideline*.

Full test

(loading of 10 mg/L, 168 h)

6.419 ± 0.025 mg/L at pH 6

Full test

(loading of 100 mg/L, 24 h)

76.360 ± 0.061 mg/L at pH 6

A decrease of 14.42 % of dissolved 5-nitroisophthalic acid were observed from 24 h to 168 h of testing. The observed variations within and between test vessels are in compliance with the test guideline*.

Full test

(loading of 100 mg/L, 168 h)

65.345 ± 0.831 mg/L at pH 6

*The OECD Series 29 requires a limit of 20 % and 10 % for the between-vessel and the within-vessel variation, respectively.

The analytical result of the blank sample was < LOQ.

Mass balance

Zinc recoveries for the full test with 1 mg/L ranged from of 92.1 to 102.6 %. Recoveries for 10 mg/L were in the range of 96.0 – 98.0 % and for 100 mg/L within 102.8 – 107.9 %. Recoveries for the loading of 100 mg/L are still within the QA/QC requirements but quite low. This is probably due to residues in the filters used for sampling.

Calculation of mass balances

vessel

mass of Zn in samples

[µg]

mass of Zn in rinsed filters

[µg]

mass of Zn in vessels after test end and addition ofaqua regia

[µg]

total mass Zn
[µg]

added test item to vessels

[µg]

amount of Zn in test item

[µg]

Zn recovery [%]

1 mg/L 

4 pH6

85.21

0.48

173.40

259.09

1014

252.59

102.6

5 pH6

78.68

0.61

154.96

234.25

1009

251.34

93.2

6 pH6

59.53

0.53

171.43

231.50

1009

251.34

92.1

10 mg/L

4 pH6

538.95

2.85

1852.45

2394.25

10005

2492.25

96.1

5 pH6

534.07

3.05

1904.82

2441.94

10008

2492.99

98.0

6 pH6

458.10

2.82

1934.28

2395.20

10014

2494.49

96.0

100 mg/L

4 pH6

5342.52

30.94

20243.04

25616.50

100031

24917.72

102.8

5 pH6

5378.98

28.77

21465.96

26873.72

100001

24910.25

107.9

6 pH6

4501.63

24.70

21869.54

26395.87

100009

24912.24

106.0

Conclusions:
According to the OECD Series on Testing and Assessment Number 29 (2001), dissolved mean Zn concentrations were determined in a transformation/dissolution test with a loading of 1 mg test item (zinc 5-nitroisophthalate) /L media (agitation at 100 rpm, 21.5 ± 1.5 °C) over 672 hours with samplings after 2 h, 6 h, 24 h, 96 h, 168 h, 332 h, 504 h and 672 h.
Following Zn concentrations were determined at pH 6:
- 246.77 ± 29.30 µg/L after 24 h
- 187.46 ± 2.88 µg/L after 168 h
- 163.92 ± 5.42 µg/L after 672 h
The following zinc 5-nitroisophthalate concentrations were calculated on the basis of the molecular formula and a corresponding Zn content of 24.91 %:
- 990.65 ± 117.62 µg/L after 24 h
- 752.55 ± 11.56 µg/L after 168 h
- 658.05 ± 21.76 µg/L after 672 h
Endpoint:
transformation / dissolution of metals and inorganic metal compounds
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
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:
yes
Remarks:
Determination at pH 8 instead of 5.5 and 8.5
GLP compliance:
no
Type of method:
other: transformation/dissolution
Test material information:
Composition 1
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
212.64 µg/L
Element analysed:
Zn
Loading of aqueous phase:
1 other: mg test item / L
Incubation duration:
24 h
Test conditions:
pH 8
Remarks on result:
other: SD: 5.09 µg/L
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
204.67 µg/L
Element analysed:
Zn
Loading of aqueous phase:
1 other: mg test item / L
Incubation duration:
7 d
Test conditions:
pH 8
Remarks on result:
other: SD: 9.72 µg/L
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
218.59 µg/L
Element analysed:
Zn
Loading of aqueous phase:
1 other: mg test item / L
Incubation duration:
28 d
Test conditions:
pH 8
Remarks on result:
other: SD: 23.03 µg/L
Details on results:
Temperature
The temperature of the thermostatically controlled room was recorded with a Testo 175-T2 data logger. The mean temperature was 21.3 ± 0.2 °C during the 672 h test with 1 mg/L loading at pH 8. Therefore, the mean temperature is in agreement with the OECD guidance document 29.

Solution pH and oxygen concentrations
The pH in test item loaded vessels and method blanks ranged from 7.7 to 8.0.
Oxygen levels of all test solutions (all loadings) were in the range recommended by the OECD Test Guidance 29 during the test: above 70 % of oxygen saturation at 8.5 mg/L (70 % of 8.5 mg/L = 6 mg/L = 6 ppm)

Analytical measurements of inorganic Zn
Method blanks after 168 and 672 h were above respective LOQs but far below concentrations in actual samples (< 1.5 %).
The OECD Series 29 requires a limit of 20 % and 10 % for the between-vessel and the within-vessel variation, respectively. The observed variations within and between test item loaded vessels are in compliance with the test guidance.
According to the OECD 29 the equilibrium had been established in the full test because “ […] three subsequent total dissolved metal concentration data points vary no more than 15%”

Mass balance
Zinc recoveries for the test with 1 mg/L at pH8 ranged from 88.0 to 96.0 %.

Method validation summary (ICP-OES)

validation parameter

results

Comment

selectivity

selective wavelengths of 213.857 nm

no interferences observed

linearity

applied calibration functions were linear

correlation factor at least 0.998735

limit of detection

1 mg/L test: 0.199 – 0.624 µg Zn/L

mass balance: 0.067 µg Zn/L

limit of quantification

1 mg/L test: 0.596 – 1.872 µg Zn/L

mass balance: 0.202 µg Zn/L

Mehod blanks

Method blanks from 168 and 672 h slightly above respective LOQs, but far below conc. in actual samples.

 

accuracy and precision, repeatability

mean recovery for certified reference material TM 26.4:

1 mg/L test: 110.1 ± 3.4 % (n = 9)

mass balance: 106.8 ± 0.4 % (n = 3)

certified with 38.0 µg Zn/L

accuracy and precision, repeatability

mean recovery for multi element standard XXI:

1 mg/L test: 103.6 ± 3.2 % (n = 9)

mass balance: 98.9 ± 1.3 % (n = 3)

diluted to 100 µg Zn/L

accuracy and precision, repeatability

mean recovery for recalibration samples:

1 mg/L test: 104.2 ± 2.8 % (n = 9)

mass balance: 96.7 ± 1.3 % (n = 3)

diluted to 50 µg Zn/L

Trueness

Recoveries of fortified samples:

1 mg/L test: 101.6 – 102.0 % (n = 3)

Sample fortification and calculation of recoveries

sample name

measured conc.
[µg Zn/L]

nominal conc. after
fortification
[µg Zn/L]

recovery
[µg Zn/L] / [%]

4 mL of sample + 1 mL of 400 µg Zn/L

Vessel 1 sample a after 24h

231.52

250.81

255.94 / 102.0

Vessel 1 sample a after 168h
(dilution factor 2)

105.88

164.70

167.38 / 101.6

1 mL of sample + 4 mL of 80 µg Zn/L

Vessel 1 sample a after 672h
(dilution factor 20)

11.43

25.14

26.55 / 105.6

Results of inorganic analysis

Zn concentrations in test with loading of 1 mg/L at pH 8 (1,2,3 – triplicate vessels pH8; a,b – duplicate samples)

vessel and sample

dilution factor

measured Zn 213.857 [µg/L]

measured*dilution Zn conc. [µg/L]

mean Zn conc. per vessel [µg/L]

SD Zn conc. per vessel [µg/L]

within vessel variation [%]

mean Zn conc. all vessels [µg/L]

SD Zn conc. all vessels [µg/L]

between vessel variation [%]

variation between sampling intervals [%]

1a 24h

1

213.52

213.52

1b 24h

1

217.39

217.39

215.45

2.74

1.3

2a 24h

1

215.32

215.32

2b 24h

1

216.06

216.06

215.69

0.52

0.2

3a 24h

1

205.24

205.24

3b 24h

1

208.29

208.29

206.77

2.16

1.0

212.64

5.09

2.4

1a 168h

2

105.88

211.76

1b 168h

2

105.29

210.57

211.16

0.84

0.4

2a 168h

2

105.07

210.13

2b 168h

2

104.29

208.58

209.36

1.10

0.5

3a 168h

2

96.78

193.56

3b 168h

2

96.72

193.43

193.50

0.09

0.0

204.67

9.72

4.7

-3.7

1a 672h

20

11.427

228.54

1b 672h

20

11.204

224.08

226.31

3.15

1.4

2a 672h

20

11.2239

224.48

2b 672h

20

12.4527

249.05

236.77

17.38

7.3

3a 672h

20

9.68613

193.72

3b 672h

20

9.58219

191.64

192.68

1.47

0.8

218.59

23.03

10.5

6.8

Mass balance

Zinc recoveries for the test with 1 mg/L at pH8 ranged from 88.0 to 96.0 %.

Calculation of mass balances for the loading of 1 mg/L

vessel

mass of Zn in samples

[µg]

mass of Zn in vessels after test end and addition ofaqua regia
[µg]

mass of Zn from rinsed filter
[µg]

total mass Zn
[µg]

added test item to vessels

[µg]

Calculated
amount of Zn in test item
(24.91 %)

[µg]

Zn recovery [%]

 

1 mg/L

1 pH8

26.12

197.69

0.27

224.08

1022

254.56

88.0

2 pH8

26.47

195.14

0.24

221.85

1019

253.82

87.4

3 pH8

23.72

215.56

0.22

239.50

1002

249.58

96.0

Conclusions:
According to the OECD Series on Testing and Assessment Number 29 (2001), dissolved mean Zn concentrations were determined in a transformation/dissolution test with a loading of 1 mg test item (zinc 5-nitroisophthalate) /L media (agitation at 100 rpm, 21.5 ± 1.5 °C) over 672 hours with samplings after 24 h, 168 h and 672 h.
Following Zn concentrations were determined at pH 8:
- 212.64 ± 5.09 µg/L after 24 h
- 204.67 ± 9.72 µg/L after 168 h
- 218.59 ± 23.03 µg/L after 672 h
The following zinc 5-nitroisophthalate concentrations were calculated on the basis of the molecular formula and a corresponding Zn content of 24.91 %:
- 853.63 ± 20.43 µg/L after 24 h
- 821.64 ± 39.02 µg/L after 168 h
- 877.52 ± 92.45 µg/L after 672 h

Description of key information

Transformation/dissolution test with a loading of 1 mg zinc 5-nitroisophthalate /L media (100 rpm, 21.5 ± 1.5 °C)

Based on measured Zn concentrations, the following zinc 5-nitroisophthalate concentrations were calculated on the basis of the molecular formula and the corresponding Zn content of 24.91 %:

At pH 6:

- 990.65 ± 117.62 µg/L after 24 h

- 752.55 ± 11.56 µg/L after 168 h

- 658.05 ± 21.76 µg/L after 672 h

At pH 8

- 853.63 ± 20.43 µg/L after 24 h

- 821.64 ± 39.02 µg/L after 168 h

- 877.52 ± 92.45 µg/L after 672 h

Key value for chemical safety assessment

Additional information

According to the OECD Series on Testing and Assessment Number 29 (2001), dissolved mean Zn concentrations were measured in a transformation/dissolution test with a loading of 1 mg zinc 5-nitroisophthalate /L media (agitation at 100 rpm, 21.5 ± 1.5 °C) over 672 hours. The following Zn concentrations were determined:

At pH 6:

- 246.77 ± 29.30 µg/L after 24 h

- 187.46 ± 2.88 µg/L after 168 h

- 163.92 ± 5.42 µg/L after 672 h

At pH 8:

- 212.64 ± 5.09 µg/L after 24 h

- 204.67 ± 9.72 µg/L after 168 h

- 218.59 ± 23.03 µg/L after 672 h