Dizinc orthosilicate

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

27 May 2016 to 11 Juy 2016

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

Qualifier:

according to guideline

Guideline:

other: EEC guideline SANCO/3029/99 rev. 4 dated 11/07/00: Working document “Guidance for generating and reporting methods of analysis in support of residue data requirements for Annex II (part A, Section 4) and Annex III (part A, Section 5)

GLP compliance:

yes (incl. QA statement)

Type of method:

other: Transformation / dissolution test

Specific details on test material used for the study:

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: None
- Final preparation of a solid: 1 mg of test item was added to the test medium

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

106.05 µg/L

Element analysed:

Zinc

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

test medium pH 6, room temperature

Remarks on result:

other: SD = 10.10 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

145.68 µg/L

Element analysed:

Zinc

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

test medium pH 6, room temperature

Remarks on result:

other: SD = 19.4 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

144.77 µg/L

Element analysed:

Zinc

Loading of aqueous phase:

1 mg/L

Incubation duration:

14 d

Test conditions:

test medium pH 6, room temperature

Remarks on result:

other: SD = 5.65 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

162.01 µg/L

Element analysed:

Zinc

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

Test medium pH 6, room temperature

Remarks on result:

other: SD = 18.17 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

28.02 µg/L

Element analysed:

Zinc

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

Test medium pH 8, room temperature

Remarks on result:

other: SD = 2.57 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

26.02 µg/L

Element analysed:

Zinc

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

Test medium pH 8, room temperature

Remarks on result:

other: SD = 1.30 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

20.31 µg/L

Element analysed:

Zinc

Loading of aqueous phase:

1 mg/L

Incubation duration:

14 d

Test conditions:

Test medium pH 8, room temperature

Remarks on result:

other: SD = 1.45 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

18.93 µg/L

Element analysed:

Zinc

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

Test medium pH 8, room temperature

Remarks on result:

other: SD = 0.56 µg/L

Details on results:

After 28 days, 162.01 and 18.93 µg/L of zinc had been released from the test item at pH 6 and pH 8, respectively. Considering an initial Zinc silicate load of 1 mg and a maximum possible zinc release of 597 µg/L (calculated from the test item composition) the test results indicate that zinc is released from the test item in greater amounts in test medium at pH 6. In test medium at pH 8 a slow decrease of zinc metal released during the test was observed (from 45.54 µg/L after 2 hours to 18.93 µg/L after 28 days). The decrease of zinc concentration in the test medium at pH8 during the test is probably due to the oxidizing process.

TABLE 1a Summary table: Zinc Silicate 28-day full test with a  loading of 1 mg/L at pH6

 

Full test 28 days at 1 mg/L pH 6 2926585-001		^64Zn (µg/L)	Full test 28 days at 1 mg/L pH 6 2926585-001		^64Zn (µg/L)
Test medium pH 6 T0 hour	Mean	n.d.	Test medium pH 6 T7 days	Mean	145.68
	S.D.	-		S.D.	19.40
	RSD%	-		RSD%	13.32
Test medium pH 6 T2 hours	Mean	73.91	Test medium pH 6 T14 days	Mean	144.77
	S.D.	9.66		S.D.	5.65
	RSD%	13.07		RSD%	3.82
Test medium pH 6 T6 hours	Mean	83.64	Test medium pH 6 T21 days	Mean	159.33
	S.D.	1.49		S.D.	12.13
	RSD%	1.78		RSD%	7.61
Test medium pH 6 T24 hours	Mean	106.05	Test medium pH 6 T28 days	Mean	162.01
	S.D.	10.10		S.D.	18.17
	RSD%	9.52		RSD%	11.22
Test medium pH 6 T4 days	Mean	134.74	-
	S.D.	17.41
	RSD%	12.92

n.d.: lower than the Limit of Detection (L.O.D. = 0.50 µg/L for Zn).

 The between-vessel variation was less than 20% recommended by OECD Series No. 29.

 

TABLE 1b Summary table: Zinc Silicate 28-day full test with a  loading of 1 mg/L at pH8

 

Full test 28 days at 1 mg/L pH 8 2926585-001		^64Zn (µg/L)	Full test 28 days at 1 mg/L pH 8 2926585-001		^64Zn (µg/L)
Test medium pH 8 T0 hour	Mean	n.d.	Test medium pH 8 T7 days	Mean	26.02
	S.D.	-		S.D.	1.30
	RSD%	-		RSD%	5.01
Test medium pH 8 T2 hours	Mean	45.54	Test medium pH 8 T14 days	Mean	20.31
	S.D.	6.63		S.D.	1.45
	RSD%	14.56		RSD%	7.16
Test medium pH 8 T6 hours	Mean	43.86	Test medium pH 8 T21 days	Mean	19.17
	S.D.	3.23		S.D.	1.59
	RSD%	7.37		RSD%	8.29
Test medium pH 8 T24 hours	Mean	28.02	Test medium pH 8 T28 days	Mean	18.93
	S.D.	2.57		S.D.	0.56
	RSD%	9.15		RSD%	2.97
Test medium pH 8 T4 days	Mean	27.96	-
	S.D.	0.55
	RSD%	1.98

n.d.: lower than the Limit of Detection (L.O.D. = 0.50 µg/L for Zn).

The between-vessel variation was less than 20% recommended by OECD Series No. 29.

 

Conclusions:

After 28 days, 162.01 and 18.93 µg/L of zinc had been released from the test item at pH 6 and pH 8, respectively. A greater amount of zinc was released from the test item at pH 6. In test medium at pH 8 a slow decrease of zinc released during the test was observed (from 45.54 µg/L after 2 hours to 18.93 µg/L after 28 days). The decrease in zinc concentration in the test medium at pH 8 during the test is probably due to the oxidizing process.

Executive summary:

The transformation/dissolution test with Zinc silicate was conducted at a loading rate of 1 mg/L in two aqueous media at pH 6 and pH 8 (Pardo Martinez 2016). The study was performed according the OECD 29 guideline and is a GLP-compliant. This study is considered reliable without restrictions (Klimisch 1) and is suitable for use as a key study for this endpoint.

 

After 28 days, 162.01 and 18.93 µg/L of zinc had been released from the test item at pH 6 and pH 8, respectively. Considering an initial Zinc silicate load of 1 mg and a maximum possible zinc release of 597 µg/L (calculated from the test item composition) the test results indicate that a greater amount of zinc is released from the test item at pH 6. In test medium at pH 8 a slow decrease of zinc released during the test was observed (from 45.54 µg/L after 2 hours to 18.93 µg/L after 28 days). The decrease in zinc concentration in the test medium at pH 8 during the test is probably due to the oxidizing process.

Description of key information

Based on the results of the transformation/dissolution study, zinc silicate is more soluble in test medium at pH 6. After 28 days, 162.01 and 18.93 µg/L of zinc had been released from the test item at a loading rate of 1 mg/L at pH 6 and pH 8, respectively. A slow decrease of zinc released during the test from 45.54 µg/L after 2 hours to 18.93 µg/L after 28 days was observed in test medium at pH 8.

Key value for chemical safety assessment

Water solubility:

162.01 µg/L

at the temperature of:

20 °C

Additional information

The transformation/dissolution test with zinc silicate was conducted according to the OECD 29 guideline (Pardo Martinez 2016). TD tests are a standard method for assessing the solubility of poorly soluble metal substances and provide additional data that cannot be obtained from a standard OECD 105 water solubility study. This is a guideline, GLP-compliant stud and is considered reliable without restrictions (Klimisch 1). It is suitable for use as a key study for this endpoint.

 

In the 28-day transformation/dissolution test with Zinc silicate, 162.01 and 18.93 µg/L of zinc had been released from the test item after 28 days at pH 6 and pH 8, respectively. Considering an initial Zinc silicate load of 1 mg/L and a maximum possible zinc release of 597 µg/L (calculated from the test item composition) the test results indicate that a greater amount of zinc is released from the test item at pH 6. In test medium at pH 8 a slow decrease of zinc released during the test was observed (from 45.54 µg/L after 2 hours to 18.93 µg/L after 28 days). The decrease in zinc concentration in the test medium at pH 8 during the test is probably due to the oxidizing process.