Zirconium propionate

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2013-04-15 to 2013-05-07

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

yes

Remarks:

two vessels were set up in a parallel design at 20 ± 1.0 °C, each vessel was sampled several times instead of sampling one vessel at every point in time

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

yes

Remarks:

two vessels were set up in a parallel design at 20 ± 1.0 °C, each vessel was sampled several times instead of sampling one vessel at every point in time

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2011-02-07

Type of method:

flask method

Remarks:

analysis via ICP-OES

Water solubility:

58 mg/L

Conc. based on:

element (dissolved fraction)

Remarks:

Zr

Loading of aqueous phase:

20 g/L

Incubation duration:

9 d

Temp.:

20 °C

pH:

>= 4.1 - <= 4.2

Remarks on result:

other: dissolved Zr from day 8 until day 9 at a loading of ca. 20 g zirconium propionate /L

Water solubility:

246.8 mg/L

Conc. based on:

test mat.

Loading of aqueous phase:

20 g/L

Incubation duration:

9 d

Temp.:

20 °C

pH:

>= 4.1 - <= 4.2

Remarks on result:

other: calculated dissolved zirconium propionate from day 8 until day 9 at a loading of ca. 20 g/L

Details on results:

Observations
During the study, undissolved test material was observed in the media in the flasks. After filtration, the solutions were clear. In order to verify this, the turbidity was measured in filtered samples.

Temperature
The temperature in the thermostatically controlled water bath was monitored by a Testo 175-T2 thermo datalogger. The tempearture was 20.6 ± 0.2 °C.

Monitoring oxygen concentration
During the experimental performance of the test, the oxygen concentration in the acrylic glass box was monitored with a MICRO IV oxygen sensor prior and after sampling. The oxygen values (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 method blanks ranged from 5.5 to 6.2, whereas the pH in test item containing vessels were 4.1 – 4.2. The temperature measured by the pH meter is not within 20.0 ± 1.0 °C. Considering the pH values the pH meter is calibrated every workweek and verified every working day. A calibration of the temperature was not performed because a Testo 175-T2 thermo data logger was applied during the test.

Turbidity
The turbidity was measured after centrifugation and filtration to verify that only dissolved calcium 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 and centrifugation step. Method blanks were only filtered and not centrifuged, because the turbidity measurements were always < 1 NTU.

Dissolved zirconium concentrations
Dissolved zirconium concentrations in method blanks from days 1, 2, 3 and 8 were at least below the respective limits of quantification (LOQ = 1.06 – 2.26 µg Zr/L) of respective measurement series. Method blanks from day 9 exhibit elevated Zr concentrations. This is maybe due to a contamination. However, these amounts of Zr (0.006 – 0.054 mg Zr/L) were far below concentrations in actual samples (< 0.2 %).
Test samples were diluted (dilution factor 100) so that the respective Zr concentrations would be in the calibrated range of the ICP-OES instrument. Constant zirconium concentrations as defined by the study guideline OECD 105 and the Regulation 440/2008/EC A.6 were measured from day 8 until day 9.

Results of preliminary tests

To estimate the water solubility preliminary tests (non-GLP) were performed. Therefore, a specific amount of test item was weighed into a vessel and 500 mL of argon-purged ultrapure water were added. After 24 h of stirring a sample was taken, filtered (0.2 µm, polyethersulfon membrane, DIA Nielsen, Dueren, Germany) and quantified by ICP-OES for its amount of zirconium.

A first preliminary test was performed with 20 g zirconium propionate/L ultrapure water. The concentration of dissolved zirconium was 50 mg/L after 24h of stirring. This corresponds to ~ 213 mg zirconium propionate/L (zirconium content 23.5%). No pH was measured at test start and after 24h of testing.

An additional preliminary test was performed with a loading of 0.101 g zirconium propionate/L. The zirconium concentration was quantified after 24h of stirring to be ~ 50 µg/L which corresponds to ~ 0.22 mg zirconium propionate/L. In this test flask from the second test the pH was measured to be 4.8 after adding the test item and 4.5 after 24 h.

The pH of an additional prepared solution with 1 g zirconium propionate/L (non-GLP) was determined to be 4.2 after 4 h.

The different results on solubility of zirconium propionate in water might be due to a slightly different pH value at saturation (4.5 to 4.2). A more likely explanation is that the higher the loadings the faster the solubility equilibrium is reached. Since the zirconium concentrations were measured after 24h only of each preliminary testing and with extremely different concentrations it is assumed that the reaction rate is extremely dependent on the loading.

However, after consultation with the monitor it was decided to use at least the loading of the first preliminary test for the water solubility main study to make sure, that solubility equilibrium will be reached

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

sample	measured concentration * dilution [mg Zr/L]	calculated level after addition [mg Zr/L]	average recovery [mg Zr/L] / [%]
vessel 1 sample a after 2 days dilution factor 100	38.96	52.37	48.86 / 93.3
vessel 1 sample b after 2 days dilution factor 100	39.73	52.98	50.74 / 95.8
vessel 2 sample a after 2 days dilution factor 100	52.70	63.36	61.09 / 96.4
vessel 2 sample b after 2 days dilution factor 100	52.89	63.51	61.00 / 96.1

 

Method validation summary

validation parameter	results	comment
selectivity	similar data with three different zirconium wavelengths for ICP-OES method	no interferences due to test media observed
linearity	applied calibration functions were linear	correlation coefficient at least 0.999442
limits of detection (LOD)	0.354– 0.755 µg Zr/L
limits of quantification (LOQ)	1.06 – 2.26 µg Zr/L
method blanks	conc. from days 1, 2, 3, 8 at least below LOQs of respective measurement series quantification (LOQ =1.06 – 2.26 µg Zr/L). Method blanks from day 9 elevated Zr concentrations (0.006 – 0.054 mg Zr/L) but far below conc. in actual samples (< 0.2 %)
accuracy and precision	mean recovery for Merck Zr standard (500 µg Zr /L): 102 ± 1 % (n = 3)	for concentration range of diluted samples
accuracy and precision	mean recovery for Merck Zr standard (250 µg Zr /L): 100 % (n = 1)	for concentration range of diluted samples
accuracy and precision	mean recovery for Merck Zr standard (100 µg Zr /L): 97.8 ± 1.7 % (n = 5)	for lower concentration range
accuracy and precision	mean recovery for Merck Zr standard (75 µg Zr /L): 101 % (n = 1)	For low concentration range
trueness	recovery from fortification of samples: 93.3 – 96.4 %
repeatability	mean recovery for Merck Zr standard (500 µg Zr /L): 102 ± 1 % (n = 3)	for concentration range of diluted samples
repeatability	mean recovery for Merck Zr standard (100 µg Zr /L): 97.8 ± 1.7 % (n = 5)	for lower concentration range

Constant zirconium concentrations were measured from day 8 until day 9, i.e. zirconium concentrations varied were less than 15 % between sampling points and no increase of the water solubility was observed. Thus, the validity criteria as foreseen in OECD 105 and Regulation 440/2008/EC A.6 were fulfilled.

The mean dissolved zirconium concentrations of solutions sampled from day 1 until day 3 were calculated.

Mean dissolved Zr concentrations day 8 – day 9:

Vessel 1: 49.9 ± 1.1 mg Zr/L

Vessel 2: 66.2 ± 0.83 g Zr/L

The amount of zirconium propionate dissolved was calculated based on the metal content of the test substance as follows:

 = mean of measured Zr concentration * 100 % / 23.5 % [Zr content of test item]

mean calculated zirconium propionate dissolved day 8 – day 9:

Vessel 1: 212.3 ± 4.7 mg/L

Vessel 2: 281.7 ± 3.4 mg/L

Conclusion

Under the conditions of this test (under exclusion of CO2 and O2, under inert argon gas; flask method; loadings of and 20.0018 and 20.0024 g/L in vessel 1 and 2, respectively), a solubility equilibrium was reached from day 8 until day 9 of testing. The mean amount of dissolved Zr from day 8 until day 9 at 20.0 ± 1.0 °C is 58.0 ± 8.8 mg/L (determined as dissolved Zr, separated by filtration from undissolved test item). This corresponds to a calculated water solubility of zirconium propionate of 246.89 ± 37.4 mg/L, calculated based on a zirconium content of 23.5 %. Solution pH in method blanks ranged from 5.5 to 6.2, whereas the pH in test item containing vessels were 4.1 – 4.2.

Conclusions:

Interpretation of results (migrated information): moderately soluble (100-1000 mg/L)
The test item zirconium propionate has a water solubility of 246.8 ± 37.4 mg/L at 20.0 ± 1.0 °C and pH 4.1 – 4.2.

Description of key information

Zirconium propionate has a water solubility of 246.8 ± 37.4 mg/L at 20.0 ± 1.0 °C and pH 4.1 – 4.2.

Key value for chemical safety assessment

Water solubility:

246.9 mg/L

at the temperature of:

20 °C