1-methoxy-4-[3-methyl-4-(2-phenylethoxy)but-3-en-1-yl]benzene

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

03-09-2021 to 12-11-2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Guideline study performed under GLP. All relevant validity criteria were met.

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

Principles of method if other than guideline:

The test followed a method in accordance with OECD TG 111 (hydrolysis as a function of pH) and/or EU Method C.7 - as a screening study (tier 1) for the hydrolysis properties of the test substance and/or determination of hydrolysis rate constants (tier 2). Specific identification of hydrolysis products (tier 3) was performed.

GLP compliance:

yes (incl. QA statement)

Remarks:

inspected: November 2019 ; signature: August 2020

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products: Duplicate vessels were performed per pH and sampling date, by single injection analysis.
Preliminary test (tier 1): all pH : 0 hours and 120 hours (as appropriate depending on results) with further timepoints, as applicable.
Definitive test (tier 2 and tier 3): The definitive test was conducted for at least two half-live periods, optimally until 90 % degradation (if possible) is reached or 30 days, whichever is shorter. Samples were taken at test start (0 h) and at a minimum of 9 spaced points, at each test temperature (between 10% and 90% hydrolysis). All test item containing samples were stabilized immediately by liquid-liquid extraction (if possible, less than 30 min until start of analyses, but at least not more than 2.5% of the total study time) and analysed.
- Sampling method: After sampling, all samples were first spiked with 100 μL of 1-phenylethanol (2.5 mg/L). Then 5 mL cyclohexane (enrichment factor 2) and afterwards 1 g sodium chloride were added, the vessels closed and extracted by shaking with hand for 2 minutes. After extraction the cyclohexane was dried with sodium sulphate.
0.5 mL of the dried extract was filled into a HPLC vial, 0.5 mL cyclohexane and 50 μL of hexachlorobenzene (2 mg/L) were added and analysed (dilution factor 2). The samples of the final samplings were measured undiluted (1 mL sample + 50 μL of hexachlorobenzene (2 mg/L)), if necessary. Within the definitive test, all test item containing samples were extracted immediately with cyclohexane (if possible, less than 30 min until start of analyses, but at least not more than 2.5% of the total study time). All the test samples were stabilized via liquid extraction. Stability of prepared samples was 8 days for parent compound and 3 days for 2-Phenylethanol transformation product (documented in the full study report).
- Sampling methods for the volatile compounds, if any: See above. GC-MS/MS was performed.
- Sampling intervals/times for pH measurements: Start prior to test item application at 20°C, 30°C and 50°C
- Sampling intervals/times for sterility check: In the definitive test : as transformation occurs the sterility of the test solutions was checked at the end of the test by colony forming units (CFU)-determination with Water Plate Count Agar from additional sample. By incubation at 36 ± 1 °C for 48 ± 4 h and at 22 ± 1 °C for 72 ± 4 h. Prior to the study: buffer solutions were purged/degassed with nitrogen for 5 minutes and then the pH was checked to a precision of at least 0.1 at the test temperatures. Buffers were sterilized by filtration through 0.2 µm. Thereby ensuring sterility of the test system.
- Sample storage conditions before analysis: On the autosampler prior to analysis.
- Other observation, if any (e.g.: precipitation, color change etc.): None reported.

Buffers:

- pH: Sterile buffer solutions with pH values : pH 4, pH 7 and pH 9
- Type and final molarity of buffer: See below, in accordance with the OECD TG 111 guideline.
- Composition of buffer: Buffer solutions were prepared from chemicals with analytical grade or better quality following the composition guidance given in KÜSTER-THIEL, Rechentafeln für die Chemische Analytik (edition not specified, in German), and/or the OECD TG 111 guideline. The buffers were prepared by direct weighing of the buffer components (nominal values) as below.
• pH 4 : 0.377 g of sodium hydroxide and 11.543 g of mono potassium citrate were dissolved in 1000 mL ultrapure water.
• pH 7: 8.235 g of ammonium acetate were dissolved in 1000 mL ultrapure water.
• pH 9 : 0.868 g sodium hydroxide, 3.727 g potassium chloride and 3.092 g boric acid were dissolved in 1000 mL ultrapure water.
Prior to the study: buffer solutions were purged/degassed with nitrogen for 5 minutes and then the pH was checked to a precision of at least 0.1 at the test temperatures. Buffers were sterilized by filtration through 0.2 µm. Thereby ensuring sterility of the test system.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: (sterile) Headspace vials, volume: 20 mL ; fill volume 10 mL
- Sterilisation method: Prior to the study: buffer solutions were purged/degassed with nitrogen for 5 minutes and then the pH was checked to a precision of at least 0.1 at the test temperatures. Buffers were sterilized by filtration through 0.2 µm. Thereby ensuring sterility of the test system.
- Lighting: Not applicable. Photolytic effects were avoided by using opaque water baths.
- Measures taken to avoid photolytic effects: All solutions shielded from light. See above.
- Measures to exclude oxygen: Buffer solutions were purged/degassed with nitrogen for 5 minutes and then the pH was checked to a precision of at least 0.1 at the test temperatures. Buffers were sterilized by filtration through 0.2 µm. Thereby ensuring sterility of the test system.
- Details on test procedure for unstable compounds: Not applicable.
- Details of traps for volatile, if any: Not applicable (closed system)
- If no traps were used, is the test system closed/open: Closed system.
- Is there any indication of the test material adsorbing to the walls of the test apparatus?: None reported. Co-solvent: 0.1% (v/v) of acetone, was utilised within the study.
TEST MEDIUM
- Volume used/treatment: See below for information on the test system. Test container: (sterile) Headspace vials, volume: 20 mL. Test volume: 10 mL (fill volume)
- Kind and purity of water: Purified water via In-house device Milli-Q Advantage A10 (≥ 18.2 MΩ/cm and ≤ 50 ppb TOC)
- Preparation of test medium: 9.9 mL of the respective buffer solution pH 4, 7 or 9 were introduced to the test vessels. 0.1 mL of the test item solution (5000 mg/L in
acetonitrile) was spiked into the vessels and the vessels were closed. For control samples, 9.9 mL of the respective buffer solution was spiked with 0.1 mL acetonitrile without test item. After the vials were sealed, they were transferred into the thermostat. The time between test item application and transfer to thermostat / analysis did not exceed 30 min. Test concentration/solution: 50 µg/L. Spiking solution: 5000 mg/L in acetonitrile.
- Renewal of test solution: Not applicable.
- Identity and concentration of co-solvent: 1% (v/v) of acetonitrile
OTHER TEST CONDITIONS
- Adjustment of pH: Not applicable.
- Dissolved oxygen: Oxygen free or minimised to extent possible. pH buffers were purged with nitrogen for 5 min and then the pH was checked to a precision of at least 0.1 at the test temperatures. Buffers were sterilized by filtration through 0.2 μm prior to introduction to sealed headspace vial test vessels.

Duration:

120 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

51.5 mg/L

Remarks:

Preliminary test (pH 4)

Duration:

120 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

54.5 mg/L

Remarks:

Preliminary test (pH 7)

Duration:

120 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

51.2 mg/L

Remarks:

Preliminary test (pH 9)

Duration:

170 h

pH:

4

Temp.:

20 °C

Initial conc. measured:

60.3 µg/L

Remarks:

Definitive test (pH 4 / 20 °C)

Duration:

696 h

pH:

7

Temp.:

20 °C

Initial conc. measured:

50.2 µg/L

Remarks:

Definitive test (pH 7 / 20 °C)

Duration:

695 h

pH:

9

Temp.:

20 °C

Initial conc. measured:

57.3 µg/L

Remarks:

Definitive test (pH 9 / 20 °C)

Duration:

99.6 h

pH:

4

Temp.:

30 °C

Initial conc. measured:

54.2 µg/L

Remarks:

Definitive test (pH 4 / 30 °C)

Duration:

696 h

pH:

7

Temp.:

30 °C

Initial conc. measured:

50.2 µg/L

Remarks:

Definitive test (pH 7 / 30 °C)

Duration:

695 h

pH:

9

Temp.:

30 °C

Initial conc. measured:

57.3 µg/L

Remarks:

Definitive test (pH 9 / 30 °C)

Duration:

26.3 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

51.7 µg/L

Remarks:

Definitive test (pH 9 / 50 °C)

Duration:

696 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

50.2 µg/L

Remarks:

Definitive test (pH 7 / 50 °C)

Duration:

695 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

57.3 µg/L

Remarks:

Definitive test (pH 9 / 50 °C)

Number of replicates:

Duplicates [per pH and sampling date] (double vessels, single injection)

Positive controls:

no

Remarks:

Reference item : test is not an OECD TG 111 guideline requirement

Negative controls:

no

Remarks:

However, for each test system, two blank samples were prepared in the same manner of the fortified samples without the spiking step and analysed

Preliminary study:

In the preliminary test (tier 1) at 50 °C: more than 10 % of the test item was degraded after 120 hours for each tested pH value (4, 7 and 9).
pH 4: 99.0% degradation at 120 hours
pH 7: 51.7% degradation at 120 hours
pH 9: 39.6% degradation at 120 hours
The extent of hydrolysis after 120 hours (5 days) indicated further testing would be required to estimate the rate constant and half life.
Estimated half-life from tier 1 was pH 4, pH 7 and pH 9 : << 1 year

Test performance:

In the definitive test: The time between sampling and analysing did not exceed 30 min, and the test samples were stabilized via liquid extraction immediately.
The temperature was outside of the target range at pH 7 and 9 at 50 °C : with a minimum temperature of 49.0 °C for 2.44% of the total run time (17 h of 696 h total run time).
Separately, the temperature of the sterility check at 36 ± 1 °C was out of the predicted temperature range with a minimum temperature of 33.8 °C for 2 h.
At four sampling points, erroneously no procedural recovery samples were prepared.
None of the above study plan deviations was considered to have impacted the quality or integrity of the study.
The definitive test was conducted with a nominal test item concentration of 50 μg/L in buffer solutions at pH 4, 7 and 9 with 1% acetonitrile as co-solvent at temperatures of 20, 30 and 50 °C, respectively. Samples were taken at test start (0 h) and at least 9 spaced points until test end. Pure test system (buffer solution at the respective pH-value with 1% acetonitrile as co-solvent) was analysed at test start and test end and there was no analytical interference with the test item. All applicable validity criteria were considered to be met. For further information on results, see tables.

Transformation products:

yes

Remarks:

Major transformation products detected using the analytical method(s) employed in the test.

No.:

#1

No.:

#2

Details on hydrolysis and appearance of transformation product(s):

- Formation and decline of each transformation product during test: The formation of 2-Phenylethanol was observed in all pH and temperature combinations. The formation and/or then decline of 2-Phenylethanol was observed at pH 4 and 50°C. Applicant assessment indicates: the formation then declines at pH 7 and/or pH 9 were less pronounced possibly due to slower parent substance hydrolysis rates than at pH 4. Within the study, it was concluded: 2-Phenylethanol was formed at each test condition and was identified as the major transformation product. Its quantification showed that after formation, this product declined with time. Additionally, the corresponding aldehyde was identified but could only be analysed qualitatively.
- Pathways for transformation: The pathway of transformation is reported in the full study report (see ‘attached background information’ for more information.

Remarks on result:

other: See tables.

Key result

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0 s-1

DT50:

2.38 d

Type:

(pseudo-)first order (= half-life)

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0 s-1

DT50:

89.4 d

Type:

(pseudo-)first order (= half-life)

Key result

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0 s-1

DT50:

44.8 d

Type:

(pseudo-)first order (= half-life)

Other kinetic parameters:

For all test conditions the (natural logarithm) ln concentration vs. time plots have regression graphs with slopes significantly non-zero. First order reaction kinetics were applied for data computation. A confirmation of pseudo first order reaction kinetics with coefficients of determination > 0.8 was achieved for most test conditions. This included pH 4 all temperatures, pH 7 at 50°C, pH 9 at 50°C. For the test conditions pH 7 at 20°C and 30°C as well as pH 9 at 20°C and 30°C no clear confirmation of pseudo first order reaction kinetics with coefficients of determination > 0.8 was achieved. Within the study, it was deemed the correlation factor was partly < 0.8 due to the slow hydrolysis rate. Nevertheless, based on the obtained data the pseudo first order reaction kinetics was deemed to be the best fit model for computation of kinetics data.

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes. (no indications in the study of any anomalies). By use of appropriate buffers however pH was not continuously monitored throughout the study, sterility was examined by colony forming units (CFU)-determination with Water Plate Count Agar from additional samples of the definitive test by incubation.
- Anomalies or problems encountered (if yes): For all test conditions the ln concentration vs. time plots have regression graphs with slopes significantly non-zero. First order reaction kinetics were applied for data computation. A confirmation of pseudo first order reaction kinetics with coefficients of determination > 0.8 was achieved for most test conditions. This included pH 4 all temperatures, pH 7 at 50°C, pH 9 at 50°C. For the test conditions pH 7 at 20°C and 30°C as well as pH 9 at 20°C and 30°C no clear confirmation of pseudo first order reaction kinetics with coefficients of determination > 0.8 was achieved. Within the study, it was deemed the correlation factor was partly < 0.8 due to the slow hydrolysis rate. Nevertheless, based on the obtained data the pseudo first order reaction kinetics was deemed to be the best fit model for computation of kinetics data.

MAJOR TRANSFORMATION PRODUCTS
Major transformation products could be detected (using the analytical method employed in the test). The formation of 2-Phenylethanol was observed in all pH and temperature combinations. The formation and/or then decline of 2-Phenylethanol was observed at pH 4 and 50°C. Applicant assessment indicates: the formation then declines at pH 7 and/or pH 9 were less pronounced possibly due to slower parent substance hydrolysis rates than at pH 4. Within the study, it was concluded: 2-Phenylethanol was formed at each test condition and was identified as the major transformation product. Its quantification showed that after formation, this product declined with time. Additionally, the corresponding aldehyde was identified but could only be analysed qualitatively.

MINOR TRANSFORMATION PRODUCTS
No other minor transformation products could be detected (using the analytical method employed in the test).

MINERALISATION (distinguish between dark and irradiated samples)
Not examined. All testing completed in the dark or protected from light.

INDICATION OF UNSTABLE TRANSFORMATION PRODUCTS:
Not examined.

VOLATILIZATION (at end of study)
Not examined.

UNIDENTIFIED RADIOACTIVITY (at end of study)
Not examined.

PATHWAYS OF HYDROLYSIS
The pathway of transformation is reported in the full study report (see ‘attached background information’ for more information.

SUPPLEMENTARY EXPERIMENT (if any): RESULTS: See information within “overall remarks, attachments” as to the modelled data from the primary hydrolysis data. Full tables of the primary data for each measured time-point, are available in the full study report..

Table 1. Reaction Rate Constants and Half-Lives with pH

pH 4
	20 °C	30 °C	50 °C
Slope of regression graph	-7.17 x10^-3	-2.06 x10^-2	-1.13 x10^-1
Correlation factor [r2]	0.920	0.980	0.925
Reaction rate constantkobs[1/s]	1.99 x10^-6	5.72 x10^-6	3.13 x10^-5
Half-life T½ [h]	96.7	33.7	6.15
Confidence interval of half-life T½ [h]	82.6 to 116	30.3 to 37.2	4.36 to 7.92
Half-life T½ [d]	4.03	1.40	0.256
Confidence interval of half-life T½ [d]	3.44 to 4.83	1.26 to 1.55	0.182 to 0.330
pH 7
	20 °C	30 °C	50 °C
Slope of regression graph	-1.76 x10^-4	-6.28 x10^-4	-2.49 x10^-3
Correlation factor [r2]	0.0981	0.624	0.975
Reaction rate constantkobs[1/s]	4.89 x10^-8	1.75 x10^-7	6.92 x10^-7
Half-life T½ [h]	3938	1103	278
Confidence interval of half-life T½ [h]	1371 to infinity	784 to 2243	251 to 308
Half-life T½ [d]	164.0	46.0	11.6
Confidence interval of half-life T½ [d]	57.1 to infinity	32.7 to 93.5	10.5 to 12.8
	pH 9
	20 °C	30 °C	50 °C
Slope of regression graph	-4.77 x10^-4	-8.61 x10^-4	-2.66 x10^-3
Correlation factor [r2]	0.637	0.760	0.986
Reaction rate constantkobs[1/s]	1.32 x10^-7	2.39 x10^-7	7.38 x10^-7
Half-life T½ [h]	1455	805	261
Confidence interval of half-life T½ [h]	1020 to 2974	627 to 1218	242 to 281
Half-life T½ [d]	60.6	33.6	10.9
Confidence interval of half-life T½ [d]	42.5 to 124.0	26.1 to 50.8	10.1 to 11.7

 

Table 3. Results of Arrhenius Calculations

pH value	[°C]	-EA/R	ln A	EA [J * mol-1]
4	20	-8656	16.4	7.20 x10^4
	30
	50
7	20	-8270	11.5	6.88 x10^4
	30
	50
9	20	-5446	2.73	4.53 x10^4
	30

Validity criteria fulfilled:

yes

Remarks:

The study meets the tier 1, tier 2 and tier 3 validity criteria.

Conclusions:

The substance was found in a tier 1 preliminary test to be unstable to hydrolysis in water at pH 4, pH 7 and pH 9 (t1/2: < 5 days) at 50 °C and therefore the equivalent half-life at 25°C: would be << 1 year. Subsequently, in a tier 2 & 3 definitive test: the substance was found to be unstable with half-lives at 25°C determined by the Arrhenius equation as follows: pH 4 : 2.38 days, pH 7: 89.4 days and pH 9: 44.8 days.

Executive summary:

The test followed a method in accordance with OECD TG 111 and EU Method C.7 (abiotic degradation: hydrolysis as a function of pH) under GLP serving as both a screening study (tier 1) and rate constant determination (tier 2) with identification and/or quantification of transformation products (tier 3), where possible: for the hydrolysis properties of the item. The study was conducted with the test vessels protected from light. Buffer solutions were prepared from chemicals with analytical grade or better quality and were purged/degassed with nitrogen for 5 minutes and then the pH was checked to a precision of at least 0.1 at the test temperatures. Buffers were sterilized by filtration through 0.2 µm. Thereby ensuring sterility of the test system. The preliminary test was conducted with a test item concentration of 50 μg/L in buffer solutions at pH 4, 7 and 9 at 50 °C with 1% acetonitrile as co-solvent. For all pH-values, the definitive test was performed, as a significant reduction (> 10%) of the test item concentration was observed. The definitive test was conducted with a nominal test item concentration of 50 μg/L in buffer solutions at pH 4, 7 and 9 with 1% acetonitrile as co-solvent at temperatures of 20, 30 and 50 °C, respectively. Samples were taken at test start (0 h) and at least 9 spaced points until test end. Pure test system (buffer solution at the respective pH-value with 1% acetonitrile as co-solvent) was analysed at test start and test end and there was no analytical interference with the test item. The test solutions were prepared at test start via spiking solution. 9.9 mL of the respective buffer solution pH 4, 7 or 9 were introduced to the test vessels. 0.1 mL of the test item solution (5000 mg/L in acetonitrile) was spiked into the vessels (headspace vials) and the vessels were closed. For control samples, 9.9 mL of the respective buffer solution was spiked with 0.1 mL acetonitrile without test item. After the (headspace vials fill volume 10 mL) vials were sealed, they were transferred into the thermostat. The time between test item application and transfer to thermostat and analysis did not exceed 30 minutes. Within the definitive test, test samples were stabilized via liquid extraction and the time between sampling and analysis did not exceed 30 minutes. 2-Phenylethanol was formed at each test condition and was identified as the major transformation product. Its quantification showed that after formation, this product declined with time. Additionally, the corresponding aldehyde was identified within the study but could only be analysed qualitatively. Reaction rate constants, half-lives and activation energies were calculated from the analysed samples based on a first order reaction kinetics model. A confirmation of pseudo first order reaction kinetics with coefficients of determination > 0.8 was achieved for most test conditions. Within the study, it was deemed the correlation factor was partly < 0.8 due to the slow hydrolysis rate. Nevertheless, based on the obtained data the pseudo first order reaction kinetics was deemed to be the best fit model for computation of kinetics data. Reaction rate constants, half-lives and activation energies were therefore calculated using information from the and analysed samples the Arrhenius equation. Based on a first order reaction kinetics, these were as follows: reaction rate constant (kobs) at 25°C [1/s]: pH 4 : 3.37 x10^-6, pH 7: 8.97 x10^-8 and pH 9: 1.79 x10^-7. The equivalent half-lives at 25°C: pH 4 : 2.38 days, pH 7: 89.4 days and pH 9: 44.8 days. Using a categorisation scheme of hydrolysis being ‘fast’ : t1/2 ≤ 2.4 hours , ‘moderate’ : 2.4 hours ≥ t1/2 and ≤ 30 days and ‘slow’ : t1/2 > 30 days, respectively. The test item showed a moderate hydrolysis rate (t1/2 ≥ 2.4 h and ≤ 30 d) for pH 4 at all test conditions and pH 7 and 9 at 50 °C. At pH 7 and 9 at 20 and 30 °C the test item showed a slow hydrolysis rate (t1/2 > 30 d).

Reference 2

Endpoint:

hydrolysis

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance is readily biodegradable

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
In accordance with REACH Regulation (EC) No. 1907/2006 Annex VIII, column 2 section 9.2.2.1 the study does not need to be conducted if the substance is readily biodegradable. The substance rapidly degrades biotically. According to ECHA Guidance on Information Requirements and Chemical Safety Assessment (Chapter R.7a: Endpoint Specific Guidance, July 2017 and Chapter R.7b: Endpoint Specific Guidance, R.7.9, June 2017) the study does not need to be conducted.

Description of key information

Hydrolysis: half-life for hydrolysis: pH 4 : 2.38 days, pH 7: 89.4 days and pH 9: 44.8 days, at 25 °C, 1 atm, OECD TG 111, 2022

Based on a first order reaction kinetics, these were as follows: reaction rate constant (kobs) at 25°C [1/s]: pH 4 : 3.37 x10^-6, pH 7: 8.97 x10^-8 and pH 9: 1.79 x10^-7

Note: substance is ‘readily biodegradable’, further testing is scientifically not necessary.

Supporting information: substance will rapidly (bio)degrade and mineralise within 28 days.

Key Data: Biodegradation: readily biodegradable, mean biodegradation 72.7% at 28-days, 10-day window met ; OECD TG 301F, 2021

Reference: Biodegradation - section.

Key value for chemical safety assessment

Half-life for hydrolysis:

89.4 d

at the temperature of:

25 °C

Additional information

Key study : OECD TG 111, 2022 : The test followed a method in accordance with OECD TG 111 and EU Method C.7 (abiotic degradation: hydrolysis as a function of pH) under GLP serving as both a screening study (tier 1) and rate constant determination (tier 2) with identification and/or quantification of transformation products (tier 3), where possible: for the hydrolysis properties of the item. The study was conducted with the test vessels protected from light. Buffer solutions were prepared from chemicals with analytical grade or better quality and were purged/degassed with nitrogen for 5 minutes and then the pH was checked to a precision of at least 0.1 at the test temperatures. Buffers were sterilized by filtration through 0.2 µm. Thereby ensuring sterility of the test system. The preliminary test was conducted with a test item concentration of 50 μg/L in buffer solutions at pH 4, 7 and 9 at 50 °C with 1% acetonitrile as co-solvent. For all pH-values, the definitive test was performed, as a significant reduction (> 10%) of the test item concentration was observed. The definitive test was conducted with a nominal test item concentration of 50 μg/L in buffer solutions at pH 4, 7 and 9 with 1% acetonitrile as co-solvent at temperatures of 20, 30 and 50 °C, respectively. Samples were taken at test start (0 h) and at least 9 spaced points until test end. Pure test system (buffer solution at the respective pH-value with 1% acetonitrile as co-solvent) was analysed at test start and test end and there was no analytical interference with the test item. The test solutions were prepared at test start via spiking solution. 9.9 mL of the respective buffer solution pH 4, 7 or 9 were introduced to the test vessels. 0.1 mL of the test item solution (5000 mg/L in acetonitrile) was spiked into the vessels (headspace vials) and the vessels were closed. For control samples, 9.9 mL of the respective buffer solution was spiked with 0.1 mL acetonitrile without test item. After the (headspace vials fill volume 10 mL) vials were sealed, they were transferred into the thermostat. The time between test item application and transfer to thermostat and analysis did not exceed 30 minutes. Within the definitive test, test samples were stabilized via liquid extraction and the time between sampling and analysis did not exceed 30 minutes. 2-Phenylethanol was formed at each test condition and was identified as the major transformation product. Its quantification showed that after formation, this product declined with time. Additionally, the corresponding aldehyde was identified within the study but could only be analysed qualitatively. Reaction rate constants, half-lives and activation energies were calculated from the analysed samples based on a first order reaction kinetics model. A confirmation of pseudo first order reaction kinetics with coefficients of determination > 0.8 was achieved for most test conditions. Within the study, it was deemed the correlation factor was partly < 0.8 due to the slow hydrolysis rate. Nevertheless, based on the obtained data the pseudo first order reaction kinetics was deemed to be the best fit model for computation of kinetics data. Reaction rate constants, half-lives and activation energies were therefore calculated using information from the and analysed samples the Arrhenius equation. Based on a first order reaction kinetics, these were as follows: reaction rate constant (kobs) at 25°C [1/s]: pH 4 : 3.37 x10^-6, pH 7: 8.97 x10^-8 and pH 9: 1.79 x10^-7. The equivalent half-lives at 25°C: pH 4 : 2.38 days, pH 7: 89.4 days and pH 9: 44.8 days. Using a categorisation scheme of hydrolysis being ‘fast’ : t1/2 ≤ 2.4 hours , ‘moderate’ : 2.4 hours ≥ t1/2 and ≤ 30 days and ‘slow’ : t1/2 > 30 days, respectively. The test item showed a moderate hydrolysis rate (t1/2 ≥ 2.4 h and ≤ 30 d) for pH 4 at all test conditions and pH 7 and 9 at 50 °C. At pH 7 and 9 at 20 and 30 °C the test item showed a slow hydrolysis rate (t1/2 > 30 d).

References:

1. OECD TG 111 - hydrolysis as a function of pH, (2004)

2. ECHA Guidance on Information Requirements and Chemical Safety Assessment (Chapter R.7b: Endpoint Specific Guidance, R.7.9, v4.0, June 2017)

In accordance with REACH Regulation (EC) No. 1907/2006 Annex VIII, column 2 section 9.2.2.1 the study does not need to be conducted if the substance is readily biodegradable. The substance rapidly degrades biotically. According to ECHA Guidance on Information Requirements and Chemical Safety Assessment (Chapter R.7a: Endpoint Specific Guidance, July 2017 and Chapter R.7b: Endpoint Specific Guidance, R.7.9, June 2017) the study does not need to be conducted.