8,8-dioctyl-1,4-dioxa-7,9-dithia-8-stannacycloundecane-5,11-dione

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 07 November 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 (1.8 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 (1.8 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:

not specified

Remarks:

DOTO complex

% Recovery:

73

pH:

4

Temp.:

50 °C

Duration:

5 d

% Recovery:

80

pH:

7

Temp.:

50 °C

Duration:

5 d

% Recovery:

92

pH:

9

Temp.:

50 °C

Duration:

5 d

Key result

Remarks on result:

other: Half life not reported

Details on results:

HYDROLYSIS AT PH 4, 7 AND 9
- The 119Sn spectrum of the unhydrolysed test material shows a signal group between 88 – 100 ppm which can be attributed to different species of DOT-EGMA which is a UVCB substance. The main peak appears at 88 ppm, attributed to DOT-EGMA, the smaller side peaks represent different coordinations of the bi-funtional ligand EGMA with the dioctyltin unit. A sharp signal at ~ -45 ppm is attributed to DOTTG which is present in UVCB substance as side reaction product or breakdown product. The integrals of the spectrum show a ratio of 86:12 Mol % DOT-EGMA : DOTTG
- At pH 4 and 7 the 119Sn-NMR spectra of the hydrolysates show a shift of intensities from the signal group between 88-100 ppm towards the DOTTG peak at -45 ppm. The difference in intensities is between 16 and 21 %.
- At pH 9 a further shift of intensities occurs together with the broadening of the DOTTG signal. Two additional broad signals of minor intensity show at -0.6 ppm and -53 ppm.
- The broadening of peaks in this area indicates the formation of a DOTO complex resp. a solution of DOTO in DOTTG.
- The formation of such DOTO complex structures have been postulated for the breakdown of other Organotin carboxylates.

HYDROLYSIS AT PH 1.2
- In the 119Sn-NMR spectrum of the organic extract the signal group between 88-100 ppm decreased in intensity to 12 Mol %.
- New peaks appear at 49 ppm, 42 and 41 ppm. They are typical for the monochloroesters of thiocarboxylates.
- The peak representing DOTTG at -45 ppm increased in intensity from 12 to 30 Mol%. This supports that also a breakdown of the EGMA ligand occurs.
- Some smaller peaks between -40 and 0 ppm can not be assigned unequivocally to an organotin species.
- No DOTC was formed under the conditions of the study

MASS BALANCE RECOVERY RATES
pH 4: 73 %
pH 7: 80 %
pH 9: 92 %
pH 1.2: 85 %

ATOMIC ABSORPTION SPECTOMETRY
- The aqueous phase of the low pH hydrolysis has been analysed after extraction with hexane by AAS and contained < 5mg/L Sn. So the formation of an organotin substance better soluble in water than in hexane can be excluded.

Validity criteria fulfilled:

not specified

Conclusions:

After 5 days of hydrolysis at 50 °C at pH 4, 7 ,9 there was an increase of DOTTG in the extracted hydrolysate. This suggests that the breakdown of the test material includes the hydrolysis of the EGMA ligand.
At pH 9 the DOTTG peak was broadened, which suggests the formation of DOTO.
At simulated gastric conditions (0.1 M HCl /pH 1.2 /37 °C/ 4 h) the extracted test material decreased to 17 Mol %. The DOTTG content of the extracted hydrolysate increased from 12 to 30 Mol%. Three new signals at 41, 42 and 49 ppm are typical for the monochloroesters of thiocarboxylates.
No signals were formed during simulated gastric hydrolysis which can be attributed to DOTC.
The tin content in the aqueous phase of the hydrolysis remained under the detection limit of < 5 mg/L in AAS. Thus the formation of a water soluble organotin species can be excluded.

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 test material is a UVCB type substance resulting from the reaction of a bi-functional ligand to with dioctyltin unit allowing all different kind of coordinations. Thus the interpretation of the hydrolytical behaviour of this test material is rough and has to consider groups of possible UVCB constituents.

After 5 days of hydrolysis at 50°C at pH 4, 7 ,9 there was an increase of DOTTG in the extracted hydrolysate. This suggests that the breakdown of the test material includes the hydrolysis of the EGMA ligand.

At pH 9 the DOTTG peak was broadened, which suggests the formation of DOTO.

At simulated gastric conditions (0.1 M HCl /pH 1.2 /37 °C/ 4 h) the extracted test material decreased to 17 Mol %. The DOTTG content of the extracted hydrolysate increased from 12 to 30 Mol%. Three new signals at 41, 42 and 49 ppm are typical for the monochloroesters of thiocarboxylates.

No signals were formed during simulated gastric hydrolysis which can be attributed to DOTC.

The tin content in the aqueous phase of the hydrolysis remained under the detection limit of < 5 mg/L in AAS. Thus the formation of a water soluble organotin species can be excluded.

Description of key information

After 5 days of hydrolysis at 50°C at pH 4, 7 ,9 there was an increase of DOTTG in the extracted hydrolysate. This suggests that the breakdown of the test material includes the hydrolysis of the EGMA ligand.

At pH 9 the DOTTG peak was broadened, which suggests the formation of DOTO.

At simulated gastric conditions (0.1 M HCl /pH 1.2 /37 °C/ 4 h) the extracted test material decreased to 17 Mol %. The DOTTG content of the extracted hydrolysate increased from 12 to 30 Mol%. Three new signals at 41, 42 and 49 ppm are typical for the monochloroesters of thiocarboxylates.

No signals were formed during simulated gastric hydrolysis which can be attributed to DOTC.

The tin content in the aqueous phase of the hydrolysis remained under the detection limit of < 5 mg/L in AAS. Thus the formation of a water soluble organotin species can be excluded.

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 study was awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch et al. (1997).

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

The test material is a UVCB type substance resulting from the reaction of a bi-functional ligand to with dioctyltin unit allowing all different kind of coordinations. Thus the interpretation of the hydrolytical behaviour of this test material is rough and has to consider groups of possible UVCB constituents.

After 5 days of hydrolysis at 50°C at pH 4, 7 ,9 there was an increase of DOTTG in the extracted hydrolysate. This suggests that the breakdown of the test material includes the hydrolysis of the EGMA ligand.

At pH 9 the DOTTG peak was broadened, which suggests the formation of DOTO.

At simulated gastric conditions (0.1 M HCl /pH 1.2 /37 °C/ 4 h) the extracted test material decreased to 17 Mol %. The DOTTG content of the extracted hydrolysate increased from 12 to 30 Mol%. Three new signals at 41, 42 and 49 ppm are typical for the monochloroesters of thiocarboxylates.

No signals were formed during simulated gastric hydrolysis which can be attributed to DOTC.

The tin content in the aqueous phase of the hydrolysis remained under the detection limit of < 5 mg/L in AAS. Thus the formation of a water soluble organotin species can be excluded.