Vanadium carbide

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012-08-16 to 2013-03-19

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2011-02-07

Type of method:

flask method

Type of test:

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

Mean dissolved conc.:

13.95 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

21.2 °C, pH 7.8

Remarks on result:

other: mean dissolved concentration: 13.95 ± 0.35 µg V/L

Type of test:

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

Mean dissolved conc.:

12.85 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

21.3 °C, pH 6.0

Remarks on result:

other: mean dissolved concentration: 12.85 ± 0.66 µg V/L

Key result

Type of test:

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

Mean dissolved conc.:

21.18 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

21.1 °C, pH 8.0

Remarks on result:

other: mean dissolved concentration: 21.18 ± 1.79 µg V/L

Key result

Type of test:

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

Mean dissolved conc.:

15.68 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

21.5 °C, pH 6.2

Remarks on result:

other: mean dissolved concentrations: 15.68 ± 0.86 µg V/L

Key result

Type of test:

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

Mean dissolved conc.:

41.7 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

21.6 °C, pH 7.7

Remarks on result:

other: mean dissolved concentration: 41.70 ± 4.57 µg V/L

Key result

Type of test:

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

Mean dissolved conc.:

27.84 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

21.4 °C, pH 6.0

Remarks on result:

other: mean dissolved concentration: 27.84 ± 5.90 µg V/L

Details on results:

Measured pHs and oxygen levels as well as mean temperatures of all loadings were in compliance with the requirements of the OECD Series 29. Under the described conditions of this test with vanadium carbide powder at a loading of 1mg/L, dissolved vanadium concentrations were at a
- loading of 1 mg/L V after 7 days 21.18 ± 1.71 μg/L and 15.68 ± 0.96 μg/L at pH 8 and pH 6, respectively,
- loading of 1 mg/L V after 28 days 41.70 ± 4.41 μg/L and 27.84 ± 5.29 μg/L at pH 8 and pH 6, respectively,
- loading of 100 mg/L V after 7 days 4345 ± 155 μg/L and 1288 ± 57 μg/L at pH 8 and pH 6, respectively.

The respective limits of 20% and 10% for the between-vessel and the within-vessel variation, required by OECD Series 29 were met after 7d and 28d.

Method validation summary (ICP-OES)

validation parameter	results	Comment
selectivity	similar data with two different V wavelengths for ICP-OES method	no interferences observed
linearity	applied calibration functions were linear	correlation factor at least 0.998701
limit of detection	1.73 - 20.7µg V/ L
limit of quantification	5.78 68.9 µg V/L
V concentrations in method blanks	Test with 1 mg/L loading: at least below respective LOQs, LOQs ranging from 5.78 – 15.48 µg V/L Test with 100 mg/L loading: below respective LODs, LODs ranging from 7.11 – 8.57 µg V/L
accuracy and precision, reproducibility	mean recovery for CRM TMDA-70 (312 µg V/L): 103.6 ± 0.7 % (n = 6)	concentration range of diluted samples from test with 100 mg/L and samples for mass balance
accuracy and precision, reproducibility	mean recovery for CRM TMDA-70 (156 µg V/L, dilution factor 2): 100.3 ± 2.9 % (n = 7)	concentration range of diluted samples from test with 100 mg/L and samples for mass balance
accuracy and precision, reproducibility	mean recovery for CRM TMDA-70 (31.2 µg V/L, dilution factor 10): 108.4 ± 8.1 % (n = 23)	concentration range of diluted samples
accuracy and precision	mean recovery for Merck XXI (750 µg V/L): 105.4 ± 1.6 % (n = 3)	for high concentration range
accuracy and precision	mean recovery for Merck XXI (250 µg V/L): 99.4 ± 0.7 % (n = 3)	for medium concentration range
accuracy and precision	mean recovery for Merck XXI (100 µg V/L): 104.4 ± 1.8 % (n = 4)	for medium concentration range
accuracy and precision	mean recovery for Merck XXI (50 µg V/L): 109.8 ± 7.1 % (n = 3)	for low concentration range
accuracy and precision, reproducibility	mean recovery for Merck XXI (25 µg V/L): 105.1 ± 10.1 % (n = 17)	for low concentration range
accuracy and precision	mean recovery for recalibration (250 µg V/L): 97.9 ± 1.0 % (n = 4)	for medium concentration range
accuracy and precision, reproducibility	mean recovery for recalibration (100 µg V/L): 100.3 ± 3.0 % (n = 9)	for medium concentration range
accuracy and precision, reproducibility	mean recovery for recalibration (50 µg V/L): 101.7 ± 2.4 % (n = 14)	for low concentration range
accuracy and precision	mean recovery for recalibration (25 µg V/L): 114.2 ± 6.5 % (n = 3)	for low concentration range
accuracy and precision	mean recovery for multielement standard from CPI (500 µg V/L): 101.8 ± 1.2 % (n = 3)	for medium concentration range
accuracy and precision	mean recovery for multielement standard from CPI (250 µg V/L): 95.6 ± 4.5 % (n = 3)	for high concentration range
trueness	Test with 1 mg/L loading:fortification of samples: 99.6 – 101.9 % (n = 4) Test with 100 mg/L loading:fortification of samples: 99.2– 101.1 % (n = 3)

Method validation summary (HPLC-ICP-MS)

validation parameter	results	Comment
selectivity	ICP-MS (^51V) selective for vanadium; chromatographic peaks verified by V(IV) and V(V) standards	no interferences observed
linearity	applied calibration functions were linear	correlation factor at least 0.997
limit of detection	V(IV): 2.0 µg/L V(V): 2.0 µg/L
limit of quantification	V(IV): 6.1 µg/L V(V): 6.0 µg/L
method blanks	At least below LOQ for V(IV) and V(V)
accuracy and precision, reproducibility	mean recovery for recalibration standards (50 µg/L V(IV) and 50 µg/L V(V)): Test with loading of 1 mg/L: 94.9 ± 11.1 % (n = 30) for V(IV) 94.4 ± 9.9 % (n = 30) for V(V)	concentration range of samples (QA/QC requirements 100 ± 25 %)
accuracy and precision	mean recovery for recalibration standards (50 µg/L V(IV) and 50 µg/L V(V)): Test with loading of 100 mg/L: 88.0 ± 15.9 % (n = 3) for V(IV) 85.7 ± 15.3 % (n = 3) for V(V)
accuracy and precision	mean recovery for recalibration standards (100 µg/L V(IV) and 100 µg/L V(V)): Test with loading of 100 mg/L: 97.2 ± 6.3 % (n = 3) for V(IV) 95.4 ± 6.7 % (n = 3) for V(V)	concentration range of samples (QA/QC requirements 100 ± 25 %)
accuracy and precision, reproducibility	mean recovery for recalibration standards (200 µg/L V(IV) and 200 µg/L V(V)): Test with loading of 100 mg/L: 123.2 ± 2.1 % (n = 5) for V(IV) 122.6± 3.2 % (n = 5) for V(V)	concentration range of samples (QA/QC requirements 100 ± 25 %)
accuracy and precision, reproducibility	mean recovery for recalibration standards (500 µg/L V(IV) and 500 µg/L V(V)): Test with loading of 100 mg/L: 102.1 ± 5.7 % (n = 8) for V(IV) 99.9 ± 10.3 % (n = 8) for V(V)	concentration range of samples (QA/QC requirements 100 ± 25 %)
trueness	total V (by ICP-OES) compared to sum of V(IV) and V(V) (by HPLC-ICP-MS): Test with loading of 1 mg/L at pH 6: recoveries are in the range of 86.8% to 112.6 % Test with loading of 1 mg/L at pH 8: recoveries are in the range of 84.7 % to 100.8 % Test with loading of 100 mg/L at pH 6: recoveries are in the range of 82.4 % to 102.9 % Test with loading of 100 mg/L at pH 8: recoveries are in the range of 83.6 % to 93.7 %	Quality requirements are 100 ± 25% due to comparison of two methods with very different uncertainties

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 vessels with a loading of 1 mg/L at pH 6 and pH 8 are in compliance with the test guidance for the tested loadings at pH 6 and pH 8 after 7 and 28 days, respectively.

Conclusions:

In a transformation/dissolution test according to OECD Series # 29 with vanadium carbide at a loading of 1 mg/L, dissolved vanadium concentrations after 28 days amount to 41.70 μg/L and 27.84 μg/L at pH 8 and pH 6, respectively. The dissolved vanadium concentrations at a loading of 1 mg/L at pH 8 and pH 6 after 7 days were 21.18 μg/L and 15.68 µg/L, respectively. Thus, the vanadium release in environmental media was higher at pH 8 than the release at pH 6. During the T/D tests, predominantly pentavalent vanadium species were detected.

Reference 2

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

yes

Remarks:

See "Principles of method if other than guideline"

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

yes

Remarks:

See "Principles of method if other than guideline"

Principles of method if other than guideline:

- Based on experience and in view of the poor solubility of other metal substances (e.g. metal carbonates), the test was conducted under exclusion of atmospheric carbon dioxide and oxygen.
- Two vessels were set up in a parallel design at 20 ± 1.0 °C, each solution was sampled repeatedly over time instead of setting up multiple vessels and sampling solutions from a different vessel at each sampling date. This modification helps to minimize weighing errors as larger amounts are being handled.

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2011-02-07

Type of method:

flask method

Water solubility:

1 754.89 µg/L

Conc. based on:

element (dissolved fraction)

Remarks:

Vandium

Loading of aqueous phase:

200 mg/L

Incubation duration:

>= 1 - <= 3 d

Temp.:

20.3 °C

pH:

5.2

Remarks on result:

other: SD = 149.44 µg/L

Key result

Water solubility:

2 114.3 µg/L

Conc. based on:

test mat. (dissolved fraction)

Loading of aqueous phase:

200 mg/L

Incubation duration:

>= 1 - <= 3 d

Temp.:

20.3 °C

pH:

5.2

Remarks on result:

other: calculated based on a V content of 83 %, SD = 180.0 µg/L

Details on results:

Observations:
During the study, undissolved test material was observed in solution, at the wall and bottom of the flask. After filtration and centrifugation, solutions were clear.

Temperature
The temperature was monitored using a Testo Data Logger. The mean temperature was 20.1 ± 0.2 °C.

Oxygen concentration
During the experimental performance of the test, the oxygen concentration in the acrylic glass box was measured with a MICRO IV oxygen sensor prior the test and directly before and after each sampling. The oxygen concentration (in %) remained around 0 %. Slightly negative values, though impossible, are due to measurement uncertainties of the device at 0 % oxygen.

Solution pH
Solution pH in samples containing the test item ranged from 5.1 - 5.2. Measured pH in method blanks ranged from 6.3 to 6.6.

Turbidity
The turbidity was measured after filtration and centrifugation to verify that only dissolved vanadium concentrations would get measured. The turbidity was always <<1 NTU, indicating that there was not any undissolved material after the filtration step.

Dissolved vanadium concentrations
Due to potential contaminations of the electrodes for pH measurements and because of very low limits of detection vanadium levels in method blanks were above the limits of quantification (LOQ = 0.114 - 0.546 µg V/L) but far below concentrations in diluted actual samples (<< 1 %).
Test samples were diluted (dilution factor 10) so that the respective vanadium concentrations would be in the calibrated range of the ICP-OES instrument. Constant vanadium concentrations as defined by study guideline OECD 105 and Regulation 440/2008/EC A.6 were measured during the first three days of testing.

Method validation summary

validation parameter	results	comment
selectivity	similar data with at least two different vanadium wavelengths for ICP-OES method	no interferences due to test media observed
linearity	applied calibration functions were linear	correlation coefficient at least 0.999843
limits of detection (LOD)	0.038 – 0.182 µg V/L
limits of quantification (LOQ)	0.114 - 0.546 µg V/L
method blanks	above LOQ but far below conc. in diluted actual samples (<< 1 %).	-
accuracy and precision, repeatability	mean recovery for TMDA-70 (dilution factor 10, 31.2 µg V/L): 100 ± 1 % (n = 6)	for low concentration range of diluted samples and for fortification and method blanks
accuracy and precision, repeatability	mean recovery for TM-15.2 (13.1 µg V/L): 100.6 ± 0.9 % (n = 6)	for low concentration range for fortification and method blanks
accuracy and precision	mean recovery for Merck XXI standard (100 µg V/L): 99.6 ± 1.5 % (n = 6)	for low concentration range
trueness	recovery from fortification of samples: 99.5 - 101 % (n = 4)

Results

Table: Measured vanadium concentrations in test samples (internal calculations were performed with more digits, values were rounded)

test day [d]	V conc. of samples vessel 1 [mg/L]	mean V conc. ± SD vessel 1 [mg/L]	V conc. of samples vessel 2 [mg/L]	mean V conc. ± SD vessel 2 [mg/L]	mean V conc. ± SD [mg/L]	variation between samplings [%]
1	1.59	1.55 ± 0.05	1.63	1.63 ± <0.01	1.59 ± 0.05
	1.52		1.63
2	1.73	1.73 ± 0.01	1.74	1.76 ± 0.02	1.74 ± 0.02	9.52
	1.72		1.77
3	1.93	1.93 ± <0.01	1.94	1.93 ± 0.01	1.93 ± <0.01	11.0
	1.93		1.93

Table: Measured vanadium concentrations in method blanks

test day [d]	V conc. blank 1 [µg/L]	V conc. blank 2 [µg/L]	LOD [µg V/L]	LOQ [µg V/L]
1	1.69	1.81	0.182	0.546
	1.51	1.52
2	1.37	1.45
	1.58	1.29
3	2.20	2.24
	2.23	2.23

Constant vanadium concentrations were measured during the first three days of testing, i.e. vanadium concentrations varied by less than 15 % between sampling points. Therefore, the acceptability criteria of the study guideline OECD 105 and Regulation 440/2008/EC A.6 could be regarded as fulfilled. The mean dissolved vanadium concentrations of solutions sampled on day 1, day 2 and day 3 were calculated.

Mean dissolved V concentrations day 1 – day 3:

Vessel 1: 1.74 ± 0.17 mg/L

Vessel 2: 1.77 ± 0.14 mg/L

The amount of dissolved vanadium carbide was calculated based on the vanadium content of the test substance as follows:

= mean of measured V concentration * 100 % / 83 % [V content of test item]

mean calculated dissolved vanadium carbide, day 1 – day 3:

Vessel 1: 2.09 ± 0.21 mg/L

Vessel 2: 2.14 ± 0.17 mg/L

Conclusions:

Under the conditions of this test (under exclusion of CO2 and O2, under inert argon gas; flask method; loadings of 200.004 and 200.002 mg/L in vessel 1 and 2, respectively), a solubility equilibrium was reached during the first three days of testing. The mean measured amount of dissolved V on day 1, day 2 and day 3 at 20.0 ± 1.0°C is 1.75 ± 0.15 mg/L (determined as dissolved V, separated by filtration and subsequent centrifugation from undissolved test item). This corresponds to a water solubility of dissolved vanadium carbide of 2.11 ± 0.18 mg/L, calculated based on a vanadium content of 83 %. Solution pH in samples containing the test item remained at 5.1 - 5.2 while the pH in method blanks ranged from 6.3 to 6.6. Hence, vanadium carbide is considered as slightly soluble (0.1-100 mg/L)

Description of key information

The solubility of vanadium carbide powder in water based on testing according to OECD 105 at a loading of 200 mg/L is estimated based on vanadium release with 2.11 mg/L at 20 °C and pH 5.2.

Regarding the transformation/dissolution of vanadium carbide in environmental media according to OECD Series 29, measured dissolved vanadium concentrations at 1 mg/L loading and pH 8 and pH 6 amount to 21.18 μg/L and 15.68 μg/L after 7 days and 41.70 µg/L and 27.84 µg/L after 28 days, respectively.

Key value for chemical safety assessment

Water solubility:

2.11 mg/L

at the temperature of:

20 °C