Vanadium carbide nitride (V(C,N))

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:

2012-11-12 2013-01-24

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.:

1.03 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

1 d

Test conditions:

22.3 °C, pH 6.2

Remarks on result:

other: S.D: ± 0.498 µg V/L

Key result

Type of test:

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

Mean dissolved conc.:

1.786 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

21.6 °C, pH 6.2

Remarks on result:

other: S.D: ± 0.630 µg V/L

Key result

Type of test:

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

Mean dissolved conc.:

1.638 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

21.5 °C, pH 6.2

Remarks on result:

other: S.D: ± 0.188 µg V/L

Type of test:

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

Mean dissolved conc.:

1.119 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

1 d

Test conditions:

22.3 °C, pH 7.8

Remarks on result:

other: S.D: ± 0.663 µg V/L

Key result

Type of test:

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

Mean dissolved conc.:

1.877 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

21.5 °C, pH 7.8

Remarks on result:

other: S.D: ± 0.578 µg V/L

Key result

Type of test:

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

Mean dissolved conc.:

1.706 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: S.D: ± 0.508 µg V/L

Details on results:

Temperature
The mean temperature was 21.3 ± 0.6 °C during the 28 days of testing and in agreement with the OECD guidance document 29.

Solution pH and oxygen concentrations
In solutions containing 1 mg/L of the test item and in respective method blanks at pH 6 and 8, pH ranged from 6.1 – 6.3 and 7.7 – 7.9, respectively.
Oxygen levels in all test vessels (all loadings) were in compliance with the requirements of the OECD Test Guidance 29 during the test, i.e. above 70 % of oxygen saturation at 8.5 mg/L (70 % of 8.5 mg/L = 6 mg/L)

Analytical measurements:
Observed between-vessel variation after 28 days is less than 20 % and is thus in accordance with OECD series on testing and assessment 29. However, observed within-vessel variation after 28 days is not always < 10 % as recommended by the guidance, which may be explained by the low vanadium levels in solution.
Mass balance
Samples were taken from solutions after adding aqua regiato dissolve the test residues. Dissolved vanadium was measured by ICP-OES and the mass balance was calculated considering the replacement of sampling solution after each sampling by adding blank test media (120 mL after 24 h and 40 mL after each sampling). The filters used for sampling were extensively rinsed with an exact amount ofaqua regiaand vanadium concentrations in the filtrate were determined. Concentrations in the filtrates were below the respective LOD/LOQ (1.10 µg V/L / 3.29 µg V/L). Therefore, these amounts were not considered for calculation.

The nominal amount of vanadium was calculated by:
Added test item (mg) * 78.19 (percentage of V in VCN) / 100

Vanadium recoveries ranged from of 1.3 to 22.7 %, clearly showing that the test substance is nearly insoluble (sparingly soluble), even after 12 h inaqua regia. However, different recoveries indicate that aqua regia dissolves the test item but 12 h may not be sufficient to dissolve 1 mg under these acidic conditions.

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 0.999627
limit of detection	0.152 – 0.414 µg V/L
limit of quantification	0.456 – 1.24 µg V/L
V concentrations in method blanks	Above LOQ of respective measurement series mainly due to background of test media media. Potential cross-contamination during measurements withelectrodes cannot be completely excluded.	-
accuracy & precision	mean recovery for CRM TMDA-70 (31.2 μg V/L, dilution factor 10): 94.7 ± 2.0 % (n = 3)	concentration range of mass balance samples
accuracy & precision, repeatability	mean recovery for CRM TMDA-70 (7.8 μg V/L, dilution factor 40): 103.0 ± 5.4 % (n = 10)	concentration range
accuracy & precision	mean recovery for recalibration (25 µg V/L): 92.8 ± 1.1 % (n = 3)	concentration range of mass balance samples
accuracy & precision, repeatability	mean recovery for recalibration (5 μg V/L): 98.0 ± 3.2 % (n = 9)	concentration range
accuracy & precision	mean recovery for quality control standard (50 μg V/L): 95.7 ± 0.8 % (n = 3)	concentration range of mass balance samples
accuracy & precision, repeatability	mean recovery for quality control standard (5 μg V/L): 96.3 ± 5.6 % (n = 9)	concentration range
trueness	fortification of samples: 88.6 – 93.3 % (n = 4)

Results:

In solutions containing 1 mg/L of the test item and in respective method blanks at pH 6 and 8, pH ranged from 6.1 – 6.3 and 7.7 – 7.9, respectively.

Oxygen levels in all test vessels (all loadings) were in compliance with the requirements of the OECD Test Guidance 29 during the test, i.e. above 70 % of oxygen saturation at 8.5 mg/L (70 % of 8.5 mg/L = 6 mg/L).

Conclusions:

Under the described conditions of this transformation/dissolution test (OECD Series on Testing and Assessment Number 29, 2001) with vanadium carbide nitride at a loading of 1 mg/L, dissolved vanadium concentrations after 28 d at pH 8 and pH 6 amount to 1.71 µg/L and 1.64 µg/L, respectively. Dissolved vanadium concentrations after 7 d at pH 8 and pH 6 amount to 1.88 µg/L and 1.79 µg/L, respectively.

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:

Two vessels were set up in a parallel design, each vessel was sampled several times instead of sampling one vessel every time or using individual vessels sampled only once. This modification helps avoiding weighing errors and enables more samplings.

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

yes

Remarks:

Two vessels were set up in a parallel design, each vessel was sampled several times instead of sampling one vessel every time or using individual vessels sampled only once. This modification helps avoiding weighing errors and enables more samplings.

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

Remarks:

analysis via ICP-OES

Water solubility:

3.33 µg/L

Conc. based on:

element (dissolved fraction)

Remarks:

Vanadium

Loading of aqueous phase:

10 mg/L

Incubation duration:

>= 1 - <= 3 d

Temp.:

20 °C

pH:

>= 6.8 - <= 6.9

Remarks on result:

other: S.D: ± 0.30 μg V /L

Water solubility:

4.25 µg/L

Conc. based on:

test mat. (dissolved fraction)

Loading of aqueous phase:

10 mg/L

Incubation duration:

>= 1 - <= 3 d

Temp.:

20 °C

pH:

>= 6.8 - <= 6.9

Remarks on result:

other: calculated water solubility of VCN based on a V content of 78.19 %, S.D: ± 0.38 μg/L

Details on results:

Observations
During the study, undissolved test material was observed in solution. After filtration, the solution was clear as confirmed by turbidity measurements

Temperature
The temperature was monitored using a Testo Data Logger. The mean temperature was 20.7 ± 0.3 °C.

Monitoring oxygen concentration
The oxygen concentration remained around 0 %. Slightly negative values, though impossible, are due to measurement uncertainties of the device at 0 % oxygen.

Solution pH
The solution pH in samples containing the test item remained at 6.8 – 6.9, the pH in method blanks was 6.2

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

Dissolved vanadium concentrations
Dissolved vanadium concentrations in method blanks sampled at each time point were below the limit of quantification

Method validation summary

validation parameter	results	comment
selectivity	Comparable data at two different wavelengths of ICPOES data at 292.401 nm were applied	matrix effects were not observed
linearity	applied calibration function was linear	Correlation coefficient was 0.999647
limits of detection (LOD)	0.235 μg V/L
limits of quantification (LOQ)	0.706 μg V/L
V concentrations in method blanks	At least below respective LOQ (< 0.706 μg V /L)
accuracy and precision; repeatability	mean recovery for TMDA-70 (dilution factor 10, 31.2 μg V/L): 101.3 ± 5.9 (n = 4)
accuracy and precision; repeatability	mean recovery for recalibration (50 μg V/L): 104.0 ± 1.1 (n = 4)
accuracy and precision; repeatability	mean recovery for Merck XXI standard (25 μg V/L): 107.5 ± 5.4 (n = 4)
trueness	recovery of fortified samples: 99.2 – 102.1 %

Results

Vanadium concentrations remained constant during the first three days of testing, i.e. vanadium concentrations varied by less than 15 % between sampling points. Thus, measured V concentrations indicate that a solubility equilibrium had been reached and the test was terminated after 3 days. Therefore, the acceptability criteria of the study guideline OECD 105 and Regulation 440/2008/EC A.6 were fulfilled.

The mean dissolved vanadium concentrations of solutions sampled on day 1, 2 and 3 amount to:

Vessel 1: 3.20 ± 0.19 μg/L

Vessel 2: 3.45 ± 0.35 μg/L

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

= mean of measured V concentration * 100 % / 78.19 % [V content of test item]

mean dissolved vanadium carbide nitride on day 1, 2 and 3:

Vessel 1: 4.09 ± 0.45 μg/L

Vessel 2: 4.42 ± 0.38 μg/L

Conclusions:

Under the conditions of this test (under exclusion of CO2 and O2, under inert argon gas; flask method; loadings of 9.998 and 10.006 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, 2 and 3 at 20.0 ± 1.0°C is 3.33 ± 0.30 μg V /L (determined as dissolved V, separated by filtration from undissolved test item). This corresponds to a water solubility of vanadium carbide nitride powder of 4.25 ± 0.38 μg/L, calculated based on a vanadium content of 78.19 %. Solution pH of samples containing the test item remained at 6.8 - 6.9, the pH of method blanks stayed at 6.2.

Description of key information

The water solubility of vanadium carbide nitride powder is 4.25 µg/L at 20.0 ± 1.0 °C and pH 6.8 – 6.9.

Key value for chemical safety assessment

Water solubility:

4.25 µg/L

at the temperature of:

20 °C

Additional information

water solubility:

Under the conditions of this test (under exclusion of CO2 and O2, under inert argon gas; flask method; loadings of 9.998 and 10.006 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, 2 and 3 at 20.0 ± 1.0°C is 3.33 ± 0.30 μg V /L (determined as dissolved V, separated by filtration from undissolved test item). This corresponds to a water solubility of vanadium carbide nitride powder of 4.25 ± 0.38 μg/L, calculated based on a vanadium content of 78.19 %. Solution pH of samples containing the test item remained at 6.8 - 6.9, the pH of method blanks stayed at 6.2.

Transormation/dissolution:

Under the described conditions of this transformation/dissolution test (OECD Series on Testing and Assessment Number 29, 2001) with vanadium carbide nitride at a loading of 1 mg/L, dissolved vanadium concentrations after 28 d at pH 8 and pH 6 amount to 1.71 µg/L and 1.64 µg/L, respectively. Dissolved vanadium concentrations after 7 d at pH 8 and pH 6 amount to 1.88 µg/L and 1.79 µg/L, respectively.