Registration Dossier

Data platform availability banner - registered substances factsheets

Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Environmental fate & pathways

Hydrolysis

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
24 June 2014 to 12 September 2014
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
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Batch: PE00083052
Purity: 96.3% (sum of the two isomers)
Analytical monitoring:
yes
Preliminary study:
A preliminary test (tier 1) was carried out at 50 °C. A degree of hydrolysis of < 10% was observed at pH 7 and at pH 9 after 5 days, equivalent to a half-life greater than 1 year at 25 °C is > 1 year. According to the guidelines, no further tests were required at these two pH values. In contrast, the degree of hydrolysis observed in the preliminary test at pH4 was ≥ 10%. The % of inital concentration was approximately 50% after 2 hours, 22% after 4 hours with no test substance detected after 24 hours. Therefore higher tier (tier 2) hydrolysis tests were performed at three temperatures (40, 50 and 60 °C).
Transformation products:
not measured
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
0 s-1
DT50:
14.7 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
pH:
9
Temp.:
25 °C
DT50:
> 1 yr

Results

In the preliminary test, for pH 4, the extent of hydrolysis after 120 hours indicated that a further test (Tier 2), conducted at 40.0, 50.0 and 60.0 °C, was required to estimate the rate constant and half-life.

At pH 7 and pH 9, less than 10% hydrolysis after 5 days at 50 °C, equivalent to a half-life greater than 1 year at 25°C.

 

pH 4 Tier 2

The Arrhenius plot was constructed using the data shown in the following table:

T (°C)

T (k)

1/T(K)

Kobs(hr-1)

Ln Kobs

40

313.15

3.19 x 10-3

0.143

-1.95

50

323.15

3.10 x 10-3

0.294

-1.23

60

333.15

3.00 x 10-3

0.543

-0.611

From the graph of the above data, the rate constant and half-life at 25 °C have been estimated to be as follows:

kobs= 4.71 x 10-2hour-1

= 1.31 x 10-5second-1

T½= 14.7 hours

 

(see attachment for graphs and tables)

 

Validation

The linearity of the detector response with respect to concentration was assessed over the nominal concentration range of 1 to 10 mg/L for all three solution matrices. This was satisfactory with coefficient of determination values of 0.9997, 0.9991 and 0.9987 being obtained for pH 4, pH 7 and pH 9 respectively.

The correlation coefficient r2of the calibration curve was greater than 0.99 (optimum 1.0000).

This reflects the linearity of the GC-system within the nominal calibration range of 1 mg/L to 10 mg/L of the test item.

Discussion

The kinetics of the study have been determined to be consistent with that of a pseudo-first order reaction as the graphs of log10 concentration versus time are straight lines.

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

It has been observed that the rate of hydrolysis increases with a decrease in pH.

The buffer solutions at pH 7 and pH 9 were boiled, glass vessels were used with limited head space above the sample volume and a nitrogen headspace was introduced at the beginning of the sampling. The reason for this additional change in buffers and glass vessels was that preliminary testing at all pH’s produced non-pseudo first order results, therefore additional precautions were taken to limit the amount of reaction with air and volatilization of the test mixture.

The rate constant and estimated half-life at 25 °C of the test item are shown in the following table:

pH

Rate constant (s-1)

Estimated half-life at 25°C

4

1.31x10-5

14.7 hours

7

-

> 1 year

9

-

> 1 Year

Validity criteria fulfilled:
yes
Conclusions:
The rate constant and estimated half-life at 25 °C of the test item are shown below:
pH 4: T½ @ 25°C - 14.7 hours, Rate constant - 1.31x10-5 s-1
pH 7: T½ @ 25°C - > 1 year
pH 9: T½ @ 25°C - > 1 year
Executive summary:

The hydrolytic stability of Stemone, as a function of pH, has been evaluated using a procedure designed to be compatible with Method C7 Abiotic Degradation, Hydrolysis as a Function of pH of Commission Regulation (EC) No 440/2008 of 30 May 2012 and Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004. The results are as follows:

pH Rate constant (s-1) Estimated half-life at 25°C
4 1.31x10-5 14.7 hours
7 - > 1 year
9 - > 1 Year

Description of key information

The test item was found to be hydrolytically unstable at pH 4 (t1/2 = 14.7 hours at 25 °C) but hydrolytically stable at pH 7 and 9. The worst-case half-life of > 1 year at pH 7 and pH 9 has been used as the key value for chemical safety assessment.

Key value for chemical safety assessment

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

Additional information

The hydrolytic stability of Stemone, as a function of pH, has been evaluated using a procedure designed to be compatible with Method C7 Abiotic Degradation, Hydrolysis as a Function of pH of Commission Regulation (EC) No 440/2008 (as amended) of 30 May 2008 and Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004. The rate of hydrolysis of the test substance was determined at pH values normally found in the environment (pH 4-9).

A preliminary test (tier 1) was carried out at 50 °C. A degree of hydrolysis of < 10% was observed at pH 7 and at pH 9 after 5 days, equivalent to a half-life greater than 1 year at 25 °C. According to the guidelines, no further tests were required at these two pH values. In contrast, the degree of hydrolysis observed in the preliminary tests at pH4 was ≥ 10%. The % of inital concentration was approximately 50% after 2 hours, 22% after 4 hours and no test substance detected after 24 hours. Therefore higher tier (tier 2) hydrolysis tests were performed at three temperatures (40, 50 and 60 °C). The rate constant and half-life time of the test item at each temperature was obtained and the Arrhenius equation was used to determine the rate constant and half-life time at 25°C. The latter was calculated to be 14.7 hours.

Research to investigate the identity or nature of the hydrolysis products and the rates of their formation and decline was not performed. However, based on the chemical structure of the test item, acid catalysed hydrolysis of the oxime function most likely occurs to give the corresponding ketone (5-methylheptan-3-one, CAS 541 -85 -5, estimated log Kow of 2.147 using Kowwin v1.68, readily biodegradable according to respective REACH dossier).

The revised ECHA guidance (Chapter R.7b, version 4.0, June 2017) states that “For the PBT/vPvB assessment purposes, the testing temperature of 12°C is required for tier 2 testing purposes”. The ECHA rationale is “that 12°C is at present considered by authorities as the mean temperature of European surface waters and is required by the ECHA Member State Committee to be used as the testing temperature for new simulation degradation tests”. The OECD 111 guideline (adopted 13 April 2004) on hydrolysis suggests a temperature range of 10-70°C (preferably with at least one temperature below 25 °C utilised) since this encompasses the reporting temperature of 25 °C and most of the temperatures accounted in the field. In the study performed on Stemone (study period Jun-Sept 2014), the lowest temperature employed was 40 °C. ECHA proposes that “a rough hydrolysis temperature correction estimate may be done by using the following equation: t ½ (X°C) = t ½ e (0.08 (T - X).” Applying this approximation to the experimentally determined half-life results for Stemone gives an estimated half-life of 46-60 hours (pH 4) at 12 °C – see Table below.

 

pH

Temperature [°C]

t½ Corrected to 12 °C

Unit

4

40

4.85

45.6

hours

4

50

2.36

49.3

hours

4

60

1.28

59.6

hours

 

There is currently no cut off for hydrolysis rate, which could alone be used as justification to conclude that a substance is not persistent and, according to ECHA guidance R11, the degradation half-lives obtained in a hydrolysis test cannot be compared to the persistency criteria of Annex XIII (degradation half-life in freshwater > 40 days (P), > 60 days (vP)). Furthermore, rapid hydrolysis needs to be shown at all environmentally relevant pH. Based on the data above, Stemone undergoes moderate hydrolysis at pH 4 (T/12 = 14.7h at 25°C; = 46-60 h corrected to 12°C) but is not rapidly hydrolysed at pH 7 or pH 9.