Zinc methacrylate

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

From 09 to 20 March 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: ISO ISO 17025

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

other: OECD Test Guideline No 29 (2001)

Deviations:

not specified

GLP compliance:

no

Type of method:

other: an inductively coupled plasma and masss pectrometry (ICP/MS)

Key result

Water solubility:

ca. 100 mg/L

Remarks on result:

completely miscible

Details on results:

The substance zinc dimethacrylate is demonstrated to readily dissolve into test medium at pH 6 and 8 within 12 h under the test conditions described in this report (100 mg/L loading rate, 20°C, 200rpm agitation). The transformation of zinc in aquatic environment is well-known to be dependent of numbers of factors like pH and redox potential. Under the conditions of this study, about 20% of the dissolved zinc precipitated as the sparingly soluble zinc hydroxide Zn(OH)2 at pH 8, causing also a pH shift from pH 8 to pH 7. The overall results may be relevant for consideration under the
REACh and CLP requirements.

The raw data observed and measured are presented in Annexes 1 to 5.

The temperature of the test solutions fluctuates between 20.3 and 20.5°C and corresponded to the required test conditions of 20 – 23°C.

The pH measured in the test media and in the blank and test item vessels at pH 6 varied from 6.00 to 6.02 and were within the specifications of ± 0.2. The pH measured in the test media and in the blank vessels at pH 8 varied from 7.99 to 8.01 and were within the specifications of ± 0.2. The pH in the test item vessels at pH 8 however shifted to pH 7 due to a precipitation reaction of zinc. The pH (pH 8) couldn’t be stabilised with air buffering. The dissolved oxygen concentration measured in the test media, blank and test item vessels at pH 6 and pH 8 varied from 8.54 to 8.60. These values are higher than the target value of ± 6 mg O2/L at 22°C which means more than 70% of the saturation concentration in contact with the air. The reporting limit (RL) for dissolved zinc (Zn) in the test media at pH 6 and 8 are presented in Annex 7. The raw data of the total organic carbon content (TOC) and of the dissolved zinc (Zn) concentration in the test media, measured by the Test Site WLN with a TOC analyzer and a ICP–MS respectively, are presented in Annex 9. The total organic carbon content (TOC) of the (modified) ISO 6341 aqueous media were below reporting limit (1.0 mg/L C) for both media at pH 6 and pH 8.

Both results were within the requirement of <2 mg/L C (Annex 9).

The blank values of zinc (Zn) in the test medium at pH 6 and 8, and in the blank control vessels after 24-h incubation at test conditions were below the reporting limit of zinc (4 μg/L Zn). (Annex 1, 2 and 4)

The dissolved zinc (Zn) concentration in the blank corrected test vessels at pH 6 showed an average value of 27 mg/L Zn. This value was already achieved after a 12h exposure and is about 97% of the nominal concentration of zinc (27.8 mg/L Zn) from a 100 mg/L loading rate of zinc dimethacrylate. (Annex 3)

The dissolved zinc (Zn) concentration in the blank corrected test vessels at pH 8 showed an average value of 22 mg/L Zn. This value was already achieved after a 12h exposure and is about 79% of the nominal concentration of zinc (27.8 mg/L Zn) from a 100 mg/L loading rate of zinc dimethacrylate. There was clearly a precipitate of zinc hydroxide Zn(OH)2 observable which also explains the pH shift from pH 8 to pH 7. (Annex 5)

Conclusions:

The substance zinc methacrylate is demonstrated to readily dissolve into test medium at pH 6 and 8 within 12 h under the test conditions described in this report (100 mg/L loading rate, 20°C, 200rpm agitation). The transformation of zinc in aquatic environment is well-known to be dependent of numbers of factors like pH and redox potential. Under the study conditions, about 20% of the dissolved zinc precipitated as the sparingly soluble zinc hydroxide Zn(OH)2 at pH 8, causing also a pH shift from pH 8 to pH 7.

Executive summary:

This study was performed in order to obtain (more) information about the fate of Zinc dimethacrylate in water and to identify potential rapid dissolution of zinc according to the OECD Test Guideline No 29 (2001), the SOPs and the ISO ISO 17025 using the(ICP/MS). The pH measured in the test media and in the blank and test item vessels at pH 6 varied from 6.00 to 6.02 and were within the specifications of ± 0.2. The pH measured in the test media and in the blank vessels at pH 8 varied from 7.99 to 8.01 and were within the specifications of ± 0.2. The pH in the test item vessels at pH 8 however, shifted to pH 7 due to a precipitation reaction of zinc. The measured dissolved oxygen concentrations in the test medium, the blank controls and test vessels at pH 6 and pH 8 varied between 8.54 and 8.60 and were higher than the value of ± 6 mg O2/L which is considered as 70% of the saturation concentration in contact with the air. The dissolved zinc concentration in the test media (pH 6 and pH 8) and in the blank test vessels at both pH ranges, were below the reporting limit of zinc (4 μg/L Zn). The dissolved zinc (Zn) concentration in the blank corrected test vessels at pH 6 showed an average value of 27 mg/L Zn. This is about 97% of the nominal concentration of zinc (27.8 mg/L Zn) in the test item. The dissolved zinc (Zn) concentration in the blank corrected test vessels at pH 8 showed an average value of 22 mg/L Zn. This is about 79% of the nominal concentration of zinc in the test item. A precipitate of zinc hydroxide was clearly observable. These results suggest that zinc dimethacrylate dissociates easily in water at pH range 6 to 8 as zinc ions and as methacrylate ions. The substance zinc methacrylate is demonstrated to readily dissolve into test medium at pH 6 and 8 within 12 h under the test conditions described in this report (100 mg/L loading rate, 20°C, 200rpm agitation). The transformation of zinc in aquatic environment is well-known to be dependent of numbers of factors like pH and redox potential. Under the study conditions, about 20% of the dissolved zinc precipitated as the sparingly soluble zinc hydroxide Zn(OH)2 at pH 8, causing also a pH shift from pH 8 to pH 7 (Brouwers, 2012).

Reference 2

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 31 May to 18 June 2012

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

This study showed that the limit of solubility of ZDMA could not be reached because of the dependency of solubility on amount of the test item.

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Key result

Water solubility:

10.7 g/L

Conc. based on:

test mat. (dissolved fraction)

Loading of aqueous phase:

12.002 g/L

Temp.:

20 °C

pH:

6.5

Remarks on result:

other:

Details on results:

The solubility of zinc methacrylate in water was determined from the measured concentrations of dissolved Zinc in the filtrated test solutions. Equilibration time can be considered as approximately two days, as the values which were measured on the following consecutive days did not give significantly different values. Accuracy measurements via standard addition showed a correlation r² = 1, indicating that no matrix effects were present. All replicates showed poor correspondence, as dependency of solubility on amount of the
test item (nominal load) was perceived. The concentration of test item in water (based on measured dissolved Zinc concentrations) lay in the range 3.05 – 10.70 g/L for the nominal concentration range of the test item in water 3.5 – 12.0 g/L. 88 % of the test item was dissolved in water, calculated from the nominal concentration of the test item.

Measurements for Temperature Dependency of Water Solubility. The data which was acquired for temperature dependency of water solubility is presented in the following table:

Flask	Temperature in °C	Zn (diluted sample)in mg/L	Dilution factor	Zn Conc. (original sample)in mg/L	Difference to previous sample %	Concentration test item in g/L
1A	22	0.177	5000	885		3.19
2A	5	0.187	5000	935	5.7 %	3.37

As the difference between the measured concentrations of the two flasks was 3%/°C (5.7 %/17 °C), the main study was performed at 20 °C only.

Measurements during Equilibration

The data which was acquired during equilibration time (flask 1) is presented in the following table:

Day	Temperature in °C	pH*	Zn Concentration (diluted)in mg/L	Dilution factor	Zn Concentration (original)in mg/L	Difference to previous sample %	Factor Zn/test item	Concentration test item in mg/L
1	20.0	6	0.198	10000	1980	--	0.2777	7131
2	19.5	6	0.200	10000	2000	1.0	0.2777	7203
3	20.0	6	0.201	10000	2010	0.5	0.2777	7239
4	19.5	6	0.203	10000	2030	1.0	0.2777	7311
7	20.0	6.52	0.202	10000	2020	-0.5	0.2777	7275

*on days 1-4, pH was measured using pH paper, on day 7 pH was measured using a pH meter.

After the analysis of the sample of day 7, the plateau was considered as reached.

Measurements at Plateau:

The concentrations of Zn were determined from the measured values following the equation.

The following table gives the values which were measured at the plateau.

Flask	2	3	4	5	6
pH	6.54	6.59	6.55	6.54	6.53
Measured value (absorption)	0.10745	0.15585	0.14235	0.15801	0.18557
Recovery rate of QC sample in %	103.4	103.4	103.4	103.4	103.4
Concentration Zn in mg/L (diluted sample)	0.176	0.257	0.234	0.261	0.309
Dilution factor	5000	5000	10000	10000	10000
Concentration Zn in mg/L (original sample)	880	1285	2340	2610	3090
Factor (Zn/Test Item)	0.2777	0.2777	0.2777	0.2777	0.2777
Concentration test item in mg/L	3169	4628	8428	9400	11129

The content of ZnO ash in the test item (35.92 %) as presented by the sponsor was used to calculate the content of Zinc in zinc methacrylate (28.87 %). Temperature was measured with 20.0 °C. A standard deviation of 3.21 g/L was calculated, giving a relative standard deviation of 45 %, as dependency of solubility on amount of the test item (nominal load) was perceived in flasks 2 – 6.

Measurements used for Calculation of Solubility

Flask	2	3	4	5	6
Concentration test item in mg/L	3169	4628	8428	9400	11129
Conc. test item (nominal) in mg/L	3504	5004	9000	10510	12002
Dissolved part in %	90.45	92.49	93.64	89.44	92.72

Graph

No exact solubility of the test item in water could be stated, as dependency of solubility on amount of the test item (nominal load) was perceived in flasks 2 – 6:

The concentration of test item in water (based on measured Zn concentrations) lay in the range 3.05 – 10.70 g/L at 20 ± 0.5 °C = 3.05 – 10.70 * 10-3 kg/m3 (SI units) for the following nominal concentration range of the test item in water: 3.5 – 12.0 g/L. Approx. 88 % of the test item was dissolved in water, calculated from the nominal concentration of the test item, based on measured dissolved zinc concentrations.

Conclusions:

Equilibration time can be considered as approximately two days, as the values which were measured on the following consecutive days did not give significantly different values. All replicates showed poor correspondence, as dependency of solubility on amount of the test item (nominal load) was perceived. The concentration of test item in water (based on measured dissolved Zinc concentrations) lay in the range 3.05 – 10.70 g/L for the nominal concentration range of the test item in water 3.5 – 12.0 g/L. 88 % of the test item was dissolved in water, calculated from the nominal concentration of the test item.

Executive summary:

This study was performed according to OECD 105 and EU Method A.6 in order to determine the water solubility of Zinc methacrylate. In a preliminary study, solubility of the test item in water could be estimated as approx. 652 mg/L (from the nominal concentration of the test item in water 1000 mg/L). The flask method was used for the determination of the solubility of the test item in water. In the main study, amount of test item were weighed into each of six individual vessels, water was added, to prepare solutions with nominal concentration ranging from 3504 to 12002 mg/L. Then, vessels were shaken at 20.0 ± 0.5 °C for 24 hours up to 7 days. On the days 1, 2, 3, 4 and 7, vessel 1 was taken from the shaking apparatus and stored at 20.0 ± 0.5 °C for equilibration. Samples were taken, filtrated (0.45 μm) and analysed using AAS for Zinc as shaking of the test vessels was continued. Equilibration time can be considered as approximately two days, as the values which were measured on the following consecutive days did not give significantly different values. Accuracy measurements via standard addition showed a correlation r² = 1, indicating that no matrix effects were present. All replicates showed poor correspondence, as dependency of solubility on amount of the test item (nominal load) was perceived. The concentration of test item in water (based on measured dissolved Zinc concentrations) lay in the range 3.05 – 10.70 g/L for the nominal concentration range of the test item in water 3.5 – 12.0 g/L. 88 % of the test item was dissolved in water, calculated from the nominal concentration of the test item. This study was considered reliable with restriction. Indeed, this study was showed that the limit of solubility of ZDMA could not be reached because of the dependency of solubility on amount of the test item. Therefore, the water solubility of the substance was considered to be 10.7 g/L related to the nominal concentration of 12.002 g/L (Affolter, 2012).

Description of key information

The water solubility was determined according to OECD 105 and EU Method A.6 (Affolter, 2012).

Key value for chemical safety assessment

Water solubility:

10.7 g/L

at the temperature of:

20 °C

Additional information

The concentration of test item in water (based on measured dissolved Zinc concentrations) lay in the range 3.05 – 10.70 g/L for the nominal concentration range of the test item in water 3.5 – 12.0 g/L. 88 % of the test item was dissolved in water, calculated from the nominal concentration of the test item. This study was considered reliable with restriction. Indeed, this study was showed that the limit of solubility of ZDMA could not be reached because of the dependency of solubility on amount of the test item. Therefore, the water solubility of the substance was considered to be 10.7 g/L based on the nominal concentration of 12.002 g/L.