Zirconium zircon with encapsulated cadmium selenium sulphide

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2011-12-07 to 2012-09-18

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

deviations do not effect the validity of the study

Qualifier:

according to guideline

Guideline:

other: OECD Series 29 (2001)

Deviations:

yes

Remarks:

the full 28-day test with a loading of 1 mg/Lwas conducted at a pH of 6 and 8 instead of 5.5 and 8.5. / The within- and between-vessel variation was sometimes higher than demanded.

GLP compliance:

yes (incl. QA statement)

Remarks:

signed on 2011-02-07

Type of method:

flask method

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.07 µg/L

Element analysed:

Cd

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 8, 21.2 °C

Remarks on result:

other: S.D.: ± 0.02 µg/L

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.18 µg/L

Element analysed:

Cd

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 8, 22 °C

Remarks on result:

other: S.D.: ± 0.05 µg/L

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.34 µg/L

Element analysed:

Cd

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 8, 22.3 °C

Remarks on result:

other: S.D.: ± 0.09 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.18 µg/L

Element analysed:

Cd

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 6, 21.4 °C

Remarks on result:

other: S.D.: ± 0.05 µg/L

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.41 µg/L

Element analysed:

Cd

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6, 21.2 °C

Remarks on result:

other: S.D.: ± 0.19 µg/L

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.86 µg/L

Element analysed:

Cd

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6, 21.5 °C

Remarks on result:

other: S.D.: ± 0.39 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

1.97 µg/L

Element analysed:

Cd

Loading of aqueous phase:

10 mg/L

Incubation duration:

7 d

Test conditions:

pH 6, 21.9 °C

Remarks on result:

other: S.D.: ± 0.34 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

3.13 µg/L

Element analysed:

Cd

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

pH 6, 22.2 °C

Remarks on result:

other: S.D.: ± 0.40 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.09 µg/L

Element analysed:

Se

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 8, 21.2 °C

Remarks on result:

other:

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.05 µg/L

Element analysed:

Se

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 8, 22 °C

Remarks on result:

other: S.D.: ± 0.01 µg/L

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.14 µg/L

Element analysed:

Se

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 8, 22.3 °C

Remarks on result:

other: ≤LOQ (0.14 µg/L)

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.03 µg/L

Element analysed:

Se

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 6, 21.4 °C

Remarks on result:

other:

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.05 µg/L

Element analysed:

Se

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6, 21.2 °C

Remarks on result:

other: S.D.: ± 0.01 µg/L

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.14 µg/L

Element analysed:

Se

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6, 21.5 °C

Remarks on result:

other:

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.16 µg/L

Element analysed:

Se

Loading of aqueous phase:

10 mg/L

Incubation duration:

7 d

Test conditions:

pH 6, 21.9 °C

Remarks on result:

other: S.D.: ± 0.03 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.44 µg/L

Element analysed:

Se

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

pH 6, 22.2 °C

Remarks on result:

other: S.D.: ± 0.12 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.002 µg/L

Element analysed:

Zr

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 8, 21.2 °C

Remarks on result:

other:

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.003 µg/L

Element analysed:

Zr

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6 (21.2 °C) and pH 8 (22.0 °C)

Remarks on result:

other:

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.002 µg/L

Element analysed:

Zr

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 8, 22.2 °C

Remarks on result:

other:

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.002 µg/L

Element analysed:

Zr

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 6, 21.4 °C

Remarks on result:

other:

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.001 µg/L

Element analysed:

Zr

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6, 21.5 °C

Remarks on result:

other:

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.12 µg/L

Element analysed:

Zr

Loading of aqueous phase:

10 mg/L

Incubation duration:

7 d

Test conditions:

pH 6, 21.9 °C

Remarks on result:

other: < LOQ (0.12)

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.04 µg/L

Element analysed:

Zr

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

pH 6, 22.2 °C

Remarks on result:

other:

Details on results:

Temperature
The temperature of the thermostatically controlled room was recorded with a data logger. The mean temperatures were 21.6 ± 0.4 °C for 1 mg/L test and 21.1 ± 0.7 °C for the 10 and 100 mg/L test. Therefore the mean temperature is in agreement with the OECD guidance document 29.

pH
According to the guidance, the solution pH can be expected to remain constant (± 0.2 units) during most tests.
The solution pH remained relatively constant during the 28 days for both pH treatments in vessels containing 1 mg/L of the test item and in method blanks, pH was in the range of 7.8 – 8.0 and 5.9 – 6.4, respectively.
The solution pH remained relatively constant during the 7 days for the pH6 treatment in vessels containing 10 and 100 mg/L of the test item and in method blanks, pH was in the range of 5.8 – 6.3.

Oxygen
Oxygen levels in all test vessels and 1 mg /L 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).
Oxygen levels in all test vessels and 10 and 100 mg/L 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)

Mass balance
After 12h of digestion with added aqua regia, insoluble residues were observed in all vessels, indicating an incomplete dissolution/transformation of the test item. Therefore, the pigment could not be dissolved and the recovery is < 100 % for the element cadmium in media at pH 6.

Method validation summary (ICP-OES)

validation parameter	results	comment
Selectivity	similar data with different element wavelengths for ICP-OES method	no interferences observed
Linearity	applied calibration functions were linear	correlation coefficient at least 0.9999
Limit of detection	Cd: 3.30 µg/L, Se: 4.66 µg/L, Zr: 3.51 µg/L
Limit of quantification	Cd: 11.0 µg/L, Se: 15.5 µg/L, Zr: 11.7 µg/L
Accuracy	mean recovery for CRM TMDA-70 (mass balance): Cd: 103 ± 1.1 (n = 4), Se: 107 ± 5.2 (n = 4)	higher concentration range for Cd (145 µg/L) and lower concentration range for Se (13.0 µg/L)
Trueness (Cd and Se)	mean recovery for recalibration standard (mass balance): Cd: 97.5 ± 1.2 % (n = 4), Se: 96.5 ± 1.9 % (n = 4)	high concentration range (100 µg/L Cd and Se, respectively)
Trueness (Zr)	mean recovery for recalibration standard (mass balance): Zr: 98.7 ± 1.9 % (n = 4)	high concentration range (50 µg/L)
Reproducibility	mean recovery for CRM TMDA-70 (mass balance): Cd: 103 ± 1.1 (n = 4), Se: 107 ± 5.2 (n = 4)	higher concentration range for Cd (145 µg/L) and lower concentration range for Se (13.0 µg/L)

Method validation summary (ICP-MS)

validation parameter	results	comment
Selectivity	similar data with at least two different isotopes for ICP-MS method	no interferences observed, measurements with best recoveries of reference material were used for calculation
Linearity	applied calibration functions were linear	correlation factor at least 0.9982
Limit of detection	Cd: 0.002 – 0.03 µg/L, Se: 0.01 – 0.15 µg/L, Zr: 0.0004 – 0.05 µg/L
Limit of quantification	Cd: 0.01 – 0.09 µg/L Se: 0.02 – 0.44 µg/L, Zr: 0.001 – 0.14 µg/L
Method blanks Cd 1mg loading (total: 96 samples)	54 samples <LOD (0.002 – 0.01 µg/L), 32 samples <LOQ (<0.01 – 0.03 µg/L), 10 samples >LOQ	method blanks >LOQ are below the sample concentration (> factor 90)
Method blanks Cd 10 and 100 mg loading (total: 30 samples)	Concentrations of cadmium in all method blanks above the LOQ (0.02 – 0.09 µg/L)	used chemicals and vessels checked for possible potential contaminations ==> source of contamination was not detected
Method blanks Se all loadings	Mainly all method blanks below LOD (0.01 – 0.15 µg/L) or LOQ (<0.02 - 0.44 µg/L); one method blank sample (vessel 2 sample a 168h pH8) above LOQ of measurement series (concentration 0.02 µg/L; LOQ 0.02 µg/L)	method blank >LOQ are at least 60.7 % below the sample concentration
Method blanks Zr all loadings	Mainly all method blanks below LOD (0.0004 – 0.01 µg/L); one method blank sample (vessel 1 sample a 2h pH6) above LOQ of measurement series (concentration 0.11 µg/L)	method blank >LOQ are at least 46.3 % below the sample concentration; method blanks after 2h were always below LOD
Accuracy Cd	mean recovery for CRM TMDA-70 (145 µg Cd/L): 104 ± 4.7 % (n = 20) ) mean recovery for CRM TM-DWS.2 (4.2 µg Cd/L): 104 ± 5.2 % (n = 38)	high concentration range of samples low concentration range of samples
Acuracy Se	mean recovery for CRM TMDA-70 (25.8 µg Se/L): 99.5 ± 8.2 % (n = 32) mean recovery for CRM TM-DWS.2 (8.65 µg Se/L): 104 ± 3.9 % (n = 20)	high concentration range of samples low concentration range of samples
Accuracy Zr	mean recovery for standard solution (1 µg Zr/L): 99.2 ± 6.3 % (n = 30) mean recovery for standard solution (0.5 µg Zr/L): 95.5 ± 5.7 % (n = 20)	high concentration range of samples low concentration range of samples
Trueness Cd	mean recovery for CPI standard (10 µg/L): 98.7 ± 3.8 % (n = 12) mean recovery for recalibration standard (5 µg/L): 100 ± 4.1 % (n = 11)	high concentration range low concentration range
Trueness Se	mean recovery for CPI standard (10 µg/L): 100 ± 3.7 % (n = 12) mean recovery for recalibration standard (5 µg/L): 102 ± 4.4 % (n = 11)	high concentration range low concentration range
Trueness Zr	mean recovery for standard solution (1 µg Zr/L): 99.2 ± 6.3 % (n = 30) mean recovery for standard solution (0.5 µg Zr/L): 95.5 ± 5.7 % (n = 20)	high concentration range low concentration range
Reproducibility Cd	mean recovery for CRM TMDA-70 (145 µg Cd/L): 104 ± 4.7 % (n = 20) mean recovery for CRM TM-DWS.2 (4.2 µg Cd/L): 104 ± 5.2 % (n = 32)	high concentration range low concentration range
Reproducibility Se	mean recovery for CRM TMDA-70 (25.8 µg Se/L): 102 ± 4.6 % (n = 20) mean recovery for CRM TM-DWS.2 (8.65 µg Se/L): 99.5 ± 8.2 % (n = 32)	high concentration range low concentration range
Reproducibility Zr	mean recovery for standard solution (1 µg Zr/L): 99.2 ± 6.3 % (n = 30) mean recovery for standard solution (0.5 µg Zr/L): 95.5 ± 5.7 % (n = 20)	high concentration range low concentration range

Loading 1 mg/L pH 8:

Cadmium: The observed variations within the test flasks were in compliance with the guidance except for the within-vessel variations of vessel 2 (11.8 %) after 504 h and vessel 3 (12.8 %) after 672 h. The observed variations between the test flasks over the experimental period were in the range of 17.6 – 26.7 %.

Selenium: Because nearly all measured selenium concentrations were below the LOD or LOQ respectively, a variation within test flask could only be calculated for the concentrations after 168 and 336 h. The observed within-vessel variations are 19.3 % for vessel 1 and 27.1 % for vessel 3 after 168 h as well as 20.6 % for vessel 1 and 27.5 % for vessel 2 after 336 h. The within-vessel variation of vessel 2 after 168 h and vessel 3 after 336 h is in compliance with the OECD guideline. The observed variations between the test flasks over the experimental period were in the range of 28.2 – 28.8 % (sampling point 168 h and 336 h only).

Zirconium: The concentrations of zirconium were always below the LOD or LOQ except for vessel 1 after 504 h (0.003 μg/L). Therefore no within- or and between vessels variations could be calculated.

Loading 1 mg/L pH 6:

Cadmium: The observed variations within the test flasks were in compliance with the guidance document except for the within-vessel variations of vessel 4 and 5 (22.5 and 12.5 %) after 2 h, vessel 5 (12.5 %) after 6 h and vessel 5 (14.2 %) after 504 h. The observed variations between the test flasks over the experimental period were in the range of 22.3 – 53.6 %.

Selenium: Nearly all measured selenium concentrations were below LOD or LOQ respectively, and the variation within test flasks could only be calculated for the concentrations after 168 and 336 h. The observed variations within the test flasks were in compliance with the guidance document except for the within-vessel variations for vessel 2 (32.9 %) after 168 h and for vessel 4 and 5 (18.5 % and 26.0 %) after 336 h. The observed variations between the test flasks over the experimental period were in the range of 27.5 – 39.9 % (sampling point 168 h and 336 h only).

Zirconium: The concentrations of zirconium were always below the LOD or LOQ. Therefore no within- or between vessels variations could be calculated.

Loading 10 mg/L pH 6:

Cadmium: The observed variations within the test flasks were in compliance with the guidance document except for the within-vessel variations of vessel 2 (10.3 %) after 24 h. The observed variations between the test flasks over the experimental period were in the range of

8.2 – 32.1 %.

Selenium: The observed variations within the test flasks were not in compliance with the guidance document for vessel 1, 2 and 3 (12.5 - 25.0 %) after 2 h, vessel 1 (34.8 %) after 6 h, vessel 1 and 2 (10.6 – 28.8 %) after 24 h, vessel 2 (15.6 %) after 96 h and vessel 2 and 3 (10.3 – 23.8 %) after 168 h. The observed variations between the test flasks over the experimental period were in the range of 10.4 – 37.5 %.

Zirconium: The concentrations of zirconium were below the LOD or LOQ except for vessel 1 after 96 h and 168 h. In vessel 1 after 96 h a concentration of 0.20 ± 0.01 μg/L and for vessel 1 after 168 h a concentration of 0.165 μg/L (only sample) were detectable. For this reason only for vessel 1 after 96 h a within-vessel variation could be calculated (3.1 %) which is in compliance with the guideline. Between vessels variations could not be calculated.

Loading 100 mg/L pH 6:

Cadmium: The observed variations within the test flasks were in compliance with the guidance document except for the within-vessel variations of vessel 5 (12.5 %) after 6 h and vessel 4 (10.8 %) after 24 h. The observed variations between the test flasks over the experimental period were in the range of 8.3 – 18.2 %.

Selenium: The observed variations within the test flasks were mainly in compliance with the guidance document except for the within-vessel variations of vessel 5 and 6 (10.3 - 17.1 %) after 2 h, vessel 4 and 6 (11.1 – 15.0 %) after 6 h and vessel 5 (14.2 %) after 168 h. The observed variations between the test flasks over the experimental period were in the range of 9.0 – 51.2 %.

Zirconium: The concentrations of zirconium were always below the LOD or LOQ. Therefore no within- or between vessels variations could be calculated.

Loading 10 mg/L pH6 with subtraction of mean cadmium concentration in method blanks:

Cadmium: The observed variations within the test flasks were in compliance with the guidance document except for the within-vessel variations of vessel 1 and 3 (21.0 and 17.1 %) after 6 h and vessel 2 and 3 (17.1 and 10.6 %) after 24 h. The observed variations between the test flasks over the experimental period were in the range of 32.5 – 38.0 %.

Loading 100 mg/L pH6 with subtraction of mean cadmium concentration in method blanks:

Cadmium: The observed variations within the test flasks were in compliance with the guidance document except for the within-vessel variations of vessel 5 (15.7 %) after 6 h and vessel 4 (12.3 %) after 24 h. The observed variations between the test flasks over the experimental period were in the range of 10.3 – 24.3 %.

According to the guidance, 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 %. The observed increased between-vessel variations might may be due to be the wider particle size distribution of the test item (D10, D50, D90 = 4.4, 11.4, 23.3 μm, respectively). 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.

Conclusions:

Transformation/dissolution of silicic acid, zirconium salt, cadmium pigment encapsulated was investigated according to the method OECD test series No. 29
(Guidance document on transformation/dissolution of metals and metal compounds in aqueous media). Under the described conditions of this test with IPC-2013-001 (Silicic acid, zirconium salt, cadmium pigment-encapsulated), the following dissolved concentrations were measured at the respective loading, exposure and solution pH:
1 mg/L loading after 7 days:
-      Cadmium: 0.18 µg/L and 0.41 µg/L at pH 8 and pH 6, respectively
-      Selenium: 0.05 µg/L at pH 8 and pH 6, respectively
-      Zirconium: 
1 mg/L loading after 28 days:
-      Cadmium: 0.34 µg/L and 0.86 µg/L at pH 8 and pH 6, respectively
-      Selenium: -      Zirconium: 
The dissolved Cd, Se and Zr concentrations were below 1 µg/L, referring to a solubility of < 0.1 %. Thus, the extent to which " silicic acid, zirconium salt, cadmium pigment encapsulated " can produce soluble available ionic and other metal-bearing species in aqueous media is limited.

Description of key information

A GLP-conform transformation/dissolution test with a loading of 1 mg/L at pH 6 and ph 8 over 28 days, revealed higher dissolution at ph 6 than at pH 8. Dissolved Zr concentration at pH 6 were below the LOD/ LOQ after 7 and 28 days. Dissolved Se concentration were measured to be 0.05 microg/L after 7 and below the LOD/LOQ after 28 days (Knopf, 2013). Dissolved Cd concentration were measured to be 0.41 microg/L after 7 and 0.86 microg/L after 28 days (Knopf, 2013). Transformation/dissolution at a loading of 10 mg/L resulted in dissolved Cd, Se and Zr concentrations at pH 6 after 7 of 1.97 mircog/L, 0.16 microg/L and < LOQ, respectively (Knopf, 2013). Transformation/dissolution at a loading of 100 mg/L resulted in dissolved Cd, Se and Zr concentrations at pH 6 after 7 of 3.13 mircog/L, 0.44 microg/L and < LOD, respectively (Knopf, 2013). The particle size of the tested sample (BET surface area 0.38 m2/g) is representative for the particle size marketed.

 

Therefore, the solubility of Zirconium zircon with encapsulated cadmium selenium sulphide is < 0.1% after 28 days at 1 mg/L loading. Thus, the extent to which " Zirconium zircon with encapsulated cadmium selenium sulphide" can produce soluble available ionic and other metal-bearing species in aqueous media is limited.