2-ethylhexanoic acid, copper salt

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018-05-30 to 2018-06-07

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

1995

Deviations:

yes

Remarks:

Two vessels were set up in a parallel design, each vessel was sampled several times instead of sampling one vessel at every point in time/ exclusion of O2 and CO2, under inert gas (argon)

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

2008

Deviations:

yes

Remarks:

Two vessels were set up in a parallel design, each vessel was sampled several times instead of sampling one vessel at every point in time/ exclusion of O2 and CO2, under inert gas (argon)

GLP compliance:

yes (incl. QA statement)

Remarks:

signed, 2016-05-31

Type of method:

flask method

Specific details on test material used for the study:

Appearance: Green powder
Storage conditions: Keep container tightly closed, in a dry place at room temperature.

Water solubility:

52.5 mg/L

Conc. based on:

element (dissolved fraction)

Remarks:

Cu

Loading of aqueous phase:

2 other: test item/L

Incubation duration:

>= 1 - <= 3 d

Temp.:

19.1 °C

pH:

>= 4.6 - <= 4.7

Remarks on result:

other: S.D.: ± 0.6 mg Cu/L

Water solubility:

340 mg/L

Conc. based on:

test mat. (dissolved fraction)

Loading of aqueous phase:

2 g/L

Incubation duration:

>= 1 - <= 3 d

Temp.:

19.1 °C

pH:

>= 4.6 - <= 4.7

Remarks on result:

other: S.D.: ± 4 mg/L

Remarks:

calculated based on a mean dissolved copper concentrations of 52.5 ± 0.6 mg/L and a copper amount of 15.42 % in the test item.

Details on results:

- The mean temperature was 19.1 ± 0.3 °C
- No oxygen was detectable
- The pH of test item solutions remained between 4.6 – 4.7, whereas the pH of the method blanks ranged between 6.4 – 7.3
- The turbidity in samples from the test was always < 1 NTU indicating that filtered solutions did not contain any undissolved material
- Validation: recovery was in the range of 100 ± 15 % of the respective certified value or the nominal/calculated values.

ICP-OES analysis with corresponding LOD/LOQ, correlation coefficient and sum of quality assurance samples and recovery

Calibration [µg/L] – lowest and highest calibration point	Chosen wavelength [nm]	LOD [µg/L]	LOQ [µg/L]	Correlation coefficient	Sum of quality assurance samples	Recovery of quality assurance samples [%]
June 06, 2018; measurement of test samples and method blanks (1d, 2d)
2.5 – 1000 (total of 13 calibration points, 12 used + blank)	219.227	1.46	4.37	0.999941	32	87.5
June 07, 2018; measurement of test samples and method blanks (3d)
1.0 – 1000 (total of 13 calibration points, 13 used + blank)	219.227	2.36	7.07	0.999980	16	100

 

Recovery/validation data copper of measurement series

Element Cu	Recovery [%]	SD [%]	n (total)	n (valid)
June 06, 2018
TMDA-70.2 (dilution factor 2), nominal value Cu: 406 µg/L – diluted 203 µg/L	102	13	6	5
Quality control standard (Roth) 5 µg/L	106	16	6	5
Quality control standard (Roth) 100 µg/L	105	1	6	6
Quality control standard (Roth) 750 µg/L	105	1	6	6
Recalibration standard 50 µg/L	98.1	1.2	6	4
June 07, 2018
TMDA-70.2 (dilution factor 2), nominal value Cu: 406 µg/L – diluted 203 µg/L	103	1	3	3
Quality control standard (Roth) 5 µg/L	97.3	4.4	3	3
Quality control standard (Roth) 100 µg/L	102	1	3	3
Quality control standard (Roth) 750 µg/L	102	1	3	3
Recalibration standard 50 µg/L	99.2	1	3	3

 

Selected samples were fortified with a known amount of copper (by standard addition of commercial standard) to determine the standard recoveries of this element.

Fortification of measurement series

Sample	Element	Measured concentration [µg/L]	Calculated level after addition [µg/L]	Recovery [µg/L] / [%]
June 06, 2018
Vessel 1 sample a 1d (dilution 100-fold) – 1 mL sample 4 mL 100 µg/L standard	Cu	526	185	180 / 96.9
Vessel 1 sample a 2d (dilution 100-fold) – 1 mL sample 4 mL 250 µg/L standard	Cu	524	305	320 / 105
June 07, 2018
Vessel 1 sample a 3d (dilution 100-fold) – 1 mL sample 4 mL 100 µg/L standard	Cu	399	160	164 / 103

 

Calculation of water solubility according to a copper content of 15.42 % in test item.

	Cu conc. [mg/L]	Mean Cu conc. [mg/L]	SD [mg/L]	Mean Cu both vessels [mg/L]	SD [mg/L]	Cu in test item [%]	Calculated amount of test item dissolved on basis of Cu [mg/L]	Mean dissolved test item [mg/L]	SD [mg/L]	Mean both vessels [mg/L]	SD [mg/L]
vessel 1 day 1 sample a	52.6	52.6	0.4	52.5	0.6	15.42	341	341	3	340	4
vessel 1 day 1 sample b	52.1						338
vessel 1 day 2 sample a	52.4						340
vessel 1 day 2 sample b	52.7						342
vessel 1 day 3 sample a	39.9^$						^$
vessel 1 day 3 sample b	53.2						345
vessel 2 day 1 sample a	51.9	52.4	0.7				337	340	4
vessel 2 day 1 sample b	51.3						333
vessel 2 day 2 sample a	53.0						344
vessel 2 day 2 sample b	52.9						343
vessel 2 day 3 sample a	52.8						343
vessel 2 day 3 sample b	52.5						341

^$  Outlier according to Shapiro Wilks and Grubbs test, not used for calculations

The water solubility of 2-ethylhexanoic acid, copper salt is based on mean dissolved copper concentrations of sampling days 1, 2, 3 and a copper amount of 15.42 % in the test item. The amount of dissolved 2-ethylhexanoic acid, copper salt was calculated as follows:

 

Mean copper concentrations analysed:

Vessel 1:       52.6 ± 0.4 mg/L

Vessel 2:       52.4 ± 0.7 mg/L

Mean:            52.5 ± 0.6 mg/L

 

Mean copper concentration x 100 % / 15.42 %:

Vessel 1:       341 ± 3 mg/L

Vessel 2:       340 ± 4 mg/L

Mean:            340 ± 4 mg/L 

Conclusions:

Under the conditions of this test (under exclusion of CO2 and O2, under inert gas; flask method; loadings of 2 g test item/L ultrapure water) solubility equilibrium was observed during testing on three consecutive days (variations between subsequent sampling points were less than 15 % and no increasing copper values were observed). The analysed dissolved copper concentration at 19.1 ± 0.3 °C is 52.5 ± 0.6 mg/L (determined as dissolved copper, separated by filtration < 0.2 µm from undissolved test item). This corresponds to a water solubility of 2-ethylhexanoic acid, copper salt of 340 ± 4 mg/L, calculated on a copper content of 15.42 %.
The pH of test item solutions remained between 4.6 – 4.7, whereas the pH of the method blanks ranged between 6.4 – 7.3.

Description of key information

2-Ethylhexanoic acid, copper salt has a water solubility of 340 ± 4 mg/L at 19.1  ± 0.3 °C.

Key value for chemical safety assessment

Water solubility:

340 mg/L

at the temperature of:

19.1 °C

Additional information

Under the conditions of this test (under exclusion of CO₂and O₂, under inert gas; flask method; loadings of 2 g test item/L ultrapure water solubility) equilibrium was observed during testing on three consecutive days (variations between subsequent sampling points were less than 15 % and no increasing copper values were observed). The analysed dissolved copper concentration at 19.1 ± 0.3 °C is 52.5 ± 0.6 mg/L (determined as dissolved copper, separated by filtration < 0.2 µm from undissolved test item). This corresponds to a water solubility of 2-ethylhexanoic acid, copper salt of 340 ± 4 mg/L, calculated on a copper content of 15.42 %.

The pH of test item solutions remained between 4.6 – 4.7, whereas the pH of the method blanks ranged between 6.4 – 7.3.