3-aminophenol

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From April 9, 2014 to November 26, 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Experimental test performed using standard test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

yes

Remarks:

Temperature of the determinations were not maintained at ± 0.5°C, but at ±0.7-0.8°C

Principles of method if other than guideline:

The half life of hydrolysis of test chemical was determined by using sterile aqueous buffer ( 4, 7, and 9 pH) are treated with test substance in dark at constant temperature after appropriate interval it was analysed for hydrolysis.

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

not specified

Details on sampling:

- Sampling intervals for the parent/transformation products: 0 h, 2.4 h, 24 h and 120 h for pH 4, 7 and 9, respectively for the preliminary test.
For the main test: pH 9: 20°C: 0 h, 3 d, 6 d, 8 d, 10 d, 15 d, 22 d, 28 d, 30 d; 50°C: 0 h, 1 d, 2 d, 3 d, 4 d, 7 d, 11 d, 18 d, 28, 30 d; 60°C: 0 h, 1 d, 2 d, 3 d, 4 d, 7 d, 11 d, 18 d.
- Sampling method: no data
- Sampling methods for the volatile compounds, if any: not appropriate
- Sampling intervals/times for pH measurements: At each sample time point the pH value was determined within the test samples.
- Sampling intervals/times for sterility check: A sterility conformation test was conducted at the end of the entire incubation period on the the buffer Solution. A commercially available dip slide kit (e.g. Hycon GK-T/HS, Heipha Dr. Müller GmbH, Eppelheim, Germany) was used for a total count of microorganisms and to determine the total count of yeast and moulds. Dip Slides were incubated at least for 5 days at 20°C ± 2°C.
- Sample storage conditions before analysis: Immediately after sampling, the samples were diluted by a factor of 2 with ACN to stop the hydrolysis process. Prior to HPLC analysis samples were diluted further by a factor of 10 with ACN/HPLC-H2O 1:1 v/v resulting in an overall dilution factor of 20.
- Other observation, if any (e.g.: precipitation, color change etc.): no data

Buffers:

- pH: Three pH fro the preliminary test (pH4, 7, 9). One for the main test.
- Type and final molarity of buffer: see below
- Composition of buffer: see below

The buffer solutions were prepared as stated below. Each solution was diluted by a factor of 10 with HPLC-water. The pH of each buffer solution was checked with a calibrated pH-meter. The buffer solutions were purged with nitrogen gas for 10 min and sterilized by heating in an autoclave (121°C, 15 min) before using it to prepare the test solutions.

pH 4 (Pre-Test):
C6H5Na3O7 buffer
90 mL tri-sodiumcitrate dihydrate solution (about 14.7 g C6H5Na3O7 in 500 mL pure water) were mixed with 410 mL of acetic acid solution (0.1 M CH3COOH) and filled up to 1000 mL.

pH 7 (Pre-Test):
KH2PO4 buffer
400 mL potassium dihydrogen phosphate solution (6.8 g KH2PO4 in 500 mL pure water) were mixed with 232 mL of a sodium hydroxide solution (0.1 M) and filled up to 1000 mL with pure water.

pH 9 (Pre-Test and Main-Test):
Boric acid buffer
400 mL boric acid solution (3.1 g H3BO3 in 500 mL 0.1 M potassium chloride solution) were mixed with 170 mL of a sodium hydroxide solution (0.1 M) and filled up to 1000 mL with pure water.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: Stoppered glass flasks were used for carrying out the tests. All glassware was sterilised before usage by heating in an autoclave (121°C, 15 min).
- Sterilisation method: The buffer solutions were purged with nitrogen gas for 10 min and sterilized by heating in an autoclave (121°C, 15 min)
- Lighting: Darkness
- Measures taken to avoid photolytic effects: Darkness
- Measures to exclude oxygen: no data
- Details on test procedure for unstable compounds: no data
- Details of traps for volatile, if any: not appropriate
- Is the test system closed/open : Stoppered glass flasks were used
- Is there any indication of the test material adsorbing to the walls of the test apparatus? No data

TEST MEDIUM
- Volume used/treatment: The test concentration was in the range of 214-247 mg/L.
- Kind and purity of water: pure water
- Preparation of test medium: The stock solution of the test item was prepared in HPLC-water/acetonitrile 70:30 v/v with a concentration of 10 g/L.
Preliminary Test: The test samples were prepared in duplicate. An aliquot of 4 mL of the stock solution was pipetted to 200 mL of each buffer solution resulting in applied concentrations of 209-211 mg/L. Aliquots of the test solution were transferred to the incubation vessels.
The final concentration did not exceed 0.01 M in water and the content of organic solvent in the aqueous phase was kept ≤ 1% v/v.
Main Test: The test samples were prepared in duplicate. An aliquot of 5 mL of the application solution was pipetted to 250 mL of the buffer solution resulting in applied concentrations of 214-247 mg/L. Aliquots of the test solutions were transferred to the reaction vessels.
The final concentration did not exceed 0.01 M in water and the content of organic solvent in the aqueous phase was kept ≤ 1% v/v.
- Renewal of test solution: no

OTHER TEST CONDITIONS
- Adjustment of pH: see buffer solutions above
- Dissolved oxygen: no data

Duration:

30 d

pH:

9

Temp.:

20 °C

Initial conc. measured:

214 mg/L

Duration:

30 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

247 mg/L

Duration:

18 d

pH:

9

Temp.:

60 °C

Initial conc. measured:

217 mg/L

Number of replicates:

Preliminary test: 12 samples per pH value.
Main Test: 20 samples at 60°C, 22 samples at 20°C and 50°C, respectively.

Positive controls:

no

Negative controls:

no

Statistical methods:

No data

Preliminary study:

The test item was dissolved in aqueous solutions buffered at pH 4, 7 and 9 and incubated at 50 ± 0.7°C for a maximum of 5 days. At pH 4 and 7 the test item was found to be stable. After 5 days of incubation recovery values of the test item were in the range of 99-101% of the applied concentration. No further tests were carried out at these pH values.
In case of samples incubated at pH 9 degradation of the test item was observed. After 5 days of incubation 55% of the applied test item concentration could be recovered. A main test was performed at pH 9.

Test performance:

The test was performed at pH 9. Half-lives, reaction rate constants and Arrhenius parameters were calculated for three temperatures.

Transformation products:

not measured

Remarks:

Transformation products were not investigated in detail.

% Recovery:

84

pH:

9

Temp.:

20 °C

Duration:

30 d

% Recovery:

41

pH:

9

Temp.:

50 °C

Duration:

30 d

% Recovery:

13

pH:

9

Temp.:

60 °C

Duration:

18 d

pH:

9

Temp.:

20 °C

Hydrolysis rate constant:

0.004 d-1

DT50:

190 d

Remarks on result:

other: r2=0.392

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

0.026 d-1

DT50:

26 d

Remarks on result:

other: r2=0.765

pH:

9

Temp.:

60 °C

Hydrolysis rate constant:

0.153 d-1

DT50:

5 d

Remarks on result:

other: r2=0.976

Other kinetic parameters:

Arrhenius parameters:
pH9, 20°C: ln k(obs)= -5.61311; 1/T [K-1]=3.41E-3; -E/R=-8375; E [kJ/mol]= 70; ln A=23; A [d-1]= 8.22E+9
pH9, 50°C: ln k(obs)= -3.64211; 1/T [K-1]=3.09E-3; -E/R=-8375; E [kJ/mol]= 70; ln A=23; A [d-1]= 8.22E+9
pH9, 60°C: ln k(obs)= -1.87945; 1/T [K-1]=3.00E-3; -E/R=-8375; E [kJ/mol]= 70; ln A=23; A [d-1]= 8.22E+9
k(obs) = hydrolysis rate constant, measured at different temperatures
E = activation energy [kJ/mol]
T = absolute temperature [K]
R = gas constant [8.314 J/mol*K]
A = pre-exponential factor

Details on results:

TEST CONDITIONS
- pH: pH 9: The pH value was in the range of 8.5-9.1 (except for two samples taken after 18 days of incubation at 60°C: 8.1 and 8.2)
- sterility: Sterility of the buffer solutions was confirmed since no colonies were found after incubation of the dip slides with the test samples.
- temperature : Main-Test: 20°C ± 0.8°C ; 50°C ± 0.7°C; 60°C ± 0.7°C
- Anomalies or problems encountered (if yes): NO

PATHWAYS OF HYDROLYSIS
- Description of pathway: no data

SUPPLEMENTARY EXPERIMENT (if any): RESULTS: No

Results of recoveries at pH=9 (main test)

Temperature	Incubation Period	Recovery	Mean	Temperature	Incubation Period	Recovery	Mean	Temperature	Incubation Period	Recovery	Mean
20°C	[d]	[% applied]	[% applied]	50°C	[d]	[% applied]	[% applied]	60°C	[d]	[% applied]	[% applied]
	0	100.6	100.0		0	100.2	100.0		0	99.8	100.0
	0	99.4			0	99.8			0	100.2
	3	93.1	95.9		1	89.2	93.5		1	96.8	95.2
	3	98.7			1	97.8			1	93.6
	6	84.7	88.6		2	79.2	79.4		2	87.4	85.6
	6	92.5			2	79.5			2	83.9
	8	85.4	85.1		3	77.1	77.0		3	72.3	72.7
	8	84.8			3	76.9			3	73.0
	10	82.9	82.3		4	70.3	70.0		4	52.7	52.5
	10	81.8			4	69.7			4	52.4
	15	82.1	82.0		7	44.7	48.7		7	31.0	31.8
	15	82.0			7	52.8			7	32.6
	22	82.0	81.6		18	37.7	43.3		11	15.0	16.1
	22	81.1			18	48.9			11	17.1
	28	81.3	81.3		28	37.8	37.9		18	7.01	7.9
	28	81.3			28	38.0			18	8.7
	30	84.5	84.0		30	36.6	41.4
	30	83.5			30	46.3

Applied concentration: pH 9, 20°C = 214 mg/L

Applied concentration: pH 9, 50°C = 247 mg/L

Applied concentration: pH 9, 60°C = 217 mg/L

Validity criteria fulfilled:

yes

Conclusions:

The test item was observed to be hydrolytically stable at pH 4 and pH 7. Degration of the test item was observed at pH 9 with half-lives measured in the range of 5-190 days. Reaction rate constants k (obs) were determined to be 0.0036 d-1 at 20°C, 0.0262 d-1 at 50°C and 0.1527 d-1 at 60°C with corresponding half-lives of 190 d, 26 d and 5 d, respectively. By considering half life values at differnt temperature it is concluded that test chemical s negligible to slowly hydrolysable.

Executive summary:

The determination of the Abiotic Degradation of test chemical (Hydrolysis as a Function of pH) was conducted according to OECD 111 and GLP. Samples were incubated in the dark, at 50° for the pre-test and 20, 50 and 60°C for the main test. The test concentration was in the range of 209-247 mg/L. The final concentration did not exceed 0.01 M in water and the content of organic solvent in the aqueous phase was kept ≤ 1% v/v. The test chemical was observed to be hydrolytically stable at pH 4 and pH 7. After 5 days of incubation at 50°C recovery values of the test chemical were 99% of the applied concentration. Degradation of the test chemical was observed at pH 9 with half-lives measured in the range of 5-190 days. Reaction rate constants k (obs) were determined to be 0.0036 d-1 at 20°C, 0.0262 d-1 at 50°C and 0.1527 d-1 at 60°C with corresponding half-lives of 190 d, 26 d and 5 d, respectively. By considering half life values at differnt temperature it is concluded that test chemical is negligible to slowly hydrolysable.No further characterisation or identification of unknown transformation products was conducted.

Description of key information

The test item was observed to be hydrolytically stable at pH 4 and pH 7. Degration of the test item was observed at pH 9 with half-lives measured in the range of 5-190 days. Reaction rate constants k (obs) were determined to be 0.0036 d-1 at 20°C, 0.0262 d-1 at 50°C and 0.1527 d-1 at 60°C with corresponding half-lives of 190 d, 26 d and 5 d, respectively. By considering half life values at differnt temperature it is concluded that test chemical is negligible to slowly hydrolysable.

Key value for chemical safety assessment

Half-life for hydrolysis:

190 d

at the temperature of:

20 °C

Additional information

The determination of the Abiotic Degradation of test chemical (Hydrolysis as a Function of pH) was conducted according to OECD 111 and GLP. Samples were incubated in the dark, at 50° for the pre-test and 20, 50 and 60°C for the main test. The test concentration was in the range of 209-247 mg/L. The final concentration did not exceed 0.01 M in water and the content of organic solvent in the aqueous phase was kept ≤ 1% v/v. The test chemical was observed to be hydrolytically stable at pH 4 and pH 7. After 5 days of incubation at 50°C recovery values of the test chemical were 99% of the applied concentration. Degradation of the test chemical was observed at pH 9 with half-lives measured in the range of 5-190 days. Reaction rate constants k (obs) were determined to be 0.0036 d-1 at 20°C, 0.0262 d-1 at 50°C and 0.1527 d-1 at 60°C with corresponding half-lives of 190 d, 26 d and 5 d, respectively. By considering half life values at differnt temperature it is concluded that test chemical is negligible to slowly hydrolysable.No further characterisation or identification of unknown transformation products was conducted.