Bis(dodecylthio)dioctylstannane

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 September 2016 to 20 September 2017

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Version / remarks:

2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Deviations:

no

GLP compliance:

no

Remarks:

(this is not a toxicological or ecotoxicological test)

Radiolabelling:

not specified

Analytical monitoring:

yes

Details on sampling:

Sample preparation: 370 µL/ 330 µL toluene-d8 (10 mg/mL CrAcAc)

Buffers:

pH 1.2: HCl 0.1 M
pH 4.0: HCl/NaCl/Citric acid
pH 7.0: Na2HPO4/NaH2PO4
pH 9.0: H3BO3/KCl/NaOH

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 250 mL Erlenmeyer flask with ground stopper

HIGH PH TESTING (pH 4.0, 7.0, 9.0)
- The test material was used without a co-solvent or a detergent.
- 1 g (1.3 mMol) of the test material was added to 100 mL of the respective buffer solution in a 250 mL Erlenmeyer flask.
- The flask was closed with a stopper and heated in a heating cabinet for 5 days (120 hours) at 50°C.
- The mixture was stirred by a magnetic stirrer using a 40 x 7 mm stir bar at approx. 100 rpm.
- After the pre-determined reaction time, the solution was allowed to cool down to room temperature; 10 mL of each reaction mixture was taken by a syringe and placed in a headspace glass for TOC analysis. The rest of each reaction mixture was extracted with 20 mL hexane, the phases were separated using a separatory funnel. The organic phase was transferred into a pre-weighed flask and the solvent was removed in a rotary evaporator (< 40°C, 10 mbar). The weight difference was recorded for the mass balance, and the samples were analysed by 119Sn-NMR.

GASTRIC PH TESTING (pH 1.2/ 37 °C)
- The test material was used without a co-solvent or a detergent.
- 1 g (1.3 mMol) of the test material was added to 100 mL of 0.1 M aqueous solution of hydrochloric acid that was preheated to 37 °C in a 250 mL Erlenmeyer flask with ground in stopper.
- The flask was closed with a stopper and heated on a heating cabinet for 4 hours at 37°C.
- The mixture was stirred by a magnetic stirrer using a 40 x 7 mm stir bar at approximately 100 rpm.
- After the pre-determined exposure time, the solution was allowed to cool down to room temperature; extracted 2 times with 25 mL hexane; the phases were separated using a separatory funnel. The organic phase was transferred into flask, and the solvent was removed in a rotary evaporator (< 40°C, 10 mbar). The sample was analysed by 119Sn-NMR.

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

100 other: %

Remarks:

The test material was used without a solvent.

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

100 other: %

Remarks:

The test material was used without a solvent.

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

100 other: %

Remarks:

The test material was used without a solvent.

Duration:

4 h

pH:

1.2

Temp.:

37 °C

Initial conc. measured:

100 other: %

Remarks:

The test material was used without a solvent.

Number of replicates:

1

Positive controls:

no

Negative controls:

no

Transformation products:

yes

Remarks:

Chloro, dodecylthio dioctylstannane (DOT-SLau Cl)

% Recovery:

99

pH:

4

Temp.:

50 °C

Duration:

5 d

% Recovery:

102

pH:

7

Temp.:

50 °C

Duration:

5 d

% Recovery:

99

pH:

9

Temp.:

50 °C

Duration:

5 d

Key result

pH:

4

Temp.:

50 °C

DT50:

> 1 yr

Remarks on result:

other: hydrolytically stable

Key result

pH:

7

Temp.:

50 °C

DT50:

> 1 yr

Remarks on result:

other: hydrolytically stable

Key result

pH:

9

Temp.:

50 °C

DT50:

> 1 yr

Remarks on result:

other: hydrolytically stable

Details on results:

HYDROLYSIS AT PH 4,7 AND 9
- Samples of the test material were added to the respective buffer solutions at 50°C for 5 days (120 h). At no pH value the 119Sn-NMR spectra of the extracted reaction products show signs of hydrolysis.
- The half-life time of the test material under the conditions of the study is > 1 year. The test material is considered as hydrolytically stable.

HYDROLYSIS AT PH 1.2
- 1 g (1.3 mMol) of the test material was added to an excess 0.1 M hydrochloric acid at 37°C for 4 hours and extracted with hexane after cooling down to room temperature. The 119Sn-NMR spectrum of the organic extract shows a decrease of the products peak and an increase of the breakdown product, the monochloride of the substance DOT(-SLau)Cl.
- A small side sharp side peak in the broad signal for the monochloride appears at 144 ppm and cannot be reliably quantified or assigned to a organotin substance. The chemical shift points to a disulfur bridged organotin compound. No signal for DOTC could be identified in the 119Sn spectrum.
- The composition of the test material hydrolysate at pH 1.2 based on 119Sn-NMR analysis was:
DOT(-SLau)2 30 Mol% and DOT(-SLau)Cl 70 Mol%.
- In order to assure no DOTC has been formed, the NMR sample was spiked with DOTC. The spectra showed a further reaction between the residual dioctyltin-di-thiolaurate and the dioctyltin dichloride resulting in additional dioctyltin-monochloro mono thiolaurate according to the following equation:
Oc2Sn(S-Lau)2 + Oc2SnCl2 = 2 Oc2Sn(SLau)Cl

MASS BALANCE RECIVERY RATES
pH 4: 100 %
pH 7: 98 %
pH 9: 100 %
pH 1.2: 103 %

ATOMIC ABSORPTION SPECTOMETRY
- The aqueous phases of the low pH hydrolysis has been analysed after extraction with hexane by AAS and contained less than 5 mg/L Sn.

Validity criteria fulfilled:

not specified

Conclusions:

Under the conditions of this study, the test material was is hydrolytically stable at pH 4, 7 and 9. At pH 1.2 the only identifiable breakdown product was the monochloride of the test material chloro, dodecylthio dioctylstannane (DOT-SLau Cl). It appears besides the unreacted test material. DOTC was not detected in the organic extract. The high recovery of substances in the hexane extract and the low tin content of the aqueous phase (< 5 mg/L) indicate that no reaction products remained in the aqueous phase of the experiment.

Executive summary:

The hydrolysis of the test material as a function of pH was investigated in accordance with the standardised guidelines OECD 111 and EU Method C.7.

The stability of the test material was investigated at pH 4, 7 and 9 and pH 1.2 using NMR spectroscopy.

The study showed that the test material was hydrolytically stable at pH 9, 7 and 4. After 5 days of hydrolysis at 50 °C less than 10 % of the test material was hydrolysed (t 0.5 at 25 °C > 1 year).

At simulated gastric conditions (0.1 M HCl /pH 1.2 /37°C/ 4 h) the only identifiable breakdown product was the monochloride of the test material chloro, dodecylthio dioctylstannane (DOT-SLau Cl). It appears besides the unreacted test material. DOTC was not detected in the organic extract.

A spiking experiment confirmed non-presence of DOTC in the reaction mixture and showed that DOTC reacts with the test material forming it’s monochloride.

The high recovery of substances in the hexane extract and the low tin content of the aqueous phase (< 5 mg/L) indicate that no reaction products remained in the aqueous phase of the experiment.

Description of key information

Under the conditions of this study, the test material was is hydrolytically stable at pH 4, 7 and 9.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

50 °C

Additional information

The hydrolysis of the test material as a function of pH was investigated in accordance with the standardised guidelines OECD 111 and EU Method C.7.

The stability of the test material was investigated at pH 4, 7 and 9 and pH 1.2 using NMR spectroscopy.

The study showed that the test material was hydrolytically stable at pH 9, 7 and 4. After 5 days of hydrolysis at 50 °C less than 10 % of the test material was hydrolysed (t 0.5 at 25 °C > 1 year).