Octahydro-2H-1-benzopyran-2-one

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 08 July 2016 to 10 February 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to other study

Remarks:

validated analytical method used for quantification of the aqueous samples

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

Analytical monitoring:

yes

Remarks:

UPLC-MS

Details on sampling:

PREPARATION OF THE SAMPLES
- The buffer solutions were filter-sterilised through a 0.2 µm FP 30/0.2 CA-S filter (Whatman) and transferred into sterile vessels.
- To exclude oxygen, nitrogen gas was purged through the solutions for 5 minutes.
- The substance was spiked to the buffer solutions at a target concentration of 100 mg/L using a spiking solution in acetonitrile (10 g/L).
- Nominal concentrations were not corrected for the spiking volume (spiking volume was 1% of sample volume).
- For each sampling time, duplicate vessels under vacuum were filled with 6 mL test solution and placed in the dark in a temperature controlled environment.
- Blank buffer solutions containing a similar content of blank spiking solution (acetonitrile) were treated similarly as the test samples.

SAMPLING DETAILS
- Samples for analysis were taken immediately after preparation (t=0) and after 5 days (Tier 1) or after several sampling points after t=0 (Tier 2).
- Samples taken from solutions with a temperature > 20°C were cooled to room temperature using running tap water.

pH
The pH of the test solutions (except for the blanks) was determined at each sampling point.

Buffers:

Buffer pH 4: aqueous solution of 16.7% 0.01 M sodium acetate and 83.3% 0.01 M acetic acid.
Buffer pH 7: aqueous solution of 0.01 M potassium di-hydrogenphosphate adjusted to pH 7 using 1 N sodium hydroxide.
Buffer pH 9: aqueous solution of 0.01 M boric acid and 0.01 M potassium chloride adjusted to pH 9 using 1 N sodium hydroxide.

Remarks:
- Type of water: tap water purified by a purification system
- Each buffer contains 0.0009% (w/v) sodium azide.

Details on test conditions:

Actual pH and temperatures:

TIER 1
pH: 4.0 - 4.1. Temp.: 50°C ± 0.1°C
pH: 7.0. Temp.: 50°C ± 0.1°C
pH: 9.0. Temp.: 50°C ± 0.1°C

TIER 2
pH: 4.0 - 4.1. Temp.: 19.8°C ± 0.4°C, 50.2°C ± 0.1°C and 59.0°C ± 1.2°C
pH: 6.9 - 7.1. Temp.: 19.8°C ± 0.4°C, 50.2°C ± 0.1°C and 59.0°C ± 1.2°C
pH: 8.9- 9.0. Temp.: 19.8°C ± 0.2°C, 30.1°C ± 0.0°C and 50.0°C ± 0.3°C

During the Tier 2 study at 20°C, samples of the test at pH 4 were not protected from light during the first nine days of the test. For the test at pH 7, this was during the first eight days of the test and for the test at pH 9 during the first hours of the test. The tests at 20°C were performed in a climate room under yellow light. Plots of the logarithm of the relative concentration as a function of time however were comparable at the three temperatures tested. This shows that there has not been any photodegradation at pH 4, pH 7 and pH 9 and that the degradation observed is due to hydrolysis.

Duration:

739.12 h

pH:

4

Temp.:

20 °C

Initial conc. measured:

ca. 116 - ca. 116 mg/L

Remarks:

duplicate samples

Duration:

169.42 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

ca. 103 - ca. 115 mg/L

Remarks:

duplicate samples

Duration:

169.07 h

pH:

4

Temp.:

60 °C

Initial conc. measured:

ca. 112 - ca. 115 mg/L

Remarks:

duplicate samples

Duration:

739.77 h

pH:

7

Temp.:

20 °C

Initial conc. measured:

ca. 101 - ca. 108 mg/L

Remarks:

duplicate samples

Duration:

146.43 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

ca. 111 - ca. 113 mg/L

Remarks:

duplicate samples

Duration:

124.15 h

pH:

7

Temp.:

60 °C

Initial conc. measured:

ca. 109 - ca. 109 mg/L

Remarks:

duplicate samples

Duration:

47.65 h

pH:

9

Temp.:

20 °C

Initial conc. measured:

ca. 118 - ca. 120 mg/L

Remarks:

duplicate samples

Duration:

24 h

pH:

9

Temp.:

30 °C

Initial conc. measured:

ca. 119 - ca. 121 mg/L

Remarks:

duplicate samples

Duration:

3.5 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

ca. 124 - ca. 128 mg/L

Remarks:

duplicate samples

Number of replicates:

Two

Positive controls:

no

Negative controls:

no

Preliminary study:

At pH 4, pH 7 and pH 9, a degree of hydrolysis of ≥ 10% was observed after 5 days at 50°C (for both isomers). According to the guideline, the higher Tier test was required to determine the half-life time of the substance.

Test performance:

RECOVERIES (TIER 2)
- Recovery is the concentration analysed at t=0 (see table 'Duration of test') relative to the nominal concentration.
- The mean recovery was calculated from duplicate samples.
- The mean recoveries at each pH and temperature are shown below.
- The concentrations analysed in the test samples were not corrected for recovery.

The criterion that mean recovery should be in the range of 70-110% was not always met (see table 'Total recovery of test substance'). Because hydrolysis is calculated using the relative concentration, it was assumed that this had no effect on the outcome of the study.

Transformation products:

not specified

% Recovery:

116

pH:

4

Temp.:

20 °C

% Recovery:

109

pH:

4

Temp.:

50 °C

% Recovery:

113

pH:

4

Temp.:

60 °C

% Recovery:

104

pH:

7

Temp.:

20 °C

% Recovery:

112

pH:

7

Temp.:

50 °C

% Recovery:

109

pH:

7

Temp.:

60 °C

% Recovery:

119

pH:

9

Temp.:

20 °C

% Recovery:

120

pH:

9

Temp.:

30 °C

% Recovery:

126

pH:

9

Temp.:

50 °C

pH:

7

Temp.:

20 °C

Hydrolysis rate constant:

0.001 h-1

DT50:

652 h

Type:

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

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

0.017 h-1

DT50:

42 h

Type:

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

pH:

7

Temp.:

60 °C

Hydrolysis rate constant:

0.041 h-1

DT50:

17 h

Type:

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

pH:

9

Temp.:

20 °C

Hydrolysis rate constant:

0.052 h-1

DT50:

13 h

Type:

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

pH:

9

Temp.:

30 °C

Hydrolysis rate constant:

0.127 h-1

DT50:

5.5 h

Type:

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

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

0.766 h-1

DT50:

0.91 h

Type:

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

Key result

pH:

4

Temp.:

25 °C

DT50:

> 1 yr

Type:

not specified

Remarks on result:

other: At pH 4 and 50°C, a degree of hydrolysis of < 10% was observed between t=42.68 hours and t=169.42 hours (a period > 120 hours) in the Tier 2 study. Conclusion: half-life time at 25°C and pH 4 is > 1 year.

Key result

pH:

7

Temp.:

25 °C

DT50:

17 d

Type:

other: Arrhenius equation

Key result

pH:

9

Temp.:

25 °C

DT50:

8.4 h

Type:

other: Arrhenius equation

Details on results:

No substance was detected in the blank buffer solutions.

Validity criteria fulfilled:

yes

Conclusions:

The half-life time of the substance at 25°C and pH 4, pH 7 and pH 9 was determined to be > 1 year, 17 days and 8.4 hours, respectively.

Executive summary:

The rate of hydrolysis of the substance at pH values normally found in the environment (pH 4-9) was determined in a GLP-compliant study according to EC C.7, OECD 111 and EPA OPPTS 835.2120. A degree of hydrolysis of > 10% was determined at pH 4, pH 7 and pH 9 after 5 days and 50°C (Tier 1). Hydrolysis rates at 20, 50 and 60°C (pH 4 and pH 7) and at 20, 30 and 50°C (pH 9) were determined in a Tier 2 study.

The substance is a mixture of two isomers (cis- and trans-). In the preliminary test, the hydrolysis rate of the cis-isomer was observed to be lower than the rate of the trans isomer. During the Tier 2 study, concentration was only based on the response of the cis isomer as it was assumed that this gives a conservative value for the half-life times. The substance is anticipated to be hydrolysed in the lactone ring forming monocyclic secondary alcohol and an acid. At pH 4 no (pseudo-) first order behaviour was observed. After an initial period the substance concentration became stable.At 50°C, a degree of hydrolysis of < 10% was observed between t=42.68 h and t=169.42 h (a period > 120 hours). From this it was concluded that thehalf-life time at 25°C and pH 4 is > 1 year. At pH 7 and pH 9 the substance was shown to degrade by a pseudo-first order behaviour. Half-life times at 25°C were determined from the Arrhenius equation: 17 days at pH 7 and 8.4 hours at pH 9.

Description of key information

The rate of hydrolysis of the substance at pH values normally found in the environment (pH 4-9) was determined in a GLP-compliant study according to EC C.7, OECD 111 and EPA OPPTS 835.2120.A degree of hydrolysis of > 10% was determined at pH 4, pH 7 and pH 9 after 5 days and 50°C (Tier 1). Hydrolysis rates at 20, 50 and 60°C (pH 4 and pH 7) and at 20, 30 and 50°C (pH 9) were determined in a Tier 2 study.

The substance is a mixture of two isomers (cis- and trans-). In the preliminary test, the hydrolysis rate of the cis-isomer was observed to be lower than the rate of the trans isomer. During the Tier 2 study, concentration was only based on the response of the cis isomer as it was assumed that this gives a conservative value for the half-life times. The substance is anticipated to be hydrolysed in the lactone ring forming monocyclic secondary alcohol and an acid. At pH 4 no (pseudo-) first order behaviour was observed. After an initial period the substance concentration became stable. At 50°C, a degree of hydrolysis of < 10% was observed between t=42.68 h and t=169.42 h (a period > 120 hours). From this it was concluded that the half-life time at 25°C and pH 4 is > 1 year. At pH 7 and pH 9 the substance was shown to degrade by a pseudo-first order behaviour. Half-life times at 25°C were determined from the Arrhenius equation: 17 days at pH 7 and 8.4 hours at pH 9.

Key value for chemical safety assessment

Half-life for hydrolysis:

17 d

at the temperature of:

25 °C