Naphthenic acids, copper salts

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018-08-10 to 2018-09-20

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:

Three 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:

Three 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:

2019-07-15

Type of method:

flask method

Specific details on test material used for the study:

Appearance: Green, viscous paste
Storage conditions: -15 °C to 40 °C, in sealed container

Key result

Water solubility:

70.9 mg/L

Conc. based on:

test mat. (dissolved fraction)

Loading of aqueous phase:

300 mg/L

Incubation duration:

37 d

Temp.:

20 °C

pH:

>= 5.68 - <= 6.13

Remarks on result:

other: S.D: ± 6.0 mg/L

Remarks:

Calculated on a mean dissolved copper concentration of 8.5 ± 0.7 mg/L and a copper content of 12.0 %.

Water solubility:

8.5 mg/L

Conc. based on:

element (dissolved fraction)

Remarks:

Cu

Loading of aqueous phase:

300 other: mg test item/ L

Incubation duration:

37 d

Temp.:

20 °C

pH:

>= 5.68 - <= 6.13

Remarks on result:

other: S.D: ± 0.7 mg/L

Details on results:

- Observations: A small amount of undissolved material was observed at the surface of the test solutions but mostly adhered at the sample boat. Sample boats were transferred inside the test vessels prior to start. For the method blank vessels, blank sample boats were added to the ultrapure water.
- Mean temperature: 20.1 ± 0.2 °C.
- Oxygen: no oxygen was detectable.
- pH: test item solutions: 5.3 - 6.6; method blanks: 8.5 (day 1), 7.2 – 7.9 (day 2 - 36), 6.0 and 6.5 (day 37)
- Turbidity: always < 1 NTU indicating that filtered solutions did not contain any undissolved material
- Analytical measurements:
Subtraction of method blanks is not needed. The Cu concentrations in method blanks were below LOD / LOQ or far below concentrations in actual samples.
Increase of concentrations from day 36 to day 37 were less than 15 % (validity criteria as foreseen in OECD 105 and Regulation 440/2008/EC A.6 were fulfilled).
Copper concentrations increased during the test from day 1 and 37 and even slightly from day 34 to day 35. Thus, an equilibrium could not be observed. However, further sampling was not possible.

ICP-MS measurement series on with corresponding LOD/LOQ, correlation coefficient and sum of quality assurance samples and recovery.

Chosen isotope and gas mode	LOD [µg Cu/L]	LOQ [µg Cu/L]	Correlation coefficient	Sum of quality assurance samples	Recovery of quality assurance samples [%]
August 16, 2018; measurement of test samples and method blanks (days 1, 2, 3d)
^63Cu in helium mode	0.007	0.020	1.0000	26	100
August 31, 2018; measurement of test samples and method blanks (days 15, 16, 17d)
^63Cu in high helium mode	0.001	0.003	1.0000	19	100
September 13, 2018; measurement of test samples and method blanks (days 29, 30, 31)
^63Cu in high helium mode	0.002	0.007	0.9997	31	100
September 20, 2018; measurement of test samples and method blanks (days 36, 37)
^63Cu in high helium mode	0.005	0.014	0.9997	22	100

 

Recovery/validation data copper of measurement

Element Cu	Recovery [%]	SD [%]	n (total)	n (valid)
August 16, 2018
Quality control standard (Roth) 40 µg/L	96.7	2.5	6	6
Recalibration standard 100 µg/L	98.5	1.8	6	6
TMDA-70.2 (dilution factor 2), nominal value Cu: 406 µg/L – diluted 203 µg/L	100	2.1	6	6
Quality control standard (Roth) 400 µg/L	97.0	2.3	6	6
August 31, 2018
Quality control standard (Roth) 40 µg/L	101	2.1	4	4
Recalibration standard 100 µg/L	102	1.0	4	4
TMDA-70.2 (dilution factor 2), nominal value Cu: 406 µg/L – diluted 203 µg/L	106	0.9	4	4
Quality control standard (Roth) 400 µg/L	101	0.6	4	4
September 13, 2018
Quality control standard (Roth) 40 µg/L	102	1.4	7	7
Recalibration standard 100 µg/L	101	0.9	7	7
TMDA-70.2 (dilution factor 2), nominal value Cu: 406 µg/L – diluted 203 µg/L	105	0.8	7	7
Quality control standard (Roth) 400 µg/L	101	1.2	7	7
September 20, 2018
Quality control standard (Roth) 40 µg/L	104	1.7	5	5
Recalibration standard 100 µg/L	102	0.5	5	5
TMDA-70.2 (dilution factor 2), nominal value Cu: 406 µg/L – diluted 203 µg/L	108	1.3	5	5
Quality control standard (Roth) 400 µg/L	104	1.1	5	5

 

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

Fortification of measurement series

Sample	Element	Measured concentra-tion [µg/L]	Calculated level after addition [µg/L]	Recovery [µg/L] / [%]
August 16, 2018
Vessel 1 sample a 1d (dilution 20-fold) – 1 mL sample 4 mL 60 µg/L standard	Cu	14.3	50.9	49.6 / 97.5
Vessel 2 sample b 3d (dilution 10-fold) – 1 mL sample 4 mL 100 µg/L standard	Cu	78.0	95.6	93.7 / 98.0
August 31, 2018
Vessel 1 sample a 15d (dilution 10-fold) – 1 mL sample 4 mL 300 µg/L standard	Cu	277	285	286 / 100
Vessel 2 sample a 16d (dilution 10-fold) – 1 mL sample 4 mL 400 µg/L standard	Cu	310	382	382 / 99.9
Vessel 3 sample a 17d (dilution 10-fold) – 1 mL sample 4 mL 500 µg/L standard	Cu	402	480	480 / 100
September 13, 2018
Vessel 1 sample a 29d (dilution 50-fold) – 1 mL sample 4 mL 200 µg/L standard	Cu	135	187	187 / 99.7
Vessel 2 sample a 30d (dilution 50-fold) – 1 mL sample 4 mL 300 µg/L standard	Cu	119	264	255 / 96.6
Vessel 3 sample a 31d (dilution 50-fold) – 1 mL sample 4 mL 300 µg/L standard	Cu	126	265	264 / 99.5
September 20, 2018
Vessel 3 sample a 36d (dilution 50-fold) – 1 mL sample 4 mL 200 µg/L standard	Cu	147	189	197 / 104
Vessel 2 sample a 37d (dilution 50-fold) – 1 mL sample 4 mL 300 µg/L standard	Cu	176	275	281 / 102

Calculation of water solubility according to copper content of 12%.

Sample	Cu conc. [mg/L]	mean Cu all samples [mg/L]	SD [mg/L]	Cu in test item [%]	Calculated amount of test item dissolved on basis of Cu (100% Purity) [mg/L]	Mean dissolved test item [mg/L]	SD [mg/L]	Mean all samples [mg/L]	SD [mg/L]
Vessel 1a day 37	8.79	8.51	0.71	12.0	73.3	70.9	5.9	70.9	5.9
Vessel 1b day 37	8.76				73.0
Vessel 2a day 37	9.12				76.0
Vessel 2b day 37	9.17				76.4
Vessel 3a day 37	7.56				63.0
Vessel 3b day 37	7.67				64.0

Conclusions:

Under the conditions of this test (under exclusion of CO2 and O2, under inert gas; flask method; loadings of ~300 mg/L test substance in three replicates), a solubility equilibrium was not reached after day 37 of testing. The mean measured dissolved copper concentration (after filtration 0.2 µm) on day 37 at 20.0 ± 0.3 °C is 8.5 ± 0.7 mg/L.
This corresponds to a water solubility of dissolved copper naphthenate of 70.9 ± 6.0 mg/L, calculated on a copper content of 12.0 %.

Description of key information

Copper naphthenate has a water solubility of 70.9 ± 6.0 mg/L at 20 °C.

Key value for chemical safety assessment

Water solubility:

70.9 mg/L

at the temperature of:

20 °C

Additional information

Under the conditions of this test (under exclusion of CO2 and O2, under inert gas; flask method; loadings of ~300 mg/L test substance in three replicates), a solubility equilibrium was not reached after day 37 of testing. The mean measured dissolved copper concentration (after filtration 0.2 µm) on day 37 at 20.0 ± 0.3 °C is 8.5 ± 0.7 mg/L.

This corresponds to a water solubility of dissolved copper naphthenate of 70.9 ± 6.0 mg/L, calculated on a copper content of 12.0 %.