Divanadium tris(sulphate)

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2013-03-05 to 2013-06-20

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:

- exclusion of CO2, O2 - two vessels were set up in a parallel design, instead of setting up multiple vessels and sampling

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

yes

Remarks:

- exclusion of CO2, O2 - two vessels were set up in a parallel design, instead of setting up multiple vessels and sampling

GLP compliance:

yes (incl. QA statement)

Remarks:

signed, 2011-02-07

Type of method:

flask method

Water solubility:

82.79 g/L

Conc. based on:

element (dissolved fraction)

Remarks:

Vanadium

Loading of aqueous phase:

1 300 g/L

Incubation duration:

>= 1 - <= 3 d

Temp.:

20 °C

pH:

< 0

Remarks on result:

other: mean dissolved concentration: 82.79 ± 2.17 g V/L

Key result

Water solubility:

660.2 g/L

Conc. based on:

test mat. (dissolved fraction)

Loading of aqueous phase:

1 300 g/L

Incubation duration:

>= 1 - <= 3 d

Temp.:

20 °C

pH:

< 0

Remarks on result:

other: mean dissolved divanadium (tris)sulphate: 660.17 ± 17.29 g/L

Details on results:

Observations
During the study, undissolved test material was observed in solution and especially on the bottom of the flasks. After filtration, the solution was clear.

Temperature
The temperature in the thermostatically controlled water bath was monitored by a Testo 175-T2 thermo datalogger. The mean temperature was 20.3 ± 0.1 °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 ranged from -1.0 to -0.4 %. Slightly negative values, though impossible, are due to measurement uncertainties of the device at 0 % oxygen content.

Solution pH
Solution pH of samples containing the test item decreased to – 0.8. The measured pH of method blanks ranged from 6.1 to 6.2.

Turbidity
The turbidity was measured after filtration to verify that only dissolved vanadium concentrations would get measured. The turbidity was always < 1 NTU, indicating that there was not any undissolved material and micelles did not form after the filtration step. Method blanks were only filtered and not centrifuged, because the turbidity measurements were always < 1 NTU.

Dissolved vanadium concentrations
Vanadium levels of all method blanks were at least below the limit of quantification (LOQ = 4.47 µg V/L).
The pH of the test solution was much lower at the higher loading of the main test, and the lower solution pH may have enhanced the dissolution. However, an insoluble residue was observed in the test vessels after 3 days. The consistent V concentrations and observed precipitation to indicate that the solubility equilibrium had been reached.
Vanadium concentrations remained constant during the first three days of testing as defined by the study guideline OECD 105 and Regulation 440/2008/EC A.6.

Method validation summary

validation parameter	results	comment
selectivity	similar data with at least two different wavelengths for ICP-OES method	no interferences due to test media observed
linearity	applied calibration functions were linear	correlation coefficient at least 0.999973
limits of detection (LOD)	1.34 - 1.49 µg V/L
limits of quantification (LOQ)	4.03 - 4.47 µg V/L
V concentrations in method blanks	At least below respective LOQ (< 4.47 µg V /L)	-
accuracy and precision; repeatability	mean recovery for TMDA-70 (dilution factor 10: 31.2 µg V/L): 96.4 ± 4.2 (n = 6)	concentration range of diluted samples
accuracy and precision; repeatability	mean recovery for TM-15.2 (13.1 µg V/L): 109.5 ± 2.3 (n = 6)	low concentration range
accuracy and precision; repeatability	mean recovery for Merck XXI standard (100 µg V/L): 99.7 ± 1.5 (n = 6)	concentration range of diluted samples
trueness	recovery of fortified samples: 100.4 – 102.4 %

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 and the observed precipitation 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 A: 83.37 ± 1.78 g/L

Vessel B: 82.20 ± 2.52 g/L

The amount of dissolved divanadium (tris)sulphate was calculated based on the measured vanadium content of the test substance as follows:

 = mean of measured V concentration * 100 % / 12.54 % [V content of test item]

 

mean dissolved divanadium (tris)sulphate on day 1, 2 and3:

Vessel A: 664.8 ± 14.2 g/L

Vessel B: 655.5 ± 20.1 g/L

Final results

Under the conditions of this test(under exclusion of CO2 and O2, under inert argon gas; flask method; a loading of 1300 g/L), 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 82.79 ± 2.17 g/L (determined as dissolved V, separated by filtration from undissolved test item). This corresponds to a water solubility of dissolved divanadium (tris)sulphate of 660.2 ± 17.3 g/L, calculated based on a vanadium content of 24.8 %. Solution pH of samples containing the test item decreased to – 0.8 whereas the measured pH of method blanks remained at 6.1 to 6.2.

Conclusions:

Under the conditions of this test (under exclusion of CO2and O2, under inert argon gas; flask method; a loading of 1300 g/L), 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 82.79 ± 2.17 g/L (determined as dissolved V, separated by filtration from undissolved test item). This corresponds to a water solubility of dissolved divanadium (tris)sulphate of 660.2 ± 17.3 g/L, calculated based on a vanadium content of 24.8 %. Solution pH of samples containing the test item decreased to – 0.8 whereas the measured pH of method blanks remained at 6.1 to 6.2. Hence, divanadium (tris)sulphate may considered as very soluble (> 10000 mg/L).

Description of key information

The water solubility of divanadium trisulphate is 660.2 ± 17.3 g/L at pH -0.8 and 20 °C.

Key value for chemical safety assessment

Water solubility:

660.2 g/L

at the temperature of:

20 °C