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Environmental fate & pathways

Hydrolysis

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Endpoint:
hydrolysis
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Justification for type of information:
The target substance is a mono-constituent organotin substance that consists of a tin as central metal element with two octyl-ligands. The source substance Dioctyltin oxide (DOTO) (EC Number 212-791-1 and CAS 870-08-6) is also an organotin compound that has the identical structure elements as the target substance in respect of the tin-alkyl moiety.
According to WHO IPCS CIRCAD (2006) organotin compounds are characterized by a tin–carbon bond and have the general formula RxSn(L)(4−x), where R is an organic alkyl or aryl group and L is an organic (or sometimes inorganic) ligand. The organotin moiety is significant toxicologically. The anionic ligand influences physicochemical properties but generally has little or no effect on the toxicology.
Since the target substance and the source substances share the identical organotin moiety, and the organotin moiety is generally recognized as the relevant toxophore of organotins and the toxicity estimates (AE) respectively toxicity limits for organotins are expressed as tin, the overall ecotoxicity/systemic toxicity of the target can be interpolated by assessing the (eco-)toxicity of the source (WHO IPCS CIRCAD, 2006, BAUA AGS TRGS 900, 2014, Summer KH, Klein D and Greim H, 2003).
The purity of the source and target substance are expected to be similar, based on the manufacturing method. The impurity profile is not expected to have strong effects on substance properties and any impurity of (eco-)toxicological relevance of the source substances is expected to be present in the target substance. Consequently, the hazard profiles of the source substances, including those of their impurities, are intrinsically covered. Differences in impurities are not expected and thus do not have an impact on the (eco-)toxic properties.

References
BAUA (Bundesanstalt für Arbeitsschutz und Arbeitsmedizin (Federal Institute for Occupational Safety and Health)) AGS (Ausschuss für Gefahrstoffe (Committee on Hazardous Substances)) TRGS (Technical Rules for Hazardous Substances) 900 (2014). Begründung zu n-Octylzinnverbindungen, April 2014.
Summer KH, Klein D, Griem H (2003). Ecological and toxicological aspects of mono- and disubstituted methyl-, butyl-, octyl-, and dodecyltin compounds - Update 2002. GSF National Research Center for Environment and Health, Neuherberg, for the Organotin Environmental Programme (ORTEP) Association.
World Health Organization (WHO) International Programme on Chemical Safety (IPCS) Concise International Chemical Assessment Document (CICAD) 73 Mono- and disubstituted methyltin, butyltin, and octyltin compounds (2006). Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organization, and the World Health Organization, and produced within the framework of the Inter-Organization Programme for the Sound Management of Chemicals
Reason / purpose for cross-reference:
read-across source
Details on results:
The test substance could not be detected as no detectable amount could be dissolved in any solvent.
Endpoint:
hydrolysis
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Justification for type of information:
The target substance is a mono-constituent organotin substance that consists of a tin as central metal element with two octyl-ligands. The source substance Dioctyltin oxide (DOTO) (EC Number 212-791-1 and CAS 870-08-6) is also an organotin compound that has the identical structure elements as the target substance in respect of the tin-alkyl moiety.
According to WHO IPCS CIRCAD (2006) organotin compounds are characterized by a tin–carbon bond and have the general formula RxSn(L)(4−x), where R is an organic alkyl or aryl group and L is an organic (or sometimes inorganic) ligand. The organotin moiety is significant toxicologically. The anionic ligand influences physicochemical properties but generally has little or no effect on the toxicology.
Since the target substance and the source substances share the identical organotin moiety, and the organotin moiety is generally recognized as the relevant toxophore of organotins and the toxicity estimates (AE) respectively toxicity limits for organotins are expressed as tin, the overall ecotoxicity/systemic toxicity of the target can be interpolated by assessing the (eco-)toxicity of the source (WHO IPCS CIRCAD, 2006, BAUA AGS TRGS 900, 2014, Summer KH, Klein D and Greim H, 2003).
The purity of the source and target substance are expected to be similar, based on the manufacturing method. The impurity profile is not expected to have strong effects on substance properties and any impurity of (eco-)toxicological relevance of the source substances is expected to be present in the target substance. Consequently, the hazard profiles of the source substances, including those of their impurities, are intrinsically covered. Differences in impurities are not expected and thus do not have an impact on the (eco-)toxic properties.

References
BAUA (Bundesanstalt für Arbeitsschutz und Arbeitsmedizin (Federal Institute for Occupational Safety and Health)) AGS (Ausschuss für Gefahrstoffe (Committee on Hazardous Substances)) TRGS (Technical Rules for Hazardous Substances) 900 (2014). Begründung zu n-Octylzinnverbindungen, April 2014.
Summer KH, Klein D, Griem H (2003). Ecological and toxicological aspects of mono- and disubstituted methyl-, butyl-, octyl-, and dodecyltin compounds - Update 2002. GSF National Research Center for Environment and Health, Neuherberg, for the Organotin Environmental Programme (ORTEP) Association.
World Health Organization (WHO) International Programme on Chemical Safety (IPCS) Concise International Chemical Assessment Document (CICAD) 73 Mono- and disubstituted methyltin, butyltin, and octyltin compounds (2006). Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organization, and the World Health Organization, and produced within the framework of the Inter-Organization Programme for the Sound Management of Chemicals
Reason / purpose for cross-reference:
read-across source
No.:
#1
Details on hydrolysis and appearance of transformation product(s):
At study initiation (0 h sampling) very high concentrations of the transformation products were observed. Analysis of 0 h samplings were performed within 4.5 hours after application. For the C12 carboxylic acid, transformation rates significantly above 50 % of the applied test item were calculated indicating a rapid aqueous transformation. On further sampling intervals, a steady state or even a reduction of the carboxylic acid concentrations were observed. In all samples a white precipitate was observed and removed before analysis.
Endpoint:
hydrolysis
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Justification for type of information:
The target substance is a mono-constituent organotin substance that consists of a tin as central metal element with two octyl-ligands. The source substance Dioctylbis(pentane-2,4-dionato-O,O')tin (EC No. 483-270-6, CAS No. 54068-28-9) is also an organotin compound that has the identical structure elements as the target substance in respect of the tin-alkyl moiety.
According to WHO IPCS CIRCAD (2006) organotin compounds are characterized by a tin–carbon bond and have the general formula RxSn(L)(4−x), where R is an organic alkyl or aryl group and L is an organic (or sometimes inorganic) ligand. The organotin moiety is significant toxicologically. The anionic ligand influences physicochemical properties but generally has little or no effect on the toxicology.
Since the target substance and the source substances share the identical organotin moiety, and the organotin moiety is generally recognized as the relevant toxophore of organotins and the toxicity estimates (AE) respectively toxicity limits for organotins are expressed as tin, the overall ecotoxicity/systemic toxicity of the target can be interpolated by assessing the (eco-)toxicity of the source (WHO IPCS CIRCAD, 2006, BAUA AGS TRGS 900, 2014, Summer KH, Klein D and Greim H, 2003).
The purity of the source and target substance are expected to be similar, based on the manufacturing method. The impurity profile is not expected to have strong effects on substance properties and any impurity of (eco-)toxicological relevance of the source substances is expected to be present in the target substance. Consequently, the hazard profiles of the source substances, including those of their impurities, are intrinsically covered. Differences in impurities are not expected and thus do not have an impact on the (eco-)toxic properties.


References
BAUA (Bundesanstalt für Arbeitsschutz und Arbeitsmedizin (Federal Institute for Occupational Safety and Health)) AGS (Ausschuss für Gefahrstoffe (Committee on Hazardous Substances)) TRGS (Technical Rules for Hazardous Substances) 900 (2014). Begründung zu n-Octylzinnverbindungen, April 2014.
Summer KH, Klein D, Griem H (2003). Ecological and toxicological aspects of mono- and disubstituted methyl-, butyl-, octyl-, and dodecyltin compounds - Update 2002. GSF National Research Center for Environment and Health, Neuherberg, for the Organotin Environmental Programme (ORTEP) Association.
World Health Organization (WHO) International Programme on Chemical Safety (IPCS) Concise International Chemical Assessment Document (CICAD) 73 Mono- and disubstituted methyltin, butyltin, and octyltin compounds (2006). Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organization, and the World Health Organization, and produced within the framework of the Inter-Organization Programme for the Sound Management of Chemicals
Reason / purpose for cross-reference:
read-across source
No.:
#2
No.:
#1
Details on results:
Reaction rate and half lives for all tested conditions could not be assessed, as the hydrolysis reaction was completed within the first analysis. A transformation product was observed in the form of a white precipitate, immediately after adding the test material to the test system. This white amorphous material was assumed to be n-dioctyltin oxide and identity was confirmed in a separate study by X-ray spectroscopy.
Endpoint:
hydrolysis
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Justification for type of information:
The target substance is a mono-constituent organotin substance that consists of a tin as central metal element with two octyl-ligands. The source substance Dioctyltin oxide (DOTO) (EC Number 212-791-1 and CAS 870-08-6) is also an organotin compound that has the identical structure elements as the target substance in respect of the tin-alkyl moiety.
According to WHO IPCS CIRCAD (2006) organotin compounds are characterized by a tin–carbon bond and have the general formula RxSn(L)(4−x), where R is an organic alkyl or aryl group and L is an organic (or sometimes inorganic) ligand. The organotin moiety is significant toxicologically. The anionic ligand influences physicochemical properties but generally has little or no effect on the toxicology.
Since the target substance and the source substances share the identical organotin moiety, and the organotin moiety is generally recognized as the relevant toxophore of organotins and the toxicity estimates (AE) respectively toxicity limits for organotins are expressed as tin, the overall ecotoxicity/systemic toxicity of the target can be interpolated by assessing the (eco-)toxicity of the source (WHO IPCS CIRCAD, 2006, BAUA AGS TRGS 900, 2014, Summer KH, Klein D and Greim H, 2003).
The purity of the source and target substance are expected to be similar, based on the manufacturing method. The impurity profile is not expected to have strong effects on substance properties and any impurity of (eco-)toxicological relevance of the source substances is expected to be present in the target substance. Consequently, the hazard profiles of the source substances, including those of their impurities, are intrinsically covered. Differences in impurities are not expected and thus do not have an impact on the (eco-)toxic properties.

References
BAUA (Bundesanstalt für Arbeitsschutz und Arbeitsmedizin (Federal Institute for Occupational Safety and Health)) AGS (Ausschuss für Gefahrstoffe (Committee on Hazardous Substances)) TRGS (Technical Rules for Hazardous Substances) 900 (2014). Begründung zu n-Octylzinnverbindungen, April 2014.
Summer KH, Klein D, Griem H (2003). Ecological and toxicological aspects of mono- and disubstituted methyl-, butyl-, octyl-, and dodecyltin compounds - Update 2002. GSF National Research Center for Environment and Health, Neuherberg, for the Organotin Environmental Programme (ORTEP) Association.
World Health Organization (WHO) International Programme on Chemical Safety (IPCS) Concise International Chemical Assessment Document (CICAD) 73 Mono- and disubstituted methyltin, butyltin, and octyltin compounds (2006). Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organization, and the World Health Organization, and produced within the framework of the Inter-Organization Programme for the Sound Management of Chemicals
Reason / purpose for cross-reference:
read-across source
Details on results:
The IR spectrum of the hydrolysis product of the test material was analogous to that of dioctyltin oxide thereby confirming it as a hydrolysis product. The resolution of the NMR spectra was found to be insufficient.
Endpoint:
hydrolysis
Data waiving:
study technically not feasible
Justification for data waiving:
other:
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Not reported.
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
An internal company study conducted to a good scientific standard with a reasonable level of reporting. The test material DOTO (di-n-octyltin oxide) is in the same category of substances as the registration substance, as such it is considered acceptable to use a read-across approach to provide supporting information to address this endpoint.
Principles of method if other than guideline:
Electrospray ionisation mass spectrometry (ESI/MS) was used to determine whether dioctyltin compounds in water behave like dibutyltin compounds and form oxides relatively quickly. Additional observations were attempted using dioctyltin oxide.
GLP compliance:
not specified
Radiolabelling:
no
Analytical monitoring:
yes
Test performance:
The test substance could not be detected as no detectable amount could be dissolved in any solvent.
Transformation products:
not measured

The test substance could not be detected as no detectable amount could be dissolved in any solvent.

Validity criteria fulfilled:
not applicable
Remarks:
a non-standard method was used
Conclusions:
No results were presented as it was found that no detectable amount could be dissolved in any solvent.
Executive summary:

The aim of the study was to use electrospray ionisation mass spectrometry (ESI/MS) to determine whether dioctyltin compounds in water behave like dibutyltin compounds and form oxides relatively quickly. Although the read across substance was of interest in the study, difficulties arose preparing samples for analysis and the solubility of the test substance itself, as no detectable amount could be dissolved in any solvent. Furthermore, it was not possible to make standards for the test substance. Surrogate standards for other dioctyltin species were not possible as they gave multiple species when analysed and the relative ratio of the species changed with concentration. It could also not be determined whether all the species had the same ionisation effect as the oxide. No conclusion concerning the hydrolysis of the test substance could be determined in the present study.

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
23 March 2012 to 27 April 2012
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive, done to valid guidelines and the study was conducted under GLP conditions. Since the study was conducted with the read across substance di-n-octyltin dilaurate it has been assigned a reliability score of 2.
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Samples were taken at test initiation and at 8 points durin incubation times. All samples were diluted with acetonitrile (dilution factor 2) and centrifuged for 10 minutes before analysis. Further dilutions were necessary to a total dilution factor of 40 before analysis.
Buffers:
pH: 4.0
- Type of buffer: citrate buffer
- Composition of buffer: 90 mL of 0.1 mol/L NaOH were mixed with 500 mL 0.1 mol/L mono potassium citrate and diluted to 1000 mL with double distilled water.

pH: 7.0
- Type of buffer: phosphate buffer
- Composition of buffer: 296.3 mL of 0.1 mol/L NaOH were mixed with 500 mL 0.1 mol/L KH2PO4, diluted to 1000 mL with double distilled water.

pH: 9.0
- Type of buffer: borax buffer
- Composition of buffer: 213 mL of 0.1 mol/L NaOH were mixed with 500 mL 0.1 mol/L H3BO3 in 0.1 mol/L KCl, diluted to 1000 mL with double distilled water.

The buffer solutions were freshly prepared from chemicals with analytical grade or better quality. Buffers were purged with nitrogen for 5 minutes and the pH was checked to a precision of at least 0.1 at test temperature and sterilised through 0.2 µm.
Details on test conditions:
TEST MATERIAL
- Test concentration / mixture: 400 mg/L of the test material in the respective buffer solution.
- Co-solvent: tetrahydrofuran, 2 % (v/v).
- Stock solution: 20 g/L dried tetrahydrofuran.

TEST SYSTEM
- Test vessel: 15 mL centrifuge tubes.
- Test volume: 5 mL
- Application: A minimum of eight samples of the test mixture were prepared at test initiation by application of 100 µL of the test material stock solution into 4.9 mL of the respective buffer solution. After application the test vessel was sealed and the mixture was shaken vigorously. The time between test material application and transfer to thermostat / analysis did not exceed 5 minutes.
- Incubation time: 23 March 2012 to 13 April 2012.
- Temperature: 20, 30 and 50 °C ± 0.5 °C.
- Light: Photolytic effects were avoided by covering the thermostat.

VALIDITY CRITERIA
- The test temperature must remain within ± 0.5 °C.
- pH of the buffer solutions should be in the range of ± 0.1 pH units at test temperature.
- Sensitivity of the analytical methods should be sufficient to quantify test material concentrations at least down to a 90 % reduction of the initial concentration.
Duration:
432 h
pH:
4
Temp.:
20 °C
Initial conc. measured:
400 mg/L
Duration:
434 h
pH:
4
Temp.:
30 °C
Initial conc. measured:
400 mg/L
Duration:
435 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
400 mg/L
Duration:
432 h
pH:
7
Temp.:
20 °C
Initial conc. measured:
400 mg/L
Duration:
434 h
pH:
7
Temp.:
30 °C
Initial conc. measured:
400 mg/L
Duration:
435 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
400 mg/L
Duration:
432 h
pH:
9
Temp.:
20 °C
Initial conc. measured:
400 mg/L
Duration:
434 h
pH:
9
Temp.:
30 °C
Initial conc. measured:
400 mg/L
Duration:
435 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
400 mg/L
Number of replicates:
Single replicates, due to analytical reasons.
Positive controls:
no
Negative controls:
yes
Remarks:
Buffer solutions (pH value 4, 7 and 9)
Preliminary study:
A preliminary test at 50 °C for 120 h was not deemed to be necessary, as the test material is known to be unstable in aqueous test systems.
Test performance:
The regression graphs could not be calculated due to the rapid transformation of the test material. The test temperature did not differ more than ± 0.5 °C with the exception of the test conditions at 50 °C where an insignificant short term deviation was observed. The pH values if the buffer solutions were in the range of ± 0.1 pH at test temperature. Sensitivity of the analytical method was sufficient to quantify concentrations of the known transformation product, a carboxylic acid mixture of the test material at least down to 90 % of the applied test material.
Transformation products:
yes
No.:
#1
Details on hydrolysis and appearance of transformation product(s):
At study initiation (0 h sampling) very high concentrations of the transformation products were observed. Analysis of 0 h samplings were performed within 4.5 hours after application. For the C12 carboxylic acid, transformation rates significantly above 50 % of the applied test item were calculated indicating a rapid aqueous transformation. On further sampling intervals, a steady state or even a reduction of the carboxylic acid concentrations were observed. In all samples a white precipitate was observed and removed before analysis.

METHOD VALIDATION

- Linearity: The analytical system gave linear response in the calibration range of 1 - 10 mg/L. The coefficient of determination (R²) of the calibration graph was > 0.992.

- Limit of Quantification (LOQ): The LOQ of the analytical method was fixed at 2.4 mg/L. The LOQm, and 3.33 x LOQm were checked by means of accuracy.

- Specificity: Response of blank values of control samples from accuracy testing was significantly lower than 30 % of LOQm.

HYDROLYSIS RESULTS

- Check of pH value of the test system

Intended pH

Measured pH at

20 °C

30 °C

50 °C

4.0 ± 0.1

4.00

4.01

4.01

7.0 ± 0.1

7.03

7.02

7.02

9.0 ± 0.1

9.02

9.02

9.03

- Temperature monitoring:

Intended temperature (°C)

Measured temperature (°C)

Mean ± SD

min / max.

20.0 ± 0.1

20.0 ± 0.0 5

19.9 / 20.1

30.0 ± 0.1

30.1 ± 0.14

29.7 / 30.5

50.0 ± 0.1

50.0 ± 0.14

48.7 / 50.3

In the definitive test at target temperature of 50 °C the temperature was below the intended temperature range of 2 x 15 minutes of the total incubation time. Compared to the total incubation time this short term deviation could be regarded as negligible and had no significant influence on the study results.

TRANSFORMATION RESULTS

Table 1: Transformation rate of the carboxylic acids of the test material at test initiation

Carboxylic acid

Nominal conc. (mg/L)

pH 4

pH 7

pH 9

Calc. conc. (mg/L)

TR (%)

Calc. conc. (mg/L)

TR (%)

Calc. conc. (mg/L)

TR (%)

C12

129

92.3

71

90.7

70

73.4

57

C14

45.3

28.7

63

28.2

62

16.7

37

C16

20.3

8.5

42

9.9

49

(5.5)

27

C18 unsat.

17.8

6.3

36

6.4

36

(3.8)

21

TR = transformation rate

( ) = < LOQ

Table 2: Transformation results for the carboxylic acids of test material at pH 4

Hydrolysis Time (h)

Concentration (mg/L)

20 °C

0.00

C12

C14

C16

C18 unsat.

92.3

28.7

8.49

6.34

25.8

78.1

23.3

7.47

(4.09)

102

61.4

17.6

6.48

(4.22)

121

39.8

12.9

5.5

(4.28)

126

57.4

18.8

7.38

(4.82)

150

31.4

(8.05)

(3.92)

(2.57)

240

37.8

24.8

9.73

3.20

312

22.1

10.6

4.88

(2.07)

432

28.0

12.5

5.65

3.17

30 °C

0.00

92.3

28.7

8.49

6.34

26.8

64.8

21.8

8.34

(4.09)

103

39.3

(12.5)

(4.97)

(3.47)

123

33.4

11.7

5.19

(3.63)

127

26.0

(8.67)

(4.20)

(2.57)

151

54.0

7.64

(3.27)

(3.95)

242

17.7

(5.99)

3.83

(1.72)

313

15.7

(11.3)

6.21

(1.76)

434

12.3

(7.99)

(4.32)

(1.15)

50 °C

0.00

92.3

28.7

8.49

6.34

27.8

61.9

(8.61)

(4.32)

(2.84)

104

(1.5)

90.69)

(1.17)

(0.46)

124

(12.8)

(5.78)

(3.67)

(2.0)

128

(3.9)

(2.00)

(2.19)

(1.19)

151

(1.5)

(0.55)

(1.20)

(0.27)

243

(2.0)

(1.51)

(1.48)

(0.35)

314

(2.5)

(3.10)

(2.53)

(0.47)

435

(0.0)

(0.21)

(0.62)

0.0

( ) = < LOQ

Table 3: Transformation results for the carboxylic acids of test material at pH 7

Hydrolysis Time (h)

Concentration (mg/L)

20 °C

0.00

C12

C14

C16

C18 unsat.

90.7

28.2

9.91

6.36

25.8

57.1

(11.4)

(4.42)

(2.65)

102

48.1

(7.92)

(3.06)

(2.33)

121

66.0

14.9

6.48

(4.25)

126

64.2

16.6

6.61

(4.28)

150

41.4

(5.16)

(2.47)

(1.68)

240

110.6

22.8

8.52

3.11

312

79.9

(10.4)

(4.23)

(1.27)

432

94.3

17.8

7.57

(2.44)

30 °C

0.00

90.7

28.2

9.91

6.36

26.8

68.5

16.9

6.33

(3.82)

103

54.8

(11.5)

(5.28)

(3.28)

123

50.3

(11.9)

(5.43)

(2.95)

127

50.9

(11.8)

(4.63)

(2.74)

151

41.2

(8.33)

(3.52)

(2.52)

242

70.5

13.5

(5.77)

(1.71)

313

76.4

14.9

6.15

(1.90)

434

66.4

(12.5)

(5.68)

(1.46)

50 °C

0.00

90.7

28.2

9.91

6.36

27.8

50.3

(11.8)

5.50

(3.03)

104

30.8

(6.47)

(4.51)

(2.03)

124

28.5

(6.06)

(4.76)

(1.79)

128

33.6

(5.51)

(3.83)

(1.81)

151

(16.1)

(3.03)

(2.78)

(1.08)

243

26.1

(3.86)

(4.01)

(0.69)

314

25.7

(3.37)

(3.15)

(1.02)

435

26.7

(5.16)

(5.19)

(0.72)

( ) = < LOQ

Table 4: Transformation results for the carboxylic acids of test material at pH 9

Hydrolysis Time (h)

Concentration (mg/L)

20 °C

0.00

C12

C14

C16

C18 unsat.

73.4

16.7

(5.47)

(3.79)

25.8

66.4

13.9

(5.13)

(3.49)

102

83.1

19.0

8.40

4.98

121

70.7

15.6

6.98

(3.93)

126

72.5

15.2

6.39

(3.98)

150

69.7

(12.9)

(5.22)

(3.11)

240

81.3

13.2

(5.13)

(3.03)

312

69.9

13.8

5.68

(3.36)

432

69.9

(12.6)

(4.42)

(2.44)

30 °C

0.00

73.4

16.7

(5.47)

(3.79)

26.8

92.7

23.2

9.23

(5.15)

103

88.8

20.1

8.43

(4.33)

123

84.4

18.6

8.71

4.96

127

89.2

20.9

9.02

5.28

151

85.4

16.4

7.07

(3.85)

242

75.2

(12.5)

(5.37)

(3.06)

313

93.3

20.9

8.71

4.93

434

86.0

15.1

6.70

(3.22)

50 °C

0.00

73.4

16.7

(5.47)

(3.79)

27.8

90.7

20.1

9.48

5.50

104

77.4

13.8

7.20

(3.20)

124

76.4

15.1

9.76

(3.49)

128

76.2

15.8

10.44

(3.93)

151

82.1

16.6

9.94

(4.36)

243

83.1

(14.3)

9.57

(2.71)

314

84.2

15.4

10.99

(3.66)

435

81.1

(12.5)

9.91

(2.68)

( ) = < LOQ

VALIDITY CRITERIA

The validity criteria were fulfilled:

- The test temperature was 20 ± 0.5 °C.

- The pH of the buffer solutions were in the range of ± 0.1 pH at test temperature.

- The sensitivity of the analytical method was sufficient to quantify test material concentrations at least down to 90 % reduction of the initial concentration on basis of the known transformation product 2,4-pentadione.

Validity criteria fulfilled:
yes
Conclusions:
The reaction rate constants and half lives could not be calculated due to the fast hydrolysis of the test material. Under the conditions of the study the test material was immediately hydrolysed in the presence of water. Based on the obtained results is it concluded that the half life of the test material is below 4.5 hours for the main compound (C12 carboxylic acid homologues) and slightly above for the longer chain carboxylic acids homologues.
Executive summary:

Hydrolysis as a function of pH was investigated in a GLP study which was conducted in accordance with standardised guidelines OECD 111 and EU Method C.7. Testing was performed at pH 4, 7 and 9 at 20, 30 and 50 °C. The test material was applied at 400 mg/L (v/v) in each test system. For pH 4, 7 and 9, samples were taken at test initiation and at 8 spaced points. Buffer solutions were analysed at test initiation and at test termination and there was no analytical interference with the test material.

At the start of the study (0 h sampling) very high concentrations of the transformation products were observed. Analysis of 0 h samplings were performed within 4.5 hours after application. For the C12 carboxylic acid, transformation rates significantly above 50 % of the applied test material were calculated indicating a rapid aqueous transformation. On further sampling intervals, a steady state or even a reduction of the carboxylic acid concentrations were observed. In all samples a white precipitate was observed and removed before analysis. Therefore, it could be concluded that the test material will immediately be hydrolysed in the presence of water, therefore no reaction rate constants or half life values could be calculated. Based on the results obtained it could be concluded that the half life of the test material is below 4.5 hours for the main compound (C12 carboxylic acid homologue) and slightly above for the longer chain homologues.

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
23 November 2011
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive, done to valid guidelines and the study was conducted under GLP conditions. Since the study was conducted with the read across substance dioctylbis(pentane-2,4-dionate-O,O’)tin it has been assigned a reliability score of 2.
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Samples were taken at test initiation and every 10 minutes at least until plateau phase was reached.
Buffers:
pH: 4.0
- Type of buffer: citrate buffer
- Composition of buffer: 45 mL of 0.1 mol/L NaOH were mixed with 250 mL 0.1 mol/L mono potassium citrate and diluted to 500 mL with double distilled water.

pH: 7.0
- Type of buffer: phosphate buffer
- Composition of buffer: 148.15 mL of 0.1 mol/L NaOH were mixed with 250 mL 0.1 mol/L KH2PO4, diluted to 500 mL with double distilled water.

pH: 9.0
- Type of buffer: borax buffer
- Composition of buffer: 106.5 mL of 0.1 mol/L NaOH were mixed with 250 mL 0.1 mol/L H3BO3 in 0.1 mol/L KCl, diluted to 500 mL with double distilled water.

The buffer solutions were freshly prepared from chemicals with analytical grade or better quality. Buffers were purged with nitrogen for 5 minutes and the pH was checked to a precision of at least 0.1 at test temperature.
Details on test conditions:
TEST SYSTEM
- Test concentration: 0.1 % (v/v) of the test material in the respective buffer solution
- Application: Seven samples of the test mixture were prepared at test start by direct application of 10 µL of the test material into 10 mL of the respective buffer solution. After application the test vessel was sealed and the mixture was shaken vigorously. Each sample was filtrated through 0.2 RC syringe filter to detach precipitation. The time between test material application and transfer to thermostat / analysis did not exceed 5 minutes.
- Incubation times: 0, 10, 20, 30, 40, 50 and 60 minutes.
- Temperature: 20 ± 0.5 °C
- Light: Photolytic effects were avoided by covering the thermostat

CALCULATIONS
Plateau phase was reached when three subsequent samples with less than 10 % relative standard deviation were obtained.

VALIDITY CRITERIA
- The test temperature must remain within ± 0.5 °C
- pH of the buffer solutions should be in the range of ± 0.1 pH units at test temperature
- Sensitivity of the analytical methods should be sufficient to quantify test material concentrations at least down to a 90 % reduction of the initial concentration.
Duration:
60 min
Number of replicates:
Single replicates, due to analytical reasons.
Positive controls:
no
Negative controls:
yes
Remarks:
Buffer solutions (pH value 4, 7 and 9)
Test performance:
Reaction rate constants and half lives for all tested conditions could not be assessed, as the hydrolysis reaction was completed within the first two analyses. Taking the visual observation of the immediate precipitation into account, it could be assumed that the hydrolytical half life is significantly lower than the time needed for the first sampling (10 minutes). The hydrolytic half life of the test material was below the scope of the employed methodology. The observed precipitate was confirmed as the transformation product n-dioctyltin oxide.
Transformation products:
yes
No.:
#1
No.:
#2
Details on hydrolysis and appearance of transformation product(s):
Reaction rate and half lives for all tested conditions could not be assessed, as the hydrolysis reaction was completed within the first analysis. A transformation product was observed in the form of a white precipitate, immediately after adding the test material to the test system. This white amorphous material was assumed to be n-dioctyltin oxide and identity was confirmed in a separate study by X-ray spectroscopy.

METHOD VALIDATION

- Linearity: The analytical system gave linear response in the calibration range of 9.75 to 975 mg/L. The coefficient of determination (R²) of the calibration graph was ≥ 0.992.

- Limit of Quantification (LOQ): The LOQ of the analytical method was set to 29.3 mg 2,4-pentadione/L. The LOQ and 10 x LOQ were checked by means of accuracy.

- Repeatability of injections:

Serial no.

2,4-pentadione

9.75 mg/L

975 mg/L

1

142507

21520949

2

142188

21355238

3

148971

21429950

4

141568

21125524

5

147647

21168182

6

151764

21587619

Mean

145774

21364577

CV (%)

2.9

0.9

CV = Coefficient of variation

- Accuracy, precision and specificity

pH 4

Replicate

2,4-pentadione

1 x LOQ

10 x LOQ

Meas. Conc. (mg/L)

RR (%)

Meas. Conc. (mg/L)

RR (%)

1

31.751

108

289.585

99

2

31.054

106

298.771

102

3

31.857

109

300.010

102

4

31.885

109

300.614

103

5

31.444

107

299.603

102

Mean

31.598

108

297.717

102

pH 7

Replicate

2,4-pentadione

1 x LOQ

10 x LOQ

Meas. Conc. (mg/L)

RR (%)

Meas. Conc. (mg/L)

RR (%)

1

31.735

108

298.641

102

2

31.752

108

301.360

103

3

31.611

108

299.578

102

4

31.843

109

305.401

104

5

31.710

108

298.660

102

Mean

31.730

108

300.728

103

pH 9

Replicate

2,4-pentadione

1 x LOQ

10 x LOQ

Meas. Conc. (mg/L)

RR (%)

Meas. Conc. (mg/L)

RR (%)

1

31.547

108

294.695

101

2

31.930

109

295.018

101

3

31.687

108

295.160

101

4

31.924

109

286.505

98

5

91.892

109

287.594

98

Mean

31.796

109

291.794

100

RR = recovery rate

Response of blank samples for all validated matrices (buffer solutions pH 4, 7 and 9) was lower than 30 % of LOQ.

HYDROLYSIS RESULTS

- Check of pH value of the test system (20 °C)

Intended pH

Measured pH at 20 °C

4.0 ± 0.1

4.03

7.0 ± 0.1

7.02

9.0 ± 0.1

9.01

- Temperature monitoring: The minutely measured temperature was in good agreement with the nominal range throughout the study. The mean temperature was 20.2 ± 0.06 °C during the study (19.8 - 20.4 °C)

- Hydrolysis results for the test material

Hydrolysis time (min)

2,4-pentadione (mg/L)

pH 4

pH 7

pH 9

0

(216)

(225)

(204)

10

295

248

292

20

306

288

323

30

339

294

305

40

(342)

(318)

na

50

(337)

na

na

60

(325)

na

na

MV

313

277

307

SD

18.7

20.4

12.7

Bold = plateau phase

() = not used for calculation

MV = mean value of the last three samples

SD = standard deviation

- Mass balance:

The amount of 2,4-pentadione analysed at each sampling interval was used to calculate the respective amount of test material necessary to form this quantum of transformation product. A complete mass balance could not be established. It was assumed that the reduced, but reproducible, 2,4-pentadione content was caused by adsorption to the employed filter material, necessary for the elimination of precipitation. This was confirmed by representative IR measurements performed in a separate study.

Hydrolysis time (min)

Mass balance on 2,4-pentadione (% of the theoretical test material amount)

pH 4

pH 7

pH 9

0

52

54

49

10

71

60

71

20

74

70

78

30

82

71

74

Bold = plateau phase

VALIDITY CRITERIA

The validity criteria were fulfilled:

- The test temperature was 20 ± 0.5 °C

- The pH of the buffer solutions were in the range of ± 0.1 pH at test temperature

- The sensitivity of the analytical method was sufficient to quantify test material concentrations at least down to 90 % reduction of the initial concentration on basis of the known transformation product 2,4-pentadione.

Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of the study the test material was found to be highly hydrolytically unstable. The hydrolytical half life of the test material was below the scope of the methodology employed and could not be assessed following the principles of OECD guideline 111 and EU Method C.7 for all tested conditions.
Executive summary:

Hydrolysis as a function of pH was investigated in accordance with the standardised guidelines OECD 111 and EU Method C.7. Testing was performed at pH 4, 7 and 9 at 20 ± 0.5 °C. The test material was applied at 0.1 % (v/v) in test systems. Immediately after application, a reaction of the test material with the buffer was visually observed by formation of a white amorphous precipitate. Samples were taken at test initiation and every 10 minutes thereafter until a plateau phase was reached.

As a direct analysis of the test material from aqueous solution was not possible, the known transformation product 2,4-pentadione was analysed via HPLC-DAD. Quantification was performed against an external standard. The analytical method was validated with satisfactory results in regard to linearity, repeatability of injection, accuracy and specificity. Analyses indicated a plateau phase for the 2,4-pentadione content for all tested conditions after at least 10 minutes. A mass balance, based on analysed 2,4-pentadione could not be established. It was assumed that the reduced, but reproducible, 2,4-pentadione content was caused by adsorption to the employed filter material, necessary for the elimination of the precipitate. This was confirmed by representative IR measurements performed in a separate study.

Reaction rate constants and half lives for all tested conditions could not be assessed, as the hydrolysis reaction was completed within the first two analyses. Taking visual observation of the immediate precipitation into account, it could be assumed that the hydrolytical half life is significantly lower than the time needed for the first sampling (10 minutes).

Based on chemical deliberation, the transformation product (precipitate) was assumed to be n-dioctyl tin oxide. The identity was confirmed by X-ray spectroscopy in a separate study.

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Not reported
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: An internal company study conducted to a good scientific standard with a reasonable level of reporting. The study was conducted with the read across substance dioctylbis(pentane-2,4-dionate-O,O’)tin, and has been assigned a reliability score of 2.
Qualifier:
no guideline followed
Principles of method if other than guideline:
The hydrolysis products of the test material were investigated using IR and NMR spectroscopy.
GLP compliance:
not specified
Radiolabelling:
no

The IR spectrum of the hydrolysis product of the test material was analogous to that of dioctyltin oxide thereby confirming it as a hydrolysis product. The resolution of the NMR spectra was found to be insufficient.

Validity criteria fulfilled:
not applicable
Conclusions:
Under the conditions of the study dioctyltin oxide was found to be a hydrolysis product of tin, dioctylbis(2,4-pentanedionato-kO2,k)4)-, the condensation product of di-n-octyltin oxide den 2,4-pentanedione.
Executive summary:

The hydrolysis products of the test material were investigated using IR and NMR spectroscopy. During the study 10 g of test material was added to 90 g of distillated water and stirred for 48 hours at room temperature. On the border of the beaker and on the top of the water phase a white substance was formed. This substance was filtered out and washed several times with distilled water and later with n-hexane. After drying the substance for 24 hours at 50 °C in a vacuum it was analysed by IR and 119Sn-NMR spectroscopy.

The IR spectrum of the hydrolysis product of the test material was analogous to that of dioctyltin oxide thereby confirming it as a hydrolysis product. The resolution of the NMR spectra was found to be insufficient.

Therefore, under the conditions of the study dioctyltn oxide was found to be a hydrolysis product of tin, dioctylbis(2,4-pentanedionato-kO2,k)4)-, the condensation product of di-n-octyltin oxide den 2,4-pentanedione.

Description of key information

In accordance with Section 2 of Annex XI of Regulation (EC) No. 1907/2006 (REACH), it is considered justified to omit the hydrolysis study required under point 9.2.2.1 of Annex VIII on the grounds that testing is not technically feasible. 
Although the test material was determined to have a water solubility value of less than or equal to 1.19 x 10^-3 g/L, it has been considered that this value was a significant over-estimation, especially when contrasting the result with the calculated value of 4.7 x 10^-8 g/L, which suggests that the test material has a very low water solubility. Therefore, it was considered that the solution concentration required for the test, which would be half the saturated level at most, would be impractically low to perform the study as a sufficiently sensitive analytical method was not available.
The main functional groups in the components of the test material were a tin-ester complex, ester and alkene. The alkene groups would be unlikely to hydrolyse, especially as delocalisation with the ester groups would stabilise the double bond. Ester groups do undergo hydrolysis, but as for the alkene, they may be stabilised with the delocalisation effect. The tin-ester complex may have the potential to hydrolyse (dissociate) at environmentally relevant temperatures and pH, but as the test material has a very low solubility hydrolytic attack would be reduced.

Key value for chemical safety assessment

Additional information

Supporting information is provided in the form of four read across studies.


 


The first piece of supporting information is an internal company study conducted to a good scientific standard with a reasonable level of reporting, Yoder (2003). The study used a non-standard technique measuring the behaviour of dioctyltins in water by electrospray ionisation mass spectrometry (ESI/MS). Although the registered substance was a point of interest in the study, the poor solubility in both water and suitable solvents meant that the test substance was not present at a detectable level, and it was not possible to use a surrogate substance to create standards. No conclusions on the hydrolysis of the test substance could be drawn from the available data. The test material DOTO (di-n-octyltin oxide) is in the same category of substances as the registration substance, as such it is considered acceptable to use a read-across approach to provide supporting information to address this endpoint. In accordance with the criteria detailed by Klimisch (1997) the report was assigned a reliability score of 2 as it was performed and reported to a high standard.


 


In the second supporting study, hydrolysis as a function of pH was investigated in accordance with the standardised guidelines OECD 111 and EU Method C.7, Lange, 2012. Testing was performed at pH 4, 7 and 9 at 20 ± 0.5 °C. The test material was applied at 0.1 % (v/v) in test systems. Immediately after application, a reaction of the test material with the buffer was visually observed by formation of a white amorphous precipitate. Samples were taken at test initiation and every 10 minutes thereafter until a plateau phase was reached. As a direct analysis of the test material from aqueous solution was not possible, the known transformation product 2,4-pentadione was analysed via HPLC-DAD. Quantification was performed against an external standard. The analytical method was validated with satisfactory results in regard to linearity, repeatability of injection, accuracy and specificity. Analyses indicated a plateau phase for the 2,4-pentadione content for all tested conditions after at least 10 minutes. A mass balance, based on analysed 2,4-pentadione could not be established. It was assumed that the reduced, but reproducible, 2,4-pentadione content was caused by adsorption to the employed filter material, necessary for the elimination of the precipitate. This was confirmed by representative IR measurements performed in a separate study. Reaction rate constants and half lives for all tested conditions could not be assessed, as the hydrolysis reaction was completed within the first two analyses. Taking visual observation of the immediate precipitation into account, it could be assumed that the hydrolytical half life is significantly lower than the time needed for the first sampling (10 minutes). Based on chemical deliberation, the transformation product (precipitate) was assumed to be n-dioctyl oxide. The identity was confirmed by X-ray spectroscopy in a separate study.


 


The study report was conclusive, done to valid guidelines and was conducted under GLP conditions with a high level of reporting. Since the study was conducted with the read across substance dioctylbis(pentane-2,4-dionate-O,O’)tin it has been assigned a reliability score of 2 in accordance with the criteria of Klimisch (1997). As the test material is in the same category of substances as the registration substance, it is considered acceptable to use a read-across approach to provide supporting information to address this endpoint.


 


In the third uppoting study, hydrolysis as a function of pH was investigated in accordance with standardised guidelines OECD 111 and EU Method C.7. Testing was performed at pH 4, 7 and 9 at 20, 30 and 50 °C. The test material, di-n-octyltin dilaurate, was applied at 400 mg/L (v/v) in each test system. For pH 4, 7 and 9, samples were taken at test initiation and at 8 spaced points. Buffer solutions were analysed at test initiation and at test termination and there was no analytical interference with the test material.


At the start of the study (0 h sampling) very high concentrations of the transformation products were observed. Analysis of 0 h samplings were performed within 4.5 hours after application. For the C12 carboxylic acid, transformation rates significantly above 50 % of the applied test material were calculated indicating a rapid aqueous transformation. On further sampling intervals, a steady state or even a reduction of the carboxylic acid concentrations were observed. In all samples a white precipitate was observed and removed before analysis. Therefore, it could be concluded that the test material will immediately be hydrolysed in the presence of water, therefore no reaction rate constants or half life values could be calculated. Based on the results obtained it could be concluded that the half life of the test material is below 4.5 hours for the main compound (C12 carboxylic acid homologue) and slightly above for the longer chain homologues.


 


The study report was conclusive, done to valid guidelines and was conducted upder GLP conditions with a high level of reporting. Since the study was conducted with the read across substance di-n-octyltin dilaurate it has been assigned a reliability score of 2. As the test material is in the same category of substances as the registration substance, it is considered acceptable to use a read-across approach to provide supporting information to address this endpoint.


 


In the fourth supporting study, the hydrolysis products of the test material, tin, dioctylbis(2,4-pentanedionato-kO2,k)4)-, were investigated using IR and NMR spectroscopy. During the study 10 g of test material was added to 90 g of distillated water and stirred for 48 hours at room temperature. On the border of the beaker and on the top of the water phase a white substance was formed. This substance was filtered out and washed several times with distilled water and later with n-hexane. After drying the substance for 24 hours at 50 °C in a vacuum it was analysed by IR and 119Sn-NMR spectroscopy.


The IR spectrum of the hydrolysis product of the test material was analogous to that of dioctyltin oxide thereby confirming it as a hydrolysis product. The resolution of the NMR spectra was found to be insufficient.


Therefore, under the conditions of the study dioctyltn oxide was found to be a hydrolysis product of tin, dioctylbis(2,4-pentanedionato-kO2,k)4)-, the condensation product of di-n-octyltin oxide den 2,4-pentanedione.


 


These data are taken from an internal company study conducted to a good scientific standard with a reasonable level of reporting. Since the study was conducted with the read across substance dioctylbis(pentane-2,4-dionate-O,O’)tin, and has been assigned a reliability score of 2. As the test material is in the same category of substances as the registration substance, it is considered acceptable to use a read-across approach to provide supporting information to address this endpoint.