2-phenyl-1H-benzimidazole-5-sulphonic acid

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17.08.2012 - 19.10.2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5 °C for a period of 8 days. The sample solutions were taken from the water bath at various times and the pH of each solution recorded.

Samples
An aliquot of each sample solution was diluted by a factor of 2 using acetonitrile (MeCN). Sample dilutions performed under non-actinic light.

Buffers:

Buffer solution for
pH 4: Potassium hydrogen phthalate 0.05 mol/dm3
pH 7: Disodium hydrogen orthophosphate (anhydrous) 0.03 mol/dm3, Potassium dihydrogen orthophosphate 0.02 mol/dm3 and Sodium chloride 0.02 mol/dm3
pH 9: Disodium tetraborate 0.01 mol/dm3 and Sodium chloride 0.02 mol/dm3

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

Details on test conditions:

The test item is dissolved in an aqueous solution at a specific pH value and incubated in the dark in a water bath thermostated at a specific temperature with a maximum deviation of ± 0.5 °C. The concentration of the test item is determined as a function of time, using a suitable analytical method. In the case of decreasing concentrations, the logarithms of the concentrations are plotted against time (log 10 (c t )). If the plot is a straight line, the reaction is considered to be of (pseudo-)first order. The rate constant and the half-life time are then calculated using the slope. From data generated at differing temperatures for any single pH, an estimation of the rate constant and half-life at 25 °C can be determined by the use of the Arrhenius relationship.
Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 5 x 10-2 g/L in the three buffer solutions. Sample preparation was performed under non-actinic light.
The concentration of each solution did not exceed the lesser of 0.01 mol/L or half the water solubility.
The test solutions were split into individual vessels for each data point.
The solutions were shielded from light whilst maintained at the test temperature.

Duration:

8 d

pH:

4

Temp.:

50

Initial conc. measured:

>= 0.054 - <= 0.054 g/L

Duration:

8 d

pH:

7

Temp.:

50

Initial conc. measured:

>= 0.051 - <= 0.051 g/L

Duration:

8 d

pH:

9

Temp.:

50

Initial conc. measured:

>= 0.051 - <= 0.051 g/L

Number of replicates:

Experiments were run in duplicates at each pH with test sample and standard.

Negative controls:

yes

Remarks:

MeCN : relevant buffer solution (1:1 v/v)

Preliminary study:

In a preliminary study at 50 °C at pH 4, 7 and 9 for 198 hours no significant hydrolysis (<10 %) has been observed, equivalent to a half-life of more than 1 year at 25 °C. Normally the tier 1 test would involve incubation for a period of 5 days; however, due to a sampling error no usable data was available for the 5 day time point. A subsequent time point taken after 8 days showed less than 10 % hydrolysis. As less than 10 % hydrolysis at 50 °C over 5 days equates to a half-life of greater than one year at 25 °C, the same conclusion can be drawn from less than 10 % hydrolysis over the longer period of 8 days.

Transformation products:

not measured

Key result

pH:

4

Temp.:

25 °C

DT50:

> 1 yr

Key result

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

Key result

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

The linearity of the detector response with respect to concentration was assessed over the concentration ranges of 1.06 to 53.1 mg/L in pH 4 media, 1.17 to 58.7 mg/L in pH 7 media and 1.05 to 52.6 mg/L in pH 9 media. These were satisfactory with correlation coefficients of 0.999, 1.000 and 1.000 being obtained, respectively.

Validity criteria fulfilled:

yes

Conclusions:

The test substance is hydrolytically stable under environmental conditions (half-life >1 year at pH 4, 7 and 9) and abiotic degradation is not expected.

Executive summary:

The assessment of hydrolytic stability of the test item (CAS 27503-81-7) was carried out using a procedure designed to be compatible with Method C.7 Abiotic Degradation, Hydrolysis as a Function of pH of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004. The results are as follows:

pH 4 Estimated half-life at 25 °C is >1 year

pH 7 Estimated half-life at 25 °C is >1 year

pH 9 Estimated half-life at 25 °C is >1 year

Description of key information

The test substance is hydrolytically stable under environmental conditions (half-life >1 year at pH 4, 7 and 9) and abiotic degradation is not expected.

 

Additional information

The assessment of hydrolytic stability of the test item (CAS 27503-81-7) was carried out 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 2008 and Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004. The results are as follows:

pH 4 Estimated half-life at 25 °C is >1 year

pH 7 Estimated half-life at 25 °C is >1 year

pH 9 Estimated half-life at 25 °C is >1 year