Butylhydroxyoxostannane

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

07 February 2018 to 09 May 2018

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)

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:

not required

Radiolabelling:

not specified

Analytical monitoring:

yes

Details on sampling:

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

Buffers:

Buffer Solutions
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: 2000 mL Erlenmeyer flask with ground in stopper

HIGH pH TESTING (pH 4.0, 7.0, 9.0)
- The test material was used without a co-solvent or a detergent.
- 20 g of the test material was added to 1000 mL of the respective buffer solution in a 2000 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/ 40 °C)
- The test material was used without a co-solvent or a detergent.
- 100 g of the test material was added to 5000 mL of 0.1 M aqueous solution of hydrochloric acid that was preheated to 40 °C in a 1000 mL stirred and tempered reactor.
- 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 a 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.:

40 °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:

monomeric monobutylstannonic acid

% Recovery:

> 90

pH:

4

Temp.:

50 °C

Duration:

5 d

% Recovery:

> 90

pH:

7

Temp.:

50 °C

Duration:

5 d

% Recovery:

> 90

pH:

9

Temp.:

50 °C

Duration:

5 d

Key result

pH:

4

Temp.:

25 °C

DT50:

> 1 yr

Type:

not specified

Key result

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

Type:

not specified

Key result

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

Type:

not specified

Details on results:

HYDROLYSIS AT pH 4.0, 7.0, and 9.0:
- All samples did not show significant changes in the 119Sn-NMR Spectrum
- The half-life time of the substance under the conditions of the study is > 1 year.
- The substance is considered hydrolytically stable at pH 4, 7, 9
- The signal propose a dimeric tetraorganodistannoxane structure. Those structures are formed following a stepwise hydrolysis of initially formed diorganotin hydroxides.

HYDROLYSIS AT pH 1.2
- 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(-Neo)Cl.
- The 119Sn-NMR spectrum shows only one signal in pH 1.2 not any longer the typical signal for dimeric MBTO (distannoxane). The single signal can be assigned to monomeric monobutylstannonic acid.

Validity criteria fulfilled:

not specified

Conclusions:

The study shows that the test material is hydrolytically stable at pH 4, 7, 9. After 5 days of hydrolysis at 50°C less than 10% of the test material was hydrolysed (half life at 25 °C > 1 year).
Under simulated gastric conditions (0.1 M HCl /pH 1.2 /40°C/ 4 h) the 119Sn-NMR spectrum shows only one signal in pH 1.2 not any longer the typical signal for dimeric MBTO (distannoxane). The single signal can be assigned to monomeric monobutylstannonic acid.

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 shows that the test material is hydrolytically stable at pH 4, 7, 9. After 5 days of hydrolysis at 50°C less than 10% of the test material was hydrolysed (half life at 25 °C > 1 year).

Under simulated gastric conditions (0.1 M HCl /pH 1.2 /40°C/ 4 h) the 119Sn-NMR spectrum shows only one signal in pH 1.2 not any longer the typical signal for dimeric MBTO (distannoxane). The single signal can be assigned to monomeric monobutylstannonic acid.

Description of key information

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

Under simulated gastric conditions (0.1 M HCl /pH 1.2 /40°C/ 4 h) the 119Sn-NMR spectrum shows only one signal in pH 1.2 not any longer the typical signal for dimeric MBTO (distannoxane). The single signal can be assigned to monomeric monobutylstannonic acid.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °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 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 study shows that the test material is hydrolytically stable at pH 4, 7, 9. After 5 days of hydrolysis at 50°C less than 10% of the test material was hydrolysed (half life at 25°C > 1 year).

Under simulated gastric conditions (0.1 M HCl /pH 1.2 /40°C/ 4 h) the 119Sn-NMR spectrum shows only one signal in pH 1.2 not any longer the typical signal for dimeric MBTO (distannoxane). The single signal can be assigned to monomeric monobutylstannonic acid.