1,4-naphthoquinone

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

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

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products:
- Sampling method: Samples were taken directly from vessels. Samples were taken and filtered using a pretreatment filter. These samples were then cooled and analysed via HPLC.
- Sampling intervals/times for pH measurements:
20°C pH 7: days 0, 13, 17, 21, 24, 27 and 30 (7 in total).
20°C pH 9: All measurements (7 in total) taken on the first day.
40°C pH7: days 0, 1, 2 and 3 (7 samples taken in total).
40°C pH9: All measurements (7 in total) taken on the first day.
50°C pH7: days 0 and 1(7 in total).
50°C pH9: All measurements (7 in total) taken on the first day.

- Sampling intervals/times for sterility check: Not conducted
- Sample storage conditions before analysis: analysed soon after sampling
- Other observation, if any (e.g.: precipitation, color change etc.): None noted

Buffers:

- pH: 7 and 9
- Composition of buffer: pH7 (Mixture of 0.1N NaOH and 0.1 M KH2PO4 diluted in ultrapure water. pH 9 (Mixture of 0.1N NaOH and 0.1M KCl/0.1M H3BO3 diluted in ultrapure water. pH 9 (Mixture of 0.1N NaOH and 0.1M KCl/0.1M H3BO3 diluted with ultra-pure water.

Estimation method (if used):

Not applicable

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: Glass culture bottle or glass flask with a test volume of 300 mL
- Sterilisation method: Not specified
- Lighting: shielded from light
- Is there any indication of the test material adsorbing to the walls of the test apparatus? No
TEST MEDIUM
- Volume used/treatment: 300 mL of test solution (10 mg/L)
- Kind and purity of water: Ultra-pure water
- Preparation of test medium: The test substance was weighed then dissolved and diluted with acetonitrile to prepare a stock solution. Aliquots of this stock solution were sampled and added to appropriate buffer solutions in a flask for shaking or culture bottle.
- Renewal of test solution: Not conducted
- Identity and concentration of co-solvent: Acetonitrile (concentration not specified)
OTHER TEST CONDITIONS
- Adjustment of pH: Not specified
- Dissolved oxygen: Not specified

Duration:

30 d

pH:

7

Temp.:

20 °C

Initial conc. measured:

ca. 10 mg/L

Duration:

0 d

pH:

9

Temp.:

20 °C

Initial conc. measured:

ca. 10 mg/L

Duration:

3 d

pH:

7

Temp.:

40 °C

Initial conc. measured:

ca. 10 mg/L

Duration:

0 d

pH:

9

Temp.:

40 °C

Initial conc. measured:

ca. 10 mg/L

Duration:

1 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

ca. 10 mg/L

Duration:

0 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

ca. 10 mg/L

Number of replicates:

7 Replicates were used for each pH/temperature.

Positive controls:

no

Negative controls:

yes

Remarks:

Buffer solutions

Statistical methods:

Not applicable

Preliminary study:

In the Tier 1 test, the substance was added to buffer solutions of pH 4, 7 and 9. After 5 days of treatment at 50°C a concentration of the test substance was measured in the buffer solutions. As a result, the test substance was considered hydrolytically stable at pH 4 because the hydrolysis of the test substance was less than 10%. The test substance was considered hydrolytically unstable at pH 7 and 9 as hydrolysis was greater than 10%. Accordingly the Tier 2 assesment was conducted at pH 7 and 9.

Test performance:

The test was considered valid if recovery of the test item was between 90 and 110% and the method is suitably sensitive. These criteria were met indicating the validity of the test.

Transformation products:

no

Remarks:

Hydrolysis of the test substance was observed at pH 7 and 9 with multiple peaks detected on the HPLC chromatogram. Attempts were made using LC/MS to identify these although this was not possible.

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

Molecular weights of around 170 to 500 were inferred to the molecular weight of the test substance (158.16), so that a change in the quinone structure of the test substance and polymerisation were presumed, but the structural formulas themselves could not be identified.

% Recovery:

99.7

pH:

7

Temp.:

20 °C

Duration:

30 d

% Recovery:

100

pH:

7

Temp.:

40 °C

Duration:

3 d

% Recovery:

100

pH:

7

Temp.:

50 °C

Duration:

1 d

% Recovery:

96.7

pH:

9

Temp.:

20 °C

Duration:

0 d

% Recovery:

100

pH:

9

Temp.:

40 °C

Duration:

0 d

% Recovery:

98.7

pH:

9

Temp.:

50 °C

Duration:

0 d

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.002 h-1

DT50:

12 d

Type:

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

Remarks on result:

other: Result extrapolated from graph using Arrhenius data

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0.159 h-1

DT50:

4 h

Type:

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

Remarks on result:

other: Result extrapolated from graph using Arrhenius data

pH:

7

Temp.:

20 °C

Hydrolysis rate constant:

0.001 h-1

DT50:

21 d

Type:

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

pH:

7

Temp.:

40 °C

Hydrolysis rate constant:

0.01 h-1

DT50:

2.9 d

Type:

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

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

0.03 h-1

DT50:

23 h

Type:

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

pH:

9

Temp.:

20 °C

Hydrolysis rate constant:

0.096 h-1

DT50:

7.3 h

Type:

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

pH:

9

Temp.:

40 °C

Hydrolysis rate constant:

0.618 h-1

DT50:

1.1 h

Type:

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

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

1.37 h-1

DT50:

0.5 h

Type:

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

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes
- Anomalies or problems encountered (if yes): No

MAJOR TRANSFORMATION PRODUCTS
Could not be conclusively identified although a change in test structure and polymerisation were presumed.

PATHWAYS OF HYDROLYSIS
- Description of pathways: Not identified.

Results with reference substance:

Not applicable

Validity criteria fulfilled:

yes

Conclusions:

The test substance is considered hydrolytically unstable at pH 7 and 9. It is assumed based on the results that the substance would be more readily hydrolysed in alkaline conditions as opposed to acidic conditions.

Description of key information

A GLP, guideline OECD 111 study is available providing hydrolysis data on the substance. The key value is interpolated from values at 20, 40 and 50°C using the Arrhenius equation to 25°C and pH 7.

The substance is more hydrolytically unstable at a higher alkaline pH although will hydrolyse at environmentally relevant temperatures and pH values.

Key value for chemical safety assessment

Half-life for hydrolysis:

12 d

at the temperature of:

25 °C