Cobalt zinc silicate blue phenacite

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:

2015-05-06 to 2015-06-15

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.:

123.59 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: ± 9.79 µg/L

Type of test:

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

Mean dissolved conc.:

12.43 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: ± 4.02 µg/L

Type of test:

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

Mean dissolved conc.:

201.56 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: ± 16.88 µg/L

Type of test:

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

Mean dissolved conc.:

18.31 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: ± 7.63 µg/L

Type of test:

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

Mean dissolved conc.:

193.98 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: ± 16.88 µg/L

Remarks:

background (means) corrected

Type of test:

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

Mean dissolved conc.:

16.54 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: ± 5.43 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 ± 0.3 °C during the test with 1 mg/L loading at pH 6 and 21.0 ± 0.6 °C during the test at 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 – 6.6 and 7.6 – 8.1, respectively. In method blanks (BW) at pH 6 and pH 8, the pHs were in the range of 5.9 – 6.3 and 7.8 – 8.2, respectively.

Mass balance
Cobalt is chosen as representative element for mass balance. The recovery was 100.9 % - 111.9 % for pH 6 and 91.9 – 94.9 % for pH 8.

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 zinc concentrations these variations are mostly within these limits
Background concentrations for zinc and at pH 8 and pH 6 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 0.999899
limit of detection	Co: 0.1186 – 0.4878 µg/L Zn: 0.0149 – 0.3138 µg/L
limit of quantification	Co: 0.3559 – 1.4635 µg/L Zn: 0.0448 – 0.9413 µg/L
accuracy and precision; repeatability	Mean recovery for quality control standard QC: Co 228.615 nm: 97.5 ± 1.7 % (n = 12) Zn 213.857 nm: 98.3 ± 2.8 % (n = 16) Co 238.892 nm: 97.1 ± 2.3 % (n = 20)	Diluted to 10 µg Co, Zn/L
accuracy and precision	Mean recovery for quality control standard QC: Zn 202.548 nm: 95.4 ± 1.6 % (n = 8)	Diluted to 10 µg Zn/L
accuracy and precision; repeatability	Mean recovery for recalibration standard: Co 228.615 nm: 94.5 ± 1.8 % (n = 12) Zn 213.857 nm: 101.0 ± 2.4 % (n = 16) Co 238.892 nm: 96.2 ± 3.0 % (n = 20)	Diluted to 5 µg Co, Zn/L
accuracy and precision	Mean recovery for recalibration standard: Zn 202.548 nm: 85.7 ± 1.0 % (n = 8)	Diluted to 5 µg Zn/L
accuracy and precision; repeatability	Mean recovery for certified reference material TM-25.4: Co 228.615 nm: 99.0 ± 2.4 % (n = 12) Zn 213.857 nm: 103.8 ± 3.9 % (n = 16) Co 238.892 nm: 101.2 ± 3.2 % (n = 23)	Diluted to 5.5 µg Co /L 8.9 µg Zn/L
accuracy and precision	Mean recovery for certified reference material TM-25.4: Zn 202.548 nm: 98.9 ± 3.4 % (n = 11)	Diluted to 8.9 µg Zn/L
accuracy and precision; repeatability	Mean recovery for certified reference material TM-53.3: Co 228.615 nm: 100.3 ± 1.5 % (n = 12) Zn 213.857 nm: 100.7 ± 3.2 % (n = 16) Co 238.892 nm: 100.6 ± 2.5 % (n = 23)	Diluted to 25.1 µg Co /L 38.6 µg Zn/L
accuracy and precision	Mean recovery for certified reference material TM-53.3: Zn 202.548 nm: 96.3 ± 1.1 % (n = 11)	Diluted 38.6 µg Zn/L
trueness	recovery of fortified samples: Co: 94.1 – 101.0 % (n = 18) Zn: 94.3 – 101.4 % (n = 16)

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

Sample	Measured conc. [µg Zn/L]	Calculated level after addition [µg Zn/L]	Recovery [µg Zn/L]	Recovery [%]	Measured conc [µg Co/L]	Calculated level after addition [µg Co/L]	Recovery [µg Co/L]	Recovery [%]
1 mL of sample + 4 mL of 50 µg M/L
Sample a from vessel 1 after 2h	4.320	40.864	39.305	96.2	1.295	40.259	38.052	94.5
Sample a from vessel 1 after 6h	7.700	41.540	39.840	95.9	2.167	40.433	38.030	94.1
Sample a from vessel 1 after 24h	8.225	41.645	40.311	96.8	3.614	40.723	38.680	95.0
Sample a from vessel 1 after 96h	2.742	42.548	41.613	97.8	7.387	41.477	40.316	97.2
Sample a from vessel 1 after 168h	16.466	43.293	41.607	96.1	10.558	42.112	40.388	95.9
Sample a from vessel 4 after 336h	21.263	44.253	43.288	97.8	14.016	42.803	41.476	96.9
Sample a from vessel 1 after 505h	23.352	44.670	42.871	96.0	16.354	43.271	41.348	95.6
Sample a from vessel 1 after 672h	24.205	44.841	43.319	96.2	16.884	43.377	41.634	94.5
Sample a from vessel 4 after 168h	197.371	79.474	75.783	95.4	122.448	64.490	62.463	96.9
Sample a from vessel 4 after 336h	191.499	78.300	74.523	95.2	118.969	63.794	61.871	97.0
Sample a from vessel 4 after 504h	190.414	78.083	73.660	94.3	117.785	63.557	61.342	96.5
Sample a from vessel 4 after 672h	187.431	77.486	73.264	94.6	115.570	63.114	60.912	96.5
Sample a from vessel 4 after 6h	111.122	62.224	62.371	100.2	68.722	53.744	51.500	95.8
1 mL of sample + 4 mL 75 µg M/L
Sample a from vessel 4 after 2h	59.345	71.869	72.367	100.7	35.363	67.073	63.859	95.2
1 mL of sample + 4 mL 25 µg M/L

Conclusions:

According to the OECD Series on Testing and Assessment Number 29 (2001), dissolved mean Co, Zn concentrations were determined in a transformation/dissolution test with a loading of 1 mg test item (cobalt zinc silicate blue phenacite) /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
Co [µg/L] 123.59 ± 9.79 12.43 ± 4.02
Zn [µg/L] 201.56 ± 16.88 18.31 ± 7.63
Zn [µg/L] background (means) corrected 193.98 ± 16.88 16.54 ± 5.43

Description of key information

Transformation/dissolution test of cobalt zinc silicate blue phenacite with a loading of 1 mg/L media at 21.5 ± 1.5 °C after 672 h:

- Co: 123.59 ± 9.79 µg/L (pH 6); 12.43 ± 4.02 µg/L (pH 8)

- Zn: 201.56 ± 16.88 µg/L (pH 6); 18.31 ± 7.63 µg/L (pH 8)

- Zn (background (means) corrected): 193.98 ± 16.88 µg/L (pH 6); 16.54 ± 5.43 µg/L (pH 8)

Additional information

According to the OECD Series on Testing and Assessment Number 29 (2001), dissolved mean Co, Zn concentrations were determined in a transformation/dissolution test with a loading of 1 mg test item (cobalt zinc silicate blue phenacite) /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
Co [µg/L]	123.59 ± 9.79	12.43 ± 4.02
Zn [µg/L]	201.56 ± 16.88	18.31 ± 7.63
Zn [µg/L] background (means) corrected	193.98 ± 16.88	16.54 ± 5.43