Fatty acids, C8-10, zinc salts

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:

2012-04-23 to 2012-12-06

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:

for details see field "details on methods"

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

2008

Deviations:

yes

Remarks:

for details see field "details on methods"

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2011-02-07

Type of method:

flask method

Specific details on test material used for the study:

- Stability: stable at normal ambient temperature and pressure

Water solubility:

338 mg/L

Conc. based on:

test mat.

Loading of aqueous phase:

1.5 g/L

Incubation duration:

>= 41 - <= 43 d

Temp.:

20 °C

pH:

>= 6 - <= 6.6

Remarks on result:

other: Estimated water solubility value calculated based on dissolved zinc and the zinc content of 18 %

Water solubility:

60.83 mg/L

Conc. based on:

element

Remarks:

Zn

Loading of aqueous phase:

1.5 other: g test item /L

Incubation duration:

>= 41 - <= 43 d

Temp.:

20 °C

pH:

>= 6 - <= 6.6

Details on results:

Under the conditions of this test (flask method; loadings of 1.5 g/L in vessel A and B, respectively), a solubility equilibrium was reached after 41 days. The mean amount of dissolved Zn from day 41 until day 43 at 20.0 ± 1.0 °C was 60.83 ± 3.53 mg Zn/L (determined as dissolved Zn, separated by filtration from undissolved test item). This corresponds to an estimated water solubility of dissolved fatty acids, C8-C10, zinc salts of 338.0 ± 19.6 mg/L, calculated based on a zinc content of 18 %. The pH measured in both test vessels remained relatively constant from 6.0 – 6.6. In both method blanks the pH ranged from 6.4 to 6.6, except after 14 and 28 days (5.7 – 5.9).

Observations

During the study, undissolved test material was observed in the medium, especially on the surface. Furthermore, test material was adsorbed to the flask wall. After filtration, the solution was clear. In order to verify this, turbidity was measured in filtered samples (see Table 3 and Table 4). The turbidity of blank and test solutions appears to be similar (see below).

Temperature

The study was performed in a thermostatically controlled temperature precise incubation cabinet (Binder, Tuttlingen, Germany). Besides the constant display of 20.0 °C, the temperature inside the cabinet was measured by a reference thermometer and remained at 20.0 °C (reading accuracy of 0.3 °C) at every sampling point.

Solution pH

The pH measured in both test vessels remained relatively constant from 6.0 – 6.6. In both method blanks the pH ranged from 6.4 to 6.6, except after 14 and 28 days (5.7 – 5.9). The temperature measurements of the pH meter varied marginally from those of the reference thermometer and were not always at 20.0 ± 1.0 °C. The pH meter was calibrated for pH measurements every working week and furthermore verified every working day; however, this calibration was not performed for the temperature measurement since a reference thermometer was used during the test. All measured pH values are listed in Table 1and Table 2.

Table 1: Solution pH of solutions containing the test item

test day [d]	sample vessel	temperature of pH measurement [°C]	pH	sample vessel	temperature of pH measurement [°C]	pH
2	A	20.6	6.2	B	21.3	6.4
3	A	20.7	6.4	B	21.4	6.5
4	A	20.6	6.2	B	21.3	6.4
14	A	20.6	6.5	B	21.0	6.6
28	A	20.6	6.0	B	21.5	6.1
41	A	20.3	6.4	B	20.1	6.4
42	A	21.2	6.3	B	20.3	6.3
43	A	20.5	6.4	B	20.4	6.3

 

Table 2: Solution pH of method blanks 

test day [d]	blank vessel	temperature of pH measurement [°C]	pH	blank vessel	temperature of pH measurement [°C]	pH
2	A	19.9	6.5	B	20.1	6.5
3	A	20.0	6.6	B	20.3	6.4
4	A	19.7	6.6	B	20.2	6.6
14	A	20.0	5.9	B	20.2	5.8
28	A	19.5	5.7	B	19.8	6.0
41	A	19.8	6.6	B	19.9	6.5
42	A	20.5	6.6	B	20.4	6.5
43	A	20.7	6.6	B	20.6	6.5

Turbidity

The turbidity was measured after filtering to verify that only dissolved zinc concentrations would get measured. The turbidity was always <<1 NTU, indicating that there was not any undissolved material left and micelles did not form after the filtration step. Turbidity data are compiled in Table 3 and Table 4.

Table 3: Turbidity of samples

test day [d]	turbidity of sample vessel A [NTU]	turbidity of sample vessel B [NTU]
2	0.16	0.12
3	0.12	0.09
4	0.18	0.16
14	0.04	0.05
28	0.08	0.16
41	0.09	0.08
42	0.08	0.10
43	0.08	0.10

 

Table 4: Turbidity of blanks 

test day [d]	turbidity of blank vessel 1 [NTU]	turbidity of blank vessel 2 [NTU]
2	0.04	0.07
3	0.05	0.02
4	0.06	0.09
14	0.04	0.05
28	0.08	0.07
41	0.03	0.04
42	0.02	0.05
43	0.03	0.04

Dissolved zinc concentrations

Dissolved Zn concentrations in most method blanks sampled at each time point were below the limits of detection (< 14 – < 41 µg/L) of the respective measurement series. All test samples were diluted (dilution factor 100), so that the respective zinc concentrations would be in the calibrated range of the ICP-OES instrument. The variation of zinc concentrations between subsequent sampling points is listed in Table 5 (in percent). Constant zinc concentrations as defined by the study guideline OECD 105 and the Regulation 440/2008/EC A.6 were measured from day 41 until day 43. 

Table 5: Measured Zn concentrations in test samples (internal calculations were performed with more digits, values were rounded)

test day [d]	Zn conc. of samples vessel A [mg/L]	mean Zn conc. ± SD vessel A [mg/L]	Zn conc. of samples vessel B [mg/L]	mean Zn conc. ± SD vessel B [mg/L]	mean Zn mean conc. ± SD [mg/L]	variation between samplings [%]
2	25.77	25.94 ± 0.23	30.66	30.55 ± 0.16	28.24 ± 2.67	-
	26.10		30.44
3	34.11	34.02 ± 0.13	38.82	38.97 ± 0.21	36.49 ± 2.86	29.2
	33.93		39.11
4	41.03	41.21 ± 0.25	48.09	48.15 ± 0.08	44.68 ± 4.01	22.4
	41.39		48.2
14	46.61	46.46 ± 0.22	58.29	58.49 ± 0.28	52.47 ± 6.95	17.4
	46.30		58.69
28	51.26	51.40 ± 0.19	62.76	62.74 ± 0.04	57.07 ± 6.55	8.8
	51.53		62.71
41	55.23	55.24 ± 0.01	61.75	61.66 ± 0.13	58.45 ± 3.71	2.4
	55.24		61.56
42	58.06	57.99 ± 0.11	62.73	62.86 ± 0.18	60.42 ± 2.81	3.4
	57.91		62.98
43	61.38	61.55 ± 0.23	65.82	65.72 ± 0.14	63.63 ± 2.42	5.3
	61.71		65.62

Table 6: Measured zinc concentrations in method blanks

test day [d]	Zn conc. blank A [µg/L]	Zn conc. blank B [µg/L]	LOD [µg/L]	LOQ [µg/L]
2	< LOD	< LOD	37	122
	< LOD	< LOD
3	< LOD	< LOD	37	122
	< LOD	< LOD
4	< LOD	< LOD	37	122
	< LOD	< LOD
14	< LOQ (3.36)	6.1	1.49	4.96
	< LOQ (3.26)	6.1
28	< LOD	< LOD	41	138
	< LOD	< LOD
41	< LOD	< LOD	22	72
	< LOD	< LOD
42	< LOD	< LOD	22	72
	< LOD	< LOD
43	< LOD	< LOD	14	46
	< LOD	< LOD

Conclusions:

Interpretation of results: moderately soluble (100-1000 mg/L)
Under the conditions of this test (flask method; loadings of 1.5000 g/L in vessel A and B, respectively), a solubility equilibrium was reached after 41 days. The mean amount of dissolved Zn from day 41 until day 43 at 20.0 ± 1.0 °C was 60.83 ± 3.53 mg Zn/L (determined as dissolved Zn, separated by filtration from undissolved test item). This corresponds to an estimated water solubility of dissolved fatty acids, C8-C10, zinc salts of 338.0 ± 19.6 mg/L, calculated based on a zinc content of 18 %. The pH measured in both test vessels remained relatively constant from 6.0 – 6.6. In both method blanks the pH ranged from 6.4 to 6.6, except after 14 and 28 days (5.7 – 5.9).

Reference 2

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2009-08-07 to 2009-09-07

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2007-03-21

Type of method:

flask method

Specific details on test material used for the study:

- Storage condition of test material: Keep the original container tightly closed and in a cool, well ventilated area.

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

15.74 mg/L

Element analysed:

Zn

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

Temp.: 21.5 °C, pH 7

Remarks on result:

other: Media TM2

Remarks:

average of three samples

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

15.95 mg/L

Element analysed:

Zn

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

Temp.: 21.5 °C, pH 8

Remarks on result:

other: Media TM1

Remarks:

average of three samples

Details on results:

Due to the nearly complete transformation / dissolution of Ligastab ZN 108 in media at pH below 8, the full transformation/ dissolution tests over 7 days and prolongation to 28 days with different loadings (1, 10 and 100 mg/L) were not needed for a further characterization of the T/D behavior. The data from this screening test combined with the pH optimization test yielded sufficient information to quantify the T/D behavior.

To quantify the transformed/dissolved amount of Ligastab ZN 108, the mean Zn concentration was determined in test media with different pH values ranging from 5.5 to 8.5 after agitating for 24 hours. The highest amount of measured zinc was 15.74 mg/L in the first test run and 15.95 mg/L in the repetition. Considering the composition of the test item as described in the CoA, 16.92 mg Zn were expected to be in 100 mg of Ligastab ZN 108.

The maximum dissolution of the test substance after 24 h in test run 1 and 2 was calculated as follows:
Test run 1:
15.74 ± 0.1 mg/L (max. Zn conc.) * 100.4 mg (loading in 1 L) / 16.92 mg (Zn in 100 mg) = 93.4 ± 0.6 mg/L => 93.0 % of the zinc loading was dissolved.
Test run 2:
15.95 ± 0.2 mg/L (max. Zn conc.) * 100.1 mg (loading in 1 L) / 16.92 mg (Zn in 100 mg) = 94.4 ± 1.2 mg/L=> 94.3 % of the zinc loading was dissolved.

Conclusions:

The 24-h transformation/dissolution of Fatty acids, C8-10, zinc salts with a zinc content of 16.92 % results at a loading of 100 mg/L and at pH 7 and pH 8 in dissolved zinc levels of 15.74 and 15.95 mg/L, respectively.

Description of key information

Based on measured maximum zinc concentrations, the water solubility of Fatty acids, C8-10, zinc salts is 338.0 mg/L at pH 6 and at 20 °C.

Key value for chemical safety assessment

Water solubility:

338 mg/L

at the temperature of:

20 °C

Additional information

Water solubility (Klawonn, 2013):

Under the conditions of this test (flask method; loadings of 1.5 g/L in vessel A and B, respectively), a solubility equilibrium was reached after 41 days. The mean amount of dissolved Zn from day 41 until day 43 at 20.0 ± 1.0 °C was 60.83 ± 3.53 mg Zn/L (determined as dissolved Zn, separated by filtration from undissolved test item). This corresponds to an estimated water solubility of dissolved fatty acids, C8-C10, zinc salts of 338.0 ± 19.6 mg/L, calculated based on a zinc content of 18 %. The pH measured in both test vessels remained relatively constant from 6.0 – 6.6. In both method blanks the pH ranged from 6.4 to 6.6, except after 14 and 28 days (5.7 – 5.9).

Transformation/dissolution (Rüdel, 2010):

The 24-h transformation/dissolution of Fatty acids, C8-10, zinc salts with a zinc content of 16.92 % results at a loading of 100 mg/L and at pH 7 and pH 8 in dissolved zinc levels of 15.74 and 15.95 mg/L, respectively.