Spinels, cobalt tin grey

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:

2015-04-28 to 2015-07-15

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.:

0.353 µg/L

Element analysed:

Sn

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: ± 0.0853 µg/L

Type of test:

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

Mean dissolved conc.:

2.921 µg/L

Element analysed:

Sn

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: ± 0.6034 µg/L

Type of test:

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

Mean dissolved conc.:

0.486 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: ± 0.0473 µg/L

Type of test:

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

Mean dissolved conc.:

0.78 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: ± 0.2988 µg/L

Type of test:

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

Mean dissolved conc.:

0.764 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: ± 0.2988 µg/L

Remarks:

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 20.3 ± 0.2 °C during the test with 1 mg/L loading at pH 6 and pH 8. 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, the pHs were in the range of 5.9 – 6.7 and 7.5 – 8.1, respectively. In method blanks (BW) at pH 6 and pH 8, the pHs were in the range of 5.8 – 6.4 and 7.5 – 8.1, respectively.

Mass balance
Cobalt is chosen as representative element for mass balance. The recovery was 83.4 % - 109.2 % for pH 6. Total cobalt in vessel 3 could not be calculated because the measured concentration in vessel 3 was below LOQ (<1.1310 µg Co/L). The recovery at pH 8 was 73.7 % - 88.0 %. These results show that cobalt cannot be easily dissolved out of the test item (with aqua regia) as 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 cobalt and tin concentrations these variations are mostly within these limits.
Background concentrations for cobalt at pH 6 and 8 were measured to be in the range of test item loaded samples. Therefore, the measured concentrations from test item loaded vessels at both pHs were background (means) corrected.

Method validation summary

Validation parameter	Results	Comment
selectivity	selective wavelength and isotopes for detection and evaluation of Co and Zn
linearity	applied calibration functions were linear	correlation factor at least 0.9996
limit of detection	Co: 0.0001 – 0.40042 µg/L Sn: 0.0019 – 0.0048 µg/L
limit of quantification	Co: 0.0004 – 0.0126 µg/L Sn: 0.0058 – 0.0145 µg/L
accuracy and precision; repeatability	Mean recovery for certified reference material TM-25.4: ^59Co*: 101.8 ± 2.1 % (n = 41) ^120Sn**: 104.9 ± 4.3 % (n = 34)	Diluted to 5.5 µg Co/L 4.76 µg Sn/L
accuracy and precision	Mean recovery for certified reference material TM-25.4: Mass balance Co 231.160 nm: 102.3 ± 3.0 % (n = 2)	Diluted to 5.5 µg Co/L
accuracy and precision	Mean recovery for certified reference material TM-25.4: ^59Co*: 101.1 ± 2.0 % (n = 11) ^120Sn** : 101.4 ± 0.9 % (n = 11)	Diluted to 2.75 µg Co/L 2.38 µg Sn/L
accuracy and precision	Mean recovery for certified reference material TM-25.4: ^59Co*: 98.6 ± 1.1 % (n = 7) ^120Sn**: 97.8 ± 3.7 % (n = 7)	Diluted to 1.375 µg Co/L 1.19 µg Sn/L
accuracy and precision	Mean recovery for certified reference material TM-25.4: ^118Sn**: 107.0 ± 1.6 % (n = 7)	Diluted to 4.76 µg Sn/L
accuracy and precision; repeatability	Mean recovery for certified reference material TMDA-53.3: ^59Co*: 100.9 ± 2.2 % (n = 41) ^120Sn**: 102.8 ± 4.7 % (n = 41)	Diluted to 25.1 µg Co/L 1.84 µg Sn/L
accuracy and precision	Mean recovery for certified reference material TMDA-53.3: Mass balance Co 231.160 nm: 101.8 ± 3.1 % (n = 2)	Diluted to 25.1 µg Co/L
accuracy and precision	Mean recovery for certified reference material TMDA-53.3: ^59Co*: 101.6 ± 1.6 % (n = 11) ^120Sn**: 102.8 ± 3.3 % (n = 11)	Diluted to 50.2 µg Co/L 3.68 µg Sn/L
accuracy and precision	Mean recovery for certified reference material TMDA-53.3: ^118Sn**: 106.6 ± 1.6 % (n = 7)	Diluted to 1.84 µg Sn/L
accuracy and precision; repeatability	Mean recovery for quality control standard QC: ^59Co**: 98.7 ± 2.1 % (n = 16) ^120Sn**: 103.2 ± 1.5 % (n = 9)	Diluted to 10 µg Co and Sn/L
accuracy and precision	Mean recovery for quality control standard QC: Mass balance Co 231.160 nm: 99.2 ± 1.6 % (n = 2)	Diluted to 10 µg Co/L
accuracy and precision	Mean recovery for quality control standard QC: ^59Co*: 101.6 ± 1.6 % (n = 11) ^120Sn**: 102.8 ± 3.3 % (n = 11)	Diluted to 50.2 µg Co/L 3.68 µg Sn/L
accuracy and precision	Mean recovery for quality control standard QC: ^118Sn**: 107.0 ± 1.6 % (n = 7)	Diluted to 10 µg Sn/L
accuracy and precision; repeatability	Mean recovery for quality control standard QC: ^59Co*: 96.1 ± 2.1 % (n = 43) ^120Sn**: 97.0 ± 2.5 % (n = 43)	Diluted to 5 µg Co and Sn/L
accuracy and precision; repeatability	Mean recovery for recalibration standard: ^59Co*: 98.2 ± 3.0 % (n = 43) ^120Sn**: 99.0 ± 3.0 % (n = 43)	Diluted to 10 µg Co and Sn/L
accuracy and precision	Mean recovery recalibration standard: ^59Co*: 99.0 ± 1.3 % (n = 7) ^118Sn**: 102.4 ± 2.5 % (n = 7) Mass balance Co 231.160 nm: 103.2 ± 2.8 % (n = 2)	Diluted to 5 µg Co and Sn/L
accuracy and precision	Mean recovery recalibration standard: ^59Co*: 98.4 ± 1.5 % (n = 9) ^120Sn**: 102.2 ± 2.1 % (n = 9)	Diluted to 0.5 µg Co and Sn/L
trueness	Co: 96.1 – 106.9 (n = 16) Sn: 97.6 - 106.5 (n = 15)

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

Sample	Measured conc. [µg Co/L]	Calculated level after addition [µg Co/L]	Recovery [µg Co/L]	Recovery [%]	Measured conc [µg Sn/L]	Calculated level after addition [µg Sn/L]	Recovery [µg Sn/L]	Recovery [%]
1 mL of sample + 2 mL of 0.5 µg M/L
Sample a from vessel 1 after 2h	0.0196	3.340	3.457	103.5	0.060	3.353	3.547	105.8
Sample a from vessel 4 after 2h	0.0515	3.350	3.513	104.8	0.098	3.366	3.436	102.1
Sample a from vessel 1 after 6h	0.0336	3.345	3.260	97.5	0.091	3.364	3.285	97.7
Sample a from vessel 4 after 6h	0.0804	3.360	3.230	96.1	0.161	3.387	3.305	97.6
Sample a from vessel 1 after 24h	0.0679	3.356	3.426	102.1	0.122	3.374	3.397	100.7
Sample a from vessel 4 after 24h	0.1694	3.390	3.291	97.1	0.337	3.446	3.554	103.2
Sample a from vessel 4 after 96h	0.2589	3.420	3.437	100.5	0.452	3.484	3.494	100.3
Sample a from vessel 4 after 168h	0.3624	3.454	3.523	102.0	0.692	3.564	3.490	97.9
Sample a from vessel 4 after 336h	0.4261	3.475	3.434	98.8	0.651	3.550	3.635	102.4
Sample a from vessel 4 after 504h	0.4457	3.482	3.426	98.4	0.544	3.515	3.558	101.2
Sample a from vessel 4 after 672h	0.4374	3.479	3.439	98.8	0.452	3.484	3.598	103.3
Sample a from vessel 1 after 168	0.3607	3.454	3.513	101.7	1.321	3.774	4.019	106.5
Sample a from vessel 1 after 96h	0.3607	3.454	3.513	101.7	1.321	3.774	4.019	106.5
Sample a from vessel 4 after 336h	0.7122	0.571	0.559	98.0	3.083	1.361	1.394	102.4
Sample a from vessel 4 after 504h	0.7339	0.578	0.610	105.6	3.156	1.385	1.410	101.8
0.5 mL of sample + 4.5 mL of 2.5 µg Co/L
Mass balance sample from filter 1	1.586	2.251	2.406	106.9

                                                   

                                                   

Conclusions:

According to the OECD Series on Testing and Assessment Number 29 (2001), dissolved mean Co, Sn concentrations were determined in a transformation/dissolution test with a loading of 1 mg test item (cobalt magnesium tin 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
Sn [µg/L] 0.3531 ± 0.0853 2.9213 ± 0.6034
Co [µg/L] 0.4861 ± 0.0473 0.7801 ± 0.2988
Co [µg/L] background (means) corrected - 0.7638 ± 0.2988

Description of key information

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

- Sn: 0.3531 ± 0.0853 µg/L (pH 6); 2.9213 ± 0.6034 µg/L (pH 8)

- Co: 0.4861 ± 0.0473 µg/L (pH 6); 0.7801 ± 0.2988 µg/L (pH 8)

- Co (background (means) corrected): 0.7638 ± 0.2988 µg/L (pH 8)

Additional information

According to the OECD Series on Testing and Assessment Number 29 (2001), dissolved mean Co, Sn concentrations were determined in a transformation/dissolution test with a loading of 1 mg test item (cobalt magnesium tin 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
Sn [µg/L]	0.3531 ± 0.0853	2.9213 ± 0.6034
Co [µg/L]	0.4861 ± 0.0473	0.7801 ± 0.2988
Co [µg/L] background (means) corrected	-	0.7638 ± 0.2988