Benzenesulfonamide, N-(4-hydroxyphenyl)-

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

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
/

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 100 mg/L in the three buffer solutions. Due to the solutions being hazy, the solutions were then filtered through 0.2 μm Nylon membrane filters. After filtration, the solutions were observed to be free from undissolved material. The test solutions were split into individual vessels for each data point. The solutions were shielded from light whilst maintained at the test temperature. An aliquot of each sample was diluted by a factor of two using methanol.

Buffers:

buffer solution
pH 4:
Citric acid: 0.06 mol dm-3
Sodium chloride: 0.04 mol dm-3
Sodium hydroxide: : 0.07 mol dm-3
pH7
Disodium hydrogen orthophosphate (anhydrous): 0.03 mol dm-3
Potassium dihydrogen orthophosphate: 0.02 mol dm-3
Sodium chloride: 0.02 mol dm-3
pH9
Disodium tetraborate: 0.01 mol dm-3
Sodium chloride: 0.02 mol dm-3

These solutions were subjected to ultrasonication and degassing with nitrogen to minimize dissolved oxygen content.

Estimation method (if used):

/

Details on test conditions:

Tier 1
Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5 °C for a period of at least 288 hours. Due to issues with some of the standard solutions/test results, the Preliminary Test/Tier 1 was then repeated.

Tier 2
Results from the Preliminary Test/Tier 1 showed it was necessary to undertake further testing at pH 9, with solutions being maintained at 60.0 ± 0.5 °C and 70.0 ± 0.5 °C.

The concentration of the sample solution was determined by high performance liquid chromatography (HPLC).

Standards
Duplicate standard solutions of test item were prepared in methanol: relevant buffer solution (50:50 v/v) at a nominal concentration of 50 mg/L.
Duplicate standard solutions of test item were prepared in methanol: purified water (50:50 v/v) at a nominal concentration of 50 mg/L (Tier 2 only)

Duration:

288 h

pH:

9

Duration:

288 h

pH:

7

Temp.:

50

Duration:

288 h

pH:

4

Temp.:

50

Number of replicates:

1

Negative controls:

yes

Remarks:

methanol

Statistical methods:

The decrease in concentration (preliminary test) or the degree of hydrolysis was calculated using the formula:
Degree of hydrolysis in % = [(C0 - Ct)/C0 ] · 100
where:
C0 = concentration of time 0
Ct = concentration of time t

Transformation products:

yes

No.:

#1

No.:

#2

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

Based on the chemical structure of the test item, the hydrolysis products were considered to be benzenesulphonic acid (CAS 98-11-3) and p-toluidine (CAS 106-49-0).

pH:

4

Temp.:

25 °C

DT50:

> 1 yr

Type:

not specified

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

Type:

not specified

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

> 62.6 d

Type:

not specified

Validity criteria fulfilled:

yes

Conclusions:

Rate constant at pH 9: 4.61 E-4 /hour
Estimated half-life at 25°C at pH 4 and 7: > 1 year
Estimated half-life at 25°C at pH 9: 62.6 days

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C