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Environmental fate & pathways

Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
migrated information: read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
23 November 2010-27 January 2011
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Performance:
The rate of hydrolysis of the test substance as a function of pH was determined at pH values normally found in the environment (pH 4-9).

Preliminary test - Tier 1:
The buffer solutions were filter-sterilised through a 0.2 µm FP 30/0.2 CA-S filter (Whatman, Dassel, Germany) and transferred into a sterile vessel. To exclude oxygen, nitrogen gas was purged through the solution for 5 minutes. The test substance was spiked to the solutions at a target concentration of 25 mg/l using a spiking solution in 70/30 (v/v) acetonitrile/water. 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 at 50.0°C +/- 0.1°C.

Note: the spiking volume was < 1% of the sample volume. Nominal concentrations were not corrected for the spiking volume.

The concentration of the test substance in the test samples was determined immediately after preparation (t=0) and after 5 days. The samples taken at t=5 days were cooled to room temperature using running tap water. The samples were diluted in a 1:1 (v:v) ratio with acetonitrile and analysed. Blank buffer solutions containing 70/30 (v/v) acetonitrile/water were treated similarly as the test samples and analysed at t=0. The pH of each of the test solutions (except for the blanks) was determined at each sampling time.
Buffers:
Acetate buffer pH 4, 0.1 M: solution of 16.6% 0.1 M sodium acetate and 83.4% 0.1 M acetic acid. The buffer contains 0.0009% (w/v) sodium azide.

Phosphate buffer pH 7, 0.1 M: solution of 0.1 M potassium dihydrogenphosphate adjusted to pH 7 using 10 N sodium hydroxide. The buffer contains 0.0009% (w/v) sodium azide.

Borate buffer pH 9, 0.1 M: solution of 0.1 M boric acid and 0.1 M potassium chloride adjusted to pH 9 using 10 N sodium hydroxide. The buffer contains 0.0009% (w/v) sodium azide.

Duration:
5 d
pH:
4
Temp.:
50 °C
Initial conc. measured:
ca. 25 mg/L
Duration:
5 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
ca. 25 mg/L
Duration:
5 d
Temp.:
50 °C
Initial conc. measured:
ca. 25 mg/L
Preliminary study:
At pH 4, pH 7 and pH 9 a degree of hydrolysis of < 10% was observed after 5 days. It demonstrated that the half-life time of the test substance at 25°C is > 1 year. According to the guideline, no further tests were required.

No test substance was detected in the blank buffer solutions.

The mean recoveries of the buffer solutions fell within the criterion range of 90-110%. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test substance.
Transformation products:
not measured
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
25 °C
DT50:
> 1 yr
Type:
(pseudo-)first order (= half-life)
Validity criteria fulfilled:
yes
Conclusions:
The preliminary test (Tier 1) was performed for the determination of the rate of hydrolysis of LIN10001:4,4’-Isopropylidenediphenol, propoxylated at pH values normally found in the environment (pH 4-9).

At each pH value a degree of hydrolysis of < 10% was observed after 5 days. According to the guideline, performance of the main study (Tier 2) was not required.

The half-life time of the test substance at 25°C was > 1 year at pH4, pH7 and pH9.


Description of key information

The test substance was considered as hydrolytically stable and no advanced test was required. The results of testing on BPA 2PO can be used to predict that the BPA 3PO will also be hydrolytically stable based on the higher degree of propoxylation.

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
25 °C

Additional information

The hydrolysis half-life of BPA 2PO was determined in accordance with the OECD Guideline for Testing of Chemicals 111 and GLP requirements. During the preliminary test performed at 50°C for 5 days, the substance has been found to be hydrolytically stable at all the tested pHs. Indeed, the results showed that the hydrolysis percentages of samples were less than 10% after 5 days. Therefore, the test substance was considered as hydrolytically stable and no advanced test was required. This study can be used as a read-across for BPA 3PO. Indeed, as BPA 2PO has been found to be stable, BPA 3PO which presents a highest level of propoxylation compared to BPA 2PO can be considered as again more stable.