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Endpoint:
additional physico-chemical information
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
23 January 2008 - 29 May 2008
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study conducted in compliance with GLP to appropriate OECD and EU study guideline. Although the study is conducted upon the Zinc Hydroxystannate it is anticipated that the substances would behave identically in the aqueous environment, none the less the reliability rating of the study has been adjusted accordingly.
Qualifier:
according to
Guideline:
other: Annex 10 of the United Nations Globally Harmonised System of Classification and Labelling of Chemicals (GHS), First revised edition, 2005(ST/SG/AC. 10/30/Rev. 1).
GLP compliance:
yes (incl. certificate)
Endpoint investigated:
other: transformation/dissolution in aqueous media

SCREENING TRANSFORMATION/DISSOLUTION TEST

The zinc calibration was observed to be first order and the data are shown in the following table:

Table 5: Zinc Calibration

1st Order Curve

Zinc (Calibration 1 - pH 5.5 / 6.0)

Zinc (Calibration 2 - pH 7.0 / 8.5)

Slope

1.52 x 105

1.55 x 105

Intercept

4.33 x 103

3.48 x 103

Correlation coefficient (r)

0.999

0.999

The tin calibration was observed to be second order in the range 0 to 1.0 mg/L, but first order over the range of 0 to 0.2 mg/L. The first order calibration was used to calculate the tin concentration in the samples and the data obtained from this reduced calibration range are shown in the following table:

Table 6: Tin Calibration

1st Order Curve

Tin (Calibration 1 - pH 5.5 / 6.0)

Tin (Calibration 2 - pH 7.0 / 8.5)

Slope

3.11 x 105

3.12 x 105

Intercept

5.16 x 103

3.05 x 103

Correlation coefficient (r)

0.997

0.999

Concentrations in Buffered Aqueous Media

The concentrations of dissolved zinc and tin in the buffered aqueous media at a single loading of 100 mg/L shaken over a period of 24 hours are shown in the following table:

Table 7: Concentrations of Dissolved Zinc and Tin in Buffered Aqueous Media

Solution pH

Mean Concentration (mg/L)

Zinc

Tin

5.5

0.29

0.03

6.0

0.09

ND*

7.0

ND

ND

8.5

ND

ND

 

*ND: None Detected, <LOD (0.01/L)

FULL TRANSFORMATION/DISSOLUTION TEST

Short Term Test - 7 Day

The concentrations of dissolved zinc and tin in pH 6.0 buffered aqueous media at loadings of 100 mg/L and 10 mg/L shaken over a period of 7 days are shown in the following table.

Table 8: Concentrations of Dissolved Zinc and Tin in Buffer Solution at pH 6

Time Period

Mean Concentration

Zinc

Tin

100 mg/L

2 hours

0.03

0.01

4 hours

0.04

0.02

24 hours

0.05

0.0

98 hours

0.17

0.08

168 hours

0.09

0.01

10 mg/L

2 hours

0.02

ND*

4 hours

0.01

0.01

24 hours

0.02

ND

98 hours

0.06

0.01

168 hours

0.06

0.01

Long Term Test - 28 Day

The concentrations of dissolved zinc and tin in pH 5.5 buffered aqueous media at a loading of 10 mg/L shaken over a period of 28 days are shown in the following table

 

Table 9: Concentrations of Dissolved Zinc and Tin in Buffer Solution at pH 5.5

Solution

Zinc

Tin

Concentration (mg/L)

Mean Concentration (mg/L)

Concentration (mg/L)

Mean Concentration (mg/L)

Sample A, 10 mg/L, 28 days

0.23

0.20

ND*

ND

Sample B, 10 mg/L, 28 days

0.20

ND

Sample C, 10 mg/L, 28 days

0.17

ND

 

Discussion

The Annex 10 guidelines specify that the total organic content (TOC) of the aqueous media should not exceed 2.0 mg/L. The TOC was determined on the pH 6.0 buffered aqueous media and found to be approximately 300 mg/L. The TOC was not determined on the pH 5.5 buffered aqueous media as this buffer was organic in nature. Consultation with the Environment Agency had concluded that pH consistency was of greater importance than the integrity of the aqueous media, and it was agreed that the test should continue to completion.

The kinetics of the study could not be determined since there was insufficient data at levels above the limit of quantification (LOQ: 0.1 mg/L for zinc, 0.05 mg/L for tin).

The limit of quantification for each analyte was based on the lowest validated level. Since the majority of the data was below these levels, quantitative data has been presented only for all results greater than the limit of detection (0.01 mg/L).

Conclusion

The maximum concentrations of dissolved zinc and tin observed in the short term (7 day) and long term (28 day) transformation/dissolutions tests are shown in the following table.

Table 10: Maximum Concentrations of Dissolved Zinc and Tin

Sample

Zinc Concentration (mg/L)

Tin Concentration (mg/L)

Short Term (7 day) 100 mg/L

0.09

0.01

Short Term (7 day) 10 mg/L

0.06

0.01

Long Term (28 day) 10 mg/L

0.23

None detected*

* None detected, <LOD (0.01 mg/L)

There was insufficient data for transformation/dissolution kinetics to be calculated.

Conclusions:
There were insufficient data for transformation/dissolution kinetics to be calculated.
Executive summary:

The determination was carried out according to Annex 10 of the United Nations Globally Harmonised System of Classification and Labelling of Chemicals (GHS), First revised edition, 2005(ST/SG/AC.10/30/Rev. 1).

The principles of the test are based on a simple experimental procedure of agitation of various quantities of the test substance in a pH buffered aqueous medium. Sampling and analysing the solutions is performed at specific time intervals to determine the concentrations of dissolved metal ions in the water. The test comprises a screening transformation/dissolution test, a full transformation/dissolution test and method validation.

Screening transformation/dissolution test:

The concentrations of dissolved zinc and tin in the buffered aqueous media at a single loading of 100 mg/L, shaken over a period of 24 hours, are shown in the following table:

Solution pH

Mean Concentration (mg/L)

Zinc

Tin

5.5

0.29

0.03

6.0

0.09

ND*

7.0

ND

ND

8.5

ND

ND

 * None Detected <LOD (0.01 mg/L)

Full transformation/dissolution test:

 

Based on the data obtained from the screening test, the full transformation/dissolution test was performed in pH 6.0 buffered aqueous media at loadings of 10 mg/L and 100 mg/L for the short term test (7 day), and in pH 5.5 buffered aqueous media at a loading of 10 mg/L for the long term test (28 day).

A loading rate of 1 mg/L was excluded from the full test since it was demonstrated in the screening test that the solubility of the test material in low pH aqueous buffer solutions was equivalent to approximately to 1 mg/L. For this reason, the long term test (28 day) was performed at a loading rate of 10 mg/L.

The maximum concentrations of dissolved zinc and tin observed in the short term (7 day) and the long term (28 day) transformation/dissolution tests are shown in the following table:

Sample

Zinc Concentration (mg/L)

Tin Concentration (mg/L)

Short Term (7 day) 100 mg/L

0.09

0.01

Short Term (7 day) 10 mg/L

0.06

0.01

Long Term (28 day) 10 mg/L

0.23

None detected*

* None detected, <LOD (0.01 mg/L)

There were insufficient data for transformation/dissolution kinetics to be calculated.

 

Method Validation:

 

The analytical method for the determination of zinc and tin in the buffered aqueous media (ISO 6341) has been validated with the respect to linearity, accuracy, precision (repeatability) and precision (replicate analysis), limit of detection and limit of quantification.

The results of the validation are shown in the following table:

Parameter

Analyte

Zinc

Tin

Linearity

Concentration range (mg/L)

0 to 1.0

0 to 0.2

Slope

1.22 x 105

2.35 x 105

Intercept

185

2.05 x 103

Correlation coefficient (r)

0.999

0.999

Accuracy (%) (Precision (% RSD)):

pH 5.5, 0.5 mg/L Zn, 0.1 mg/L Sn

94 (2.87)

84 (14.3)

pH 5.5, 0.1 mg/L Zn, 0.05 mg/L Sn

93 (3.27)

87 (10.9)

pH 5.5, 0.05 mg/L Zn, 0.02 mg/L Sn

138 (58.5)

40 (93.5)

pH 6.0, 0.1 mg/L Zn, 0.1 mg/L Sn

105 (5.36)

88 (20.6

pH 6.0, 0.05 mg/L Zn, 0.05 mg/L Sn

96 (4.77)

58 (13.1)

pH 6.0, 0.02 mg/L Zn, 0.02 mg/L Sn

200 (25.3)

56 (60.0)

Precision (replicate analysis):

RSD (%)

4.51

8.01

 

Limit of Detection (mg/L)

0.01

0.01

Limit of Quantification (mg/L)

0.1

0.05

Description of key information

After a full transformation/dissolution test there were insufficient data for transformation/dissolution kinetics to be calculated.

Additional information

The determination of transformation/dissolution was carried out according to Annex 10 of the United Nations Globally Harmonised System of Classification and Labelling of Chemicals (GHS), First revised edition, 2005(ST/SG/AC.10/30/Rev. 1).

The principles of the test are based on a simple experimental procedure of agitation of various quantities of the test substance in a pH buffered aqueous medium. Sampling (and analysis) of the solutions is performed at specific time intervals to determine the concentrations of dissolved metal ions in the water. The test comprises a screening transformation/dissolution test, a full transformation/dissolution test and method validation.

However, after the full transformation/dissolution test there were insufficient data for transformation/dissolution kinetics to be calculated.