Magnesium octadecylbenzenesulphonate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

01 July 2014-07 October 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

(2008)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Version / remarks:

(2004)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.2120 (Hydrolysis of Parent and Degradates as a Function of pH at 25°C)

Version / remarks:

(2008)

Deviations:

no

GLP compliance:

yes

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

Samples for analysis were taken immediately after preparation (t=0), after 2.4 hours and after 5 days. The samples taken at t=2.4h and at t=5 days were cooled to room temperature using running tap water.

Buffers:

- Acetate buffer pH 4, 0.01 M: aqueous solution of 16.7% 0.01 M sodium acetate and 83.3% 0.01 M acetic acid.
- Phosphate buffer pH 7, 0.01 M: aqueous solution of 0.01 M potassium di-hydrogenphosphate adjusted to pH 7 using 1 N sodium hydroxide.
- Borate buffer pH 9, 0.01 M: aqueous solution of 0.01 M boric acid and 0.01 M potassium chloride adjusted to pH 9 using 1 N sodium hydroxide.
- The buffers contain 0.0009% (w/v) sodium azide.

Details on test conditions:

- Tier 1 (preliminary) test was performed at pH 4, 7 and 9 at 49.9 ± 0.1°C and the target initial concentration was 10 µg/L.
- The buffer solutions were filter-sterilised through a 0.2 µm filter and transferred into sterile vessels.
- To exclude oxygen, nitrogen gas was purged through the solution for 5 minutes.
- Spiking solution: 100 mg/L of test substance in tetrahydrofuran.
- Test substance was spiked to the test solutions to obtain the target concentration. Spiking volume: 10 µL.
- The spiking volume was < 1% of the sample volume. Nominal concentrations were not corrected for the spiking volume.
- For each sampling time, duplicate sterile vessels under vacuum were filled with 6 mL test solution and placed in the dark in a temperature controlled environment.
- The pH of the test solutions was determined at each sampling time. Actual pH : 4.1, 7.1 and 9.0.
- Blank buffer solutions containing a similar content of blank spiking solution were treated similarly as the test samples and analysed at t=0. No test substance was detected in the blank buffer solutions.

Duration:

5 d

pH:

4.1

Temp.:

50 °C

Initial conc. measured:

8.01 - 8.86 µg/L

Duration:

5 d

pH:

7.1

Temp.:

50 °C

Initial conc. measured:

9.51 - 9.79 µg/L

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

9.47 - 9.8 µg/L

Number of replicates:

Two

Positive controls:

no

Negative controls:

no

Preliminary study:

At pH 4, 7 and pH 9, a significant decrease in concentration during the test period was measured (see table below).

Test performance:

RECOVERIES
- The recovery in the table below is the mean of duplicate test samples.
- Recovery is the concentration analysed for the test sample at t=0 relative to the nominal concentration.
- The mean recoveries at pH 4, pH 7 and pH 9 fell within the acceptable range of 70-110%.

Transformation products:

not measured

% Recovery:

84

pH:

4

Temp.:

50 °C

% Recovery:

97

pH:

7

Temp.:

50 °C

% Recovery:

96

pH:

9

Temp.:

50 °C

Key result

pH:

4

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

7

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

9

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Tier 1 results of the substance at pH 4, pH 7 and pH 9 at 49.9 ±1 °C

 

pH code	Sampling time	Analysed concentration [µg/L]	Degree of hydrolysis relative to t=0 [%]		Absolute difference [%] 2.4 hours versus 5 days	Actual pH
			Individual	Mean
pH 4	0 hours	8.01/8.86				4.1/4.1
	2.4 hours	2.03/1.92	76/77	77		4.1/4.1
	5 days	1.48/1.21	82/86	84	7.4	4.1/4.1
pH 7	0 hours	9.51/9.79				7.1/7.1
	2.4 hours	2.68/3.62	72/62	67		7.1/7.1
	5 days	2.01/1.50	79/84	82	14	7.1/7.1
pH 9	0 hours	9.47/9.80				9.0/9.0
	2.4 hours	4.14/4.01	57/58	58		9.0/9.0
	5 days	2.03/7.92^1	79	79	21	9.0/9.0

 ¹          Outlier; not used for calculations.

Validity criteria fulfilled:

yes

Conclusions:

Based on the Tier 1 results and the low water solubility of the substance, it was concluded that it is technically not possible to perform the hydrolysis study for this substance. Due to the absence of hydrolysable groups it could be concluded that hydrolysis is not likely for the substance.

Executive summary:

The preliminary (Tier 1) test of the hydrolysis study as outlined in EC C.7, OECD 111 and OPPTS 835.2120 guidelines was performed at pH 4, 7 and 9 and at 50°C (GLP-compliant study). A significant decrease in concentration ( = 79%) was measured after the 5 -day test period. However, non-linear relationships were obtained indicating that hydrolysis - if any - is not the only process causing the concentration decrease. The substance does not contain hydrolysable functional groups. It was therefore assumed that absorption and/or precipitation are significantly contributing to the observed concentration decrease. Testing at higher concentrations (to lower the influence of adsorption) is not possible due to the limited solubility of the substance in aqueous solutions. Testing at lower concentration (to prevent possible precipitation) is not possible either because it will not be possible to measure such a low concentrations (the limit of quantification of the analytical method is 1 µg/L).

Description of key information

As per the conclusions in the source study, the magnesium alkylbenzene sulphonate does not have any hydrolysable functional groups. The registration substance differs only in the length of the alkyl chain, therefore it can be conlcuded that it doesn't contain any hyrdolysable functional groups.