Cobalt chromite green spinel

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:

2015-06-12 to 2015-09-28

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

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

Version / remarks:

2001

Deviations:

yes

Remarks:

Determination at pH 6 and 8 instead of 5.5 and 8.5

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2016-05-31

Type of method:

other: transformation / dissolution

Type of test:

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

Mean dissolved conc.:

1.489 µg/L

Element analysed:

Cr

Loading of aqueous phase:

1 other: mg test item/L

Incubation duration:

672 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: SD: ± 0.008 µg/L

Type of test:

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

Mean dissolved conc.:

< 0.783 µg/L

Element analysed:

Cr

Loading of aqueous phase:

1 other: mg test item/L

Incubation duration:

672 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other:

Remarks:

Mean dissolved concentration

Type of test:

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

Mean dissolved conc.:

2.038 µg/L

Element analysed:

Co

Loading of aqueous phase:

1 other: mg test item/L

Incubation duration:

672 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: SD: ± 0.008 µg/L

Type of test:

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

Mean dissolved conc.:

0.79 µg/L

Element analysed:

Co

Loading of aqueous phase:

1 other: mg test item/L

Incubation duration:

672 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: SD: ± 0.039 µg/L

Type of test:

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

Mean dissolved conc.:

9.418 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 other: mg test item/L

Incubation duration:

672 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: SD: ± 0.378 µg/L

Type of test:

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

Mean dissolved conc.:

0.725 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 other: mg test item/L

Incubation duration:

672 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: SD: ± 0.517 µg/L

Type of test:

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

Mean dissolved conc.:

1.84 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 other: mg test item/L

Incubation duration:

672 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: SD: ± 0.378 µg/L, background (means) corrected

Type of test:

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

Mean dissolved conc.:

< 0.096 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 other: mg test item/L

Incubation duration:

672 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other:

Remarks:

Mean dissolved concentration, background (means) corrected

Details on results:

Temperature
The temperature of the thermostatically controlled room was recorded with a Testo 175-T2 data logger. The mean temperature was 20.4 ± 0.2 °C during the test with 1 mg/L loading at pH8. The mean temperature during the test at pH 6 was 20.5 ± 0.2 °C. Therefore, the mean temperature is in agreement with the OECD guidance document 29.

Solution pH and oxygen concentrations
In solutions containing 1 mg/L of the test item at pH 6 and pH 8 as well as in method blanks (BW), the pHs were in the range of 5.9 – 6.3 and 7.7 – 8.2, respectively.

Mass balance
Most of the measured chromium concentrations in samples from the test were below LODs/LOQs (pH 6: 0.5622/1.6867 and 0.4389/1.3167 µg Cr/L; pH 8: 0.7829/2.3486 µg Cr/L) or only slightly above these limits. Therefore, the measured chromium concentrations in samples from the 1 mg/L test were not considered for the mass balance. The Cr concentrations in rinsed filters from pH 6 and pH 8 were mostly below respective LODs/LOQs (pH 6: 0.3775/1.1325 µg/L; pH 8: 01456/0.4368 µg/L). The recovery of Chromium was 0.1 – 0.2 % in all vessels. It is clearly below 100 ± 15 %, indicating that aqua regia is not sufficient for a complete dissolution of the test item. The latter fact is expected for inorganic pigments.

Within-vessel variation and between-vessel variation
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 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 vessel variations may be observed in tests of materials with wider particle size distributions.
For the measured metals these variations are not always within the limits.
Background concentrations for zinc at pH 6 and pH 8 were measured to be in the range of test item loaded samples. Therefore, the measured zinc concentrations from test item loaded vessels at pH 6 and 8 were background (means) corrected.

Method validation summary

Validation parameter	Results	Comment
selectivity	selective wavelength and isotopes for detection and evaluation of Cr, Co and Zn
linearity	applied calibration functions were linear	correlation factor at least 0.999899
limit of detection	Cr: 0.1456 – 0.7829 µg/L Co: 0.1186 – 0.3161 µg/L Zn: 0.0961 – 0.3138µg/L
limit of quantification	Cr: 0.4368 – 2.3486 µg/L Co: 0.3559 – 0.9484 µg/L Zn: 0.2882 – 0.9413 µg/L
accuracy and precision; repeatability	mean recovery for CRM TM-25.4: mass balance pH6 and 8: 101.5 ± 1.7 % (n = 8) Co 238.892 nm: 100.0 ± 1.9 % (n = 19) Zn 213.657 nm: 103.8 ± 3.9 % (n = 16)	Diluted (5 fold) to 4.8 µg Cr/L 5.5 µg Co/L 8.9 µg Zn/L
accuracy and precision	mean recovery for CRM TM-25.4: Cr 206.550 nm: 102.6 ± 2.7 % (n = 8) Cr 284.325 nm: 110.5 ± 6.6 % (n = 8) Co 231.497 nm: 101.9 ± 4.3 % (n = 8) Co 202.548 nm: 98.9 ± 3.4 % (n = 11)	Diluted (5 fold) to 4.8 µg Cr/L 5.5 µg Co/L 8.9 µg Zn/L
accuracy and precision; repeatability	mean recovery for CRM TMDA-53.3: Cr 238.892 nm: 100.3 ± 2.6 % (n = 19) Co 231.497 nm: 101.5 ± 1.4 % (n = 8) Co 234.740 nm: 96.4 ± 2.4 % (n = 6) Zn 213.657 nm: 100.7 ± 3.2 % (n = 16) Zn 202.548 nm: 95.1 ± 2.1 % (n = 18)
accuracy and precision	mean recovery for CRM TMDA-53.3: mass balance pH6 and 8: 100.1 ± 1.3 % (n = 8) Cr 206.550 nm: 100.3 ± 1.6 % (n = 8) Cr 284.325 nm: 103.6 ± 3.4 % (n = 8) Cr 286.674 nm: 99.9 ± 0.9 % (n = 7) Cr 283.563 nm: 99.1 ± 1.0 % (n = 11) Co 231.497 nm: 101.5 ± 1.4 % (n = 8) Co 234.740 nm: 96.4 ± 2.4 % (n = 6)	Diluted (10 fold) to 34.1 µg Cr/L 25.1 µg Co/L 38.6 µg Zn/L
accuracy and precision; repeatability	mean recovery for quality control standard: Co 238.892 nm: 96.4 ± 1.9 % (n = 16) Zn 213.657 nm: 98.3 ± 2.8 % (n = 16)	Mixture of multi standards XVII : XXI (1:1) diluted to 10 µg/L
accuracy and precision	Mean recovery for quality control standard: mass balance pH6 and 8: 100.6 ± 1.4 % (n = 8) Cr 206.550 nm: 99.0 ± 2.1 % (n = 8) Cr 284.325 nm: 101.7 ± 2.4 % (n = 8) Cr 283.563 nm: 92.4 ± 1.3 % (n = 8) Co 231.497 nm: 100.6 ± 2.4 % (n = 8) Zn 213.657 nm: 98.3 ± 2.8 % (n = 16) Zn 202.548 nm: 95.4 ± 1.6 % (n = 8)	Mixture of multi standards XVII : XXI (1:1) diluted to 10 µg/L
accuracy and precision; repeatability	Mean recovery for quality control standard: Zn 202.548 nm: 98.4 ± 1.1 % (n = 10)	Mixture of multi standards XVII : XXI (1:1) diluted to 100 µg/L
accuracy and precision	Mean recovery for quality control standard: Cr 283.563 nm: 96.1 ± 0.2 % (n = 3) Cr 286.674 nm: 96.2 ± 0.7 % (n = 7) Co 238.892 nm: 96.1 ± 1.0 % (n = 3) Co 234.740 nm: 96.6 ± 1.1 % (n = 7)	Mixture of multi standards XVII : XXI (1:1) diluted to 100 µg/L
accuracy and precision; repeatability	Mean recovery for recalibration standard: mass balance pH6 and 8: 99.5 ± 1.7 % (n = 8) Co 238.892 nm: 95.6 ± 2.6 % (n = 16) Zn 213.657 nm: 101.1 ± 2.4 % (n = 16)	Diluted to 5 µg Cr, Co, Zn/L
accuracy and precision	Mean recovery for quality control standard: Cr 206.550 nm: 99.0 ± 2.1 % (n = 8) Cr 284.325 nm: 106.2 ± 4.9 % (n = 8) Co 231.497 nm: 98.9 ± 5.5 % (n = 8) Zn 213.657 nm: 98.3 ± 2.8 % (n = 16) Zn 202.548 nm: 85.7 ± 1.0 % (n = 8)	Diluted to 5 µg Cr, Co, Zn/L
accuracy and precision; repeatability	Zn 202.548 nm: 93.4 ± 0.8 % (n = 10)	Diluted to 50 µg Cr, Co, Zn/L
accuracy and precision	Mean recovery for quality control standard: Cr 286.647 nm: 95.6 ± 0.9 % (n = 7) Cr 283.563 nm: 97.8 ± 2.0 % (n = 3) Co 238.892 nm: 96.6 ± 0.2 % (n = 3) Co 234.740 nm: 95.8 ± 1.6 % (n = 7)	Diluted to 50 µg Cr, Co/L
trueness	recovery of fortified samples: Cr: 85.2 – 107.2 % (n = 10) Co: 85.3 – 102-1 % (n = 15) Zn: 86.1 – 115.3 % (n = 11)

Recoveries of fortified samples (values were rounded, internal calculations were performed with more digits)

sample	Measured concentration [µg M/L]	calculated level after addition [µg M/L]	recovery [µg M/L] / [%]
1 mL of sample + 4 mL of 25 µg Cr/L
Mass balance sample a from vessel 1	4.93	20.99	20.24 / 96.5
Sample a from vessel 1 after 6h	<LOD	20	17-05 / 85.2
1 mL of sample + 4 mL of 10 µg Cr/L
Sample a from vessel 4 after 2h	0.014	8.003	8.123 / 101.5
Sample a from vessel 4 after 6h	0.242	8.048	8.105 / 100.7
Sample a from vessel 4 after 24h	0.612	8.122	8.079 / 99.5
Sample a from vessel 4 after 96h	1.06	8.212	7.803 / 95.0
Sample a from vessel 4 after 168h	0.660	8.132	8.873 / 109.1
Sample a from vessel 4 after 336h	1.019	8.204	8.660 / 105.6
Sample a from vessel 4 after 504h	1.138	8.228	8.823 / 107.2
Sample a from vessel 4 after 672h	1.079	8.216	8.667 / 105.5
1 mL of sample + 4 mL of 25 µg Co/L
Sample a from vessel 1 after 2h	<LOD	20.00	17.57 / 87.8
Sample a from vessel 1 after 6h	<LOD	20.00	18.23 / 91.1
Sample a from vessel 1 after 24h	<LOD	20.00	17.97 / 89.9
Sample a from vessel 1 after 168h	<LOD	20.00	18.24 / 91.2
Sample a from vessel 1 after 336h	0.968	20.19.	17.22 / 85.3
Sample a from vessel 1 after 504h	<LOD	20.00	17.94 / 89.7
Sample a from vessel 1 after 672h	<LOD	20.00	18.31 / 91.5
1 mL of sample + 4 mL of 10 µg Co/L
Sample a from vessel 4 after 2h	0.973	8.195	8.254 / 100.7
Sample a from vessel 4 after 6h	0.934	8.187	7.970 / 97.4
Sample a from vessel 4 after 24h	1.482	8.296	7.856 / 94.7
Sample a from vessel 4 after 96h	1.561	8.312	8.489 / 102.1
Sample a from vessel 4 after 168h	1.802	8.360	8.065 / 96.5
Sample a from vessel 4 after 336h	1.891	8.378	8.111 / 96.8
Sample a from vessel 4 after 504h	1.909	8.382	8.111 / 96.8
Sample a from vessel 4 after 672h	1.856	8.371	8.105 / 96.8
1 mL of sample + 4 mL of 25 µg Zn/L
Sample a from vessel 1 after 2h	<LOD	20.00	17.22 / 86.1
Sample a from vessel 1 after 6h	<LOD	20.00	17.49 / 87.4
Sample a from vessel 1 after 96h	1.019	20.20	17.43 / 86.3
Sample a from vessel 1 after 168h	<LOD	20.00	17.54 / 87.7
Sample a from vessel 1 after 336h	0.721	20.14	17.44 / 86.6
Sample a from vessel 1 after 504h	<LOD	20.00	18.00 / 90.0
1 mL of sample + 4 mL of 10 µg Zn/L
Sample a from vessel 4 after 96h	4.428	8.886	10.242 / 115.3
Sample a from vessel 4 after 168h	7.239	9.448	9.842 / 104.2
Sample a from vessel 4 after 336h	6.540	9.308	9.340 / 100.3
Sample a from vessel 4 after 504h	8.148	9.630	9.772 / 101.5
Sample a from vessel 4 after 672h	8.727	9.745	9.998 / 102.6

Conclusions:

According to the OECD Series on Testing and Assessment Number 29 (2001), dissolved mean Cr, Co, Zn concentrations were determined in a transformation/dissolution test with a loading of 1 mg test item (cobalt chromite green spinel) /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 concentrations were determined after 672 h:
pH 6 pH 8
Cr [µg/L] 1.489 ± 0.008 Co [µg/L] 2.038 ± 0.008 0.790 ± 0.039
Zn [µg/L] 9.418 ± 0.378 0.725 ± 0517
Zn [µg/L] background (means) corrected 1.840 ± 0.378

Description of key information

Transformation/dissolution test of cobalt chromite green spinel with a loading of 1 mg/L media at 21.5 ± 1.5 °C after 672 h:

- Cr [µg/L]: 1.489 ± 0.008 (pH 6); <LOD (<0.7829) (pH 8)

- Co [µg/L]: 2.038 ± 0.008 (pH 6); 0.790 ± 0.039 (pH 8)

- Zn [µg/L] background (means) corrected: 1.840 ± 0.378 (pH 6); <LOD (<0.0961) (pH 8)

Additional information

According to the OECD Series on Testing and Assessment Number 29 (2001), dissolved mean Cr, Co, Zn concentrations were determined in a transformation/dissolution test with a loading of 1 mg test item (cobalt chromite green spinel) /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 concentrations were determined after 672 h:

  

	pH 6	pH 8
Cr [µg/L]	1.489 ± 0.008	<LOD (<0.7829)
Co [µg/L]	2.038 ± 0.008	0.790 ± 0.039
Zn [µg/L]	9.418 ± 0.378	0.725 ± 0517
Zn [µg/L] background (means) corrected	1.840 ± 0.378	<LOD (<0.0961)