1,3,2-dioxathiolane 2,2-dioxide

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Experimental starting date: 17 April 2018; Experimental completion date: 02 July 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

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)

Specific details on test material used for the study:

Identification: ESA (1,3,2-Dioxathiolane, 2,2-dioxide)
Appearance/Physical state: White solid
CAS Number: 1072-53-3
Batch Number: ESA-170926-160
Purity: 100.0%
Expiry date: 25 June 2018
Storage conditions: Approximately -20 °C, in the dark

Radiolabelling:

no

Analytical monitoring:

yes

Remarks:

(GC)

Buffers:

The test system consisted of buffered solutions at pH's 4, 7 and 9, detailed below:

Buffer solution (pH 4):
Compnents:-
Citric acid (0.006 mol dm-3)
Sodium chloride (0.004 dm-3)
Sodium hydroxide (0.007 mol dm-3)

Buffer (pH 7):
Components:-
Disodium hydrogen orthophosphate (anhydrous) (0.003 mol dm-3)
Potassium dihydrogen orthophosphate (0.002 mol dm-3)
Sodium chloride (0.002 mol dm-3)

Buffer (pH 9)
Components:-
Disodium tetraborate (0.001 mol dm-3)
Sodium chloride (0.002 mol dm-3)

The buffer solutions were passed through a 0.2 µm membrane filter to sterilize and subjected to ultrasonication and degassing with nitrogen to minimize dissolved oxygen.

Details on test conditions:

Preparation of the Test Solutions:
During method development, it was noted that the test item degraded rapidly at room temperature at pH 4, 7 and 9. Therefore, it was decided to go straight to Tier 2 testing.

Stock solutions of test item were prepared at a nominal concentration of 1.0 x 10^3 mg/L in the three buffer solutions; a 1% co-solvent of acetonitrile was used to aid solubility. The stock solutions were prepared in glass vessels, and injected immediately in a sequence of 5 injections. The standard, blank and sample vials were maintained at each test temperature.

Tier 2 testing was performed at pH 4, pH 7 and pH 9, with the standard, blank and sample solutions being maintained at 25 ± 0.5 °C and 5 ± 0.5 °C.

Tier 3:
Identification of the hydrolysis product was performed. A solution of test item at ~ 1 g/L test item in water was prepared, and then left at room temperature for at least 30 mins to hydrolyse fully. The solution was then analysed using LC-MS, in both negative and positive modes, specifically looking for the proposed hydrolysis product, Hydroxyethyl sulphate.

pH:

4

Temp.:

25 °C

pH:

4

Temp.:

5 °C

pH:

7

Temp.:

25 °C

pH:

7

Temp.:

5 °C

pH:

9

Temp.:

25 °C

pH:

9

Temp.:

5 °C

Number of replicates:

5 injections

Positive controls:

no

Negative controls:

no

Test performance:

Validation:
The linearity of the detector response with respect to concentration was assessed over the nominal concentration range of 100 to 2.0 x 103 mg/L. The results were satisfactory with a correlation coefficient (r) of 0.9998 being obtained.

Transformation products:

yes

No.:

#1

pH:

4

Temp.:

25 °C

DT50:

< 2 min

pH:

7

Temp.:

25 °C

DT50:

< 2 min

pH:

9

Temp.:

25 °C

DT50:

< 2 min

Details on results:

Typical chromatography is presented in attached background material.

For each of the pH 4, 25 °C; pH 7, 25 °C; pH 9, 25 °C; pH 4, 5 °C, pH 7, 5 °C and pH 9, 5 °C sequence runs, test item was detected in the standard solutions. However, no test item was detected in any of the sample solutions (and the standard blank and sample blank solutions).

As such, due to the delay in pressing “Start” and the sample solution being injected onto the GC injection port, the half-life of the test item in all of the pH 4, 7 and 9, at 25 and 5 °C, sample solutions was considered to be less than 2 mins.

At the end of the every analysis, the pH of the “hydrolyzed” sample solution was determined. In all of the samples, the pH of the solution had decreased to pH 2 from 3. This is consistent with the proposed hydrolysis product, Hydroxyethyl sulphate, which has a single, free sulphuric acid proton.

Tier 3 - Identification of Hydrolysis Products:
As the test item is a cyclic organo-sulphate acid ester, the hydrolysis product was proposed to be Hydroxyethyl sulphate [Molecular weight: 142.1; Smiles: OCCOS(=O)(=O)O]. See structure of hydroxethyl sulphate in illustration section.

Analysis of a hydrolyzed test solution using LC-MS showed the presence of a negative ion at m/z: 141, which would confirm the expected hydrolysis product indicated above, as [M – H] -.

Discussion:

As the test item degraded so rapidly during testing, the kinetics of the study could not be determined.

No significant peaks were observed at the approximate retention time of the test item on analysis of any matrix blank solutions.

Validity criteria fulfilled:

yes

Conclusions:

The estimated half-life at 25°C of the test item at pH 4, 7 and 9 is <2 mins.

Executive summary:

The hydrolysis behaviour of ESA (1,3,2-Dioxathiolane, 2,2-dioxide) as a function of pH has been determined.

Assessment of hydrolytic stability was carried out using a procedure designed to be compatible with Method C.7 Abiotic Degradation, Hydrolysis as a Function of pH of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004. The results are as follows:

pH	Rate constant (Hr^-1)	Estimated half-life at 25°C
4	-	< 2 mins
7	-	< 2 mins
9	-	< 2 mins

Description of key information

The hydrolysis behaviour of ESA (1,3,2-Dioxathiolane, 2,2-dioxide) as a function of pH has been determined.

pH	Rate constant (Hr^-1)	Estimated half-life at 25°C
4	-	< 2 mins
7	-	< 2 mins
9	-	< 2 mins

Key value for chemical safety assessment

Half-life for hydrolysis:

2 min

at the temperature of:

25 °C

Additional information

As the test item is a cyclic organo-sulphate acid ester, the hydrolysis product was proposed to be Hydroxyethyl sulphate [Molecular weight: 142.1; Smiles: OCCOS(=O)(=O)O].

Analysis of a hydrolyzed test solution using LC-MS showed the presence of a negative ion at m/z: 141, which would confirm the expected hydrolysis product indicated above,  as [M – H] -.