Sodium metavanadate

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2013-03-18 to 2013-04-05

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:

Modifications to OECD 105:
(i) The test was conducted under exclusion of atmospheric carbon dioxide and atmospheric oxygen.
(ii) 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:

89.3 g/L

Conc. based on:

element (dissolved fraction)

Remarks:

Vanadium

Loading of aqueous phase:

1 000 other: g test item /L

Incubation duration:

>= 1 - <= 3 d

Temp.:

20 °C

pH:

9.5

Remarks on result:

other: SD: 2.03 g/L

Water solubility:

225.2 g/L

Conc. based on:

test mat. (dissolved fraction)

Remarks:

Sodium metavanadate

Loading of aqueous phase:

1 000 g/L

Incubation duration:

>= 1 - <= 3 d

Temp.:

20 °C

pH:

9.5

Remarks on result:

other: calculated sodium metavanadate based on a vanadium content of 39.65 % / SD: 5.1 g/L

Details on results:

Observations
During the study, a bulk of undissolved test material was observed in solution and especially on the bottom of the flasks. After filtration, the solution was clear. Due to a limited sampling turbidity measurement was only performed once, to verify that only dissolved vanadium concentrations would get measured. The turbidity was measured in a filtered sample directly after sampling.

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

Monitoring 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 clearly increased to 9.4 – 9.6, pHs in method blanks ranged from 6.3 to 6.6.

Turbidity
The turbidity was measured after filtering 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 limit of quantification (LOQ = 0.546 µg V/L) but far below concentrations in diluted actual samples (< 0.3 %).
Test samples were diluted (dilution factor 100,000) so that the respective vanadium concentrations would be in the calibrated range of the ICP-OES instrument. Constant vanadium concentrations as defined by the 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 0.999746
limits of detection (LOD)	0.182 – 0.229 µg V/L
limits of quantification (LOQ)	0.546 – 0.686 µg V/L
method blanks	above LOQ (LOQ = 0.546 µg V /L), but far below conc. in diluted actual samples (< 0.3 %).
accuracy and precision	mean recovery for TMDA-70 (312 µg V/L): 98.9 ± 0.2 % (n = 3)	for concentration range of diluted samples
accuracy and precision	mean recovery for TMDA-70 (dilution factor 10, 31.2 µg V/L): 100 ± 1 % (n = 4)	for low concentration range of diluted samples for fortification and method blanks
accuracy and precision	mean recovery for TM-15.2 (13.1 µg V/L): 101 ± 1 % (n = 4)	for low concentration range for fortification and method blanks
accuracy and precision	recovery for recalibration standard (750 µg V/L): 99.1 ± 0.5 % (n = 2)	for concentration range of diluted samples
accuracy and precision	mean recovery for Merck XXI standard (100 µg V/L): 100 ± 2 % (n = 4)	for low concentration range
trueness	recovery from fortification of samples: 97.6 - 98.5 % (n = 4)
repeatability	mean recovery for TMDA-70 (dilution factor 10, 31.2 µg V/L): 100 ± 1 % (n = 4)	for low concentration range of diluted samples for fortification and method blanks
repeatability	mean recovery for TM-15.2 (13.1 µg V/L): 101 ± 1 % (n = 4)	for low concentration range for fortification and method blanks
repeatability	mean recovery for Merck XXI standard (100 µg V/L): 100 ± 2 % (n = 4)	for low concentration range

Results

Dissolved V concentrations were measured by ICP-OES. Samples from each vessel at each sampling point were measured in duplicate. Based on pre-test data (non-GLP), 70g (70.0005g, 70.0004g in vessel A and B, respectively) of the test substance and 70 mL of ultrapure water were added into each test flask. The applied loading corresponds to at least five times the quantity of the measured water solubility, in compliance with the OECD guideline. Furthermore, an undissolved residue was observed in the test vessels during the test.

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 from day 1 until day 3 were calculated.

Mean dissolved V concentrations day 1 – day 3:

Vessel A: 88.72 ± 1.36 g/L

Vessel B: 89.90 ± 2.52 g/L

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

 = mean of measured V concentration * 100 % / 39.65 % [V content of test item]

 

mean calculated ammonium sodium vanadium oxide dissolved day 1 – day 3:

Vessel A: 223.8 ± 3.4 g/L

Vessel B: 226.7 ± 6.4 g/L

Final resultsUnder the conditions of this test (under exclusion of CO2 and O2, under inert argon gas; flask method; loadings of 1000.0071 and 1000.0057 g/L in vessel A and B, respectively), a solubility equilibrium was reached during the first three days of testing. The mean measured amount of dissolved V from day 1 until day 3 at 20.0 ± 1.0 °C is 89.31 ± 2.03 g/L (determined as dissolved V, separated by filtration from undissolved test item). This corresponds to a water solubility of dissolved sodium meta vanadate of 225.2 ± 5.1 g/L, calculated based on a vanadium content of 39.65 %. Solution pH in samples containing the test item clearly increased to 9.4 – 9.6. Measured pH in method blanks ranged from 6.5 to 6.7.

Conclusions:

Under the conditions of this test (under exclusion of CO2 and O2, under inert argon gas; flask method; loadings of 1000.0071 and 1000.0057 g/L in vessel A and B, respectively), a solubility equilibrium was reached during the first three days of testing. The mean measured amount of dissolved V from day 1 until day 3 at 20.0 ± 1.0°C is 89.31 ± 2.03 g/L (determined as dissolved V, separated by filtration from undissolved test item). This corresponds to a water solubility of dissolved sodium metavanadate of 225.2 ± 5.1 g/L, calculated based on a vanadium content of 39.65 %. Solution pH in samples containing the test item increased to a pH of 9.4 – 9.6 while the pH of method blanks ranged from 6.5 to 6.7. Hence, sodium metavanadate may considered as very soluble (> 10000 mg/L).

Reference 2

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2011-05-19 to 2011-09-14

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:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed on 2011-02-07

Type of method:

flask method

Type of test:

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

Mean dissolved conc.:

365 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

1 d

Test conditions:

pH 8; 21.0 °C

Remarks on result:

other: SD: ± 13 µg V/L

Type of test:

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

Mean dissolved conc.:

382 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

1 d

Test conditions:

pH 6, 21.0 °C

Remarks on result:

other: SD: ± 13 μg V/L

Key result

Type of test:

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

Mean dissolved conc.:

300 µg/L

Element analysed:

vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 8, 21.7 °C

Remarks on result:

other: S.D: ± 13 µg V/L

Key result

Type of test:

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

Mean dissolved conc.:

309 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6, 20.9 °C

Remarks on result:

other: S.D: ± 13 µg V/L

Key result

Type of test:

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

Mean dissolved conc.:

263 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 8, 21.0 °C

Remarks on result:

other: SD: ± 12 μg V/L

Key result

Type of test:

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

Mean dissolved conc.:

267 µg/L

Element analysed:

Vanadium

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6, 21.0 °C

Remarks on result:

other: SD: ± 8 μg V/L

Details on results:

Measured concentrations indicate a complete dissolution of the test item in both media. Over the course of the test, only pentavalent vanadium species were detected. The mean vanadium concentrations in solutions after 24h were 365 ± 13 μg V/L and 382 ± 13 μg V/L at a loading of 1 mg/L at pH 8 and 6, respectively.

The mean vanadium concentrations in solutions after 28 d were 263 ± 12 μg V/L and 267 ± 8 μg V/L at a loading of 1 mg/L at pH 8 and 6, respectively. Sodium metavanadate was completely dissolved after 2 hours in both media (pH 6 & pH 8). The decrease of measured vanadium concentrations over time is due to dilution, i.e. removal of vanadium by sampling and replacing the sampled test media (i.e., 150 ml fresh media after 24h and respectively 50 mL at every subsequent sampling) in accordance with the guidance document.

Normalizing dissolved V concentrations for vanadium removed by sampling indicates that at any sampling time, all vanadium in the test vessels was completely dissolved. Recovery of total dissolved vanadium expressed as the sum of measured dissolved tetra- and pentavalent vanadium species ranged from 79.6 to 101%.

The within and between vessel variation, the variation of mean V concentrations between sampling intervals as well as pH, temperature and oxygen levels meet the requirements of the OECD-Guidance document 29.

Conclusions:

Under the described conditions of this test with sodium metavanadate at a loading of 1 mg/L, dissolved vanadium concentrations after 28 days were 263 ± 12 μg/L and 267 ± 8 μg/L at pH 8 and pH 6, respectively. Measured concentrations indicate a complete dissolution of sodium metavanadate at pH 8 and pH 6.

Description of key information

Water solubility: 225.2 ± 5.1 g/L at 20 °C and pH 9.4 -9.6 (exclusion of CO2 and O2, under inert argon gas)

Transformation / dissolution: 263 ± 12 μg/L at pH 8 and 267 ± 8 μg/L at pH 6

Key value for chemical safety assessment

Water solubility:

225.2 g/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 1000.0071 and 1000.0057 g/L in vessel A and B, respectively), a solubility equilibrium was reached during the first three days of testing. The mean measured amount of dissolved V from day 1 until day 3 at 20.0 ± 1.0 °C is 89.31 ± 2.03 g/L (determined as dissolved V, separated by filtration from undissolved test item). This corresponds to a water solubility of dissolved sodium metavanadate of 225.2 ± 5.1 g/L, calculated based on a vanadium content of 39.65 %. Solution pH in samples containing the test item clearly increased to 9.4 – 9.6. Measured pH in method blanks ranged from 6.5 to 6.7.

Transformation / dissolution

In a transformation dissolution test with sodium metavanadate at a loading of 1 mg/L, dissolved vanadium concentrations after 28 days were 263 ± 12 μg/L and 267 ± 8 μg/L at pH 8 and pH 6, respectively. Measured concentrations indicate a complete dissolution of the test item in both media.