[No public or meaningful name is available]

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

4 July 2003 to 27 August 2003

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)

Version / remarks:

May 1981

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

EC Comission Directive 1999/11/EC of 8 March 1999 (Official Journal No L 77/8)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

An aliquot (10 ml) of the cooled test solution was transferred into a volumetric flask (20 ml) and made to volume with either methanol (pH 7) or mobile phase (pH 9). The use of mobile phase as the diluent at pH 9 was necessary to obtain an acceptable peak shape during analysis. The diluted test and blank solutions were analysed by HPLC.

On the final day of each test, quality control stock solutions of concentration 252.0 mg/L (pH 7 test) and 1000.6 mg/L (pH 9 test) were prepared in methanol. An aliquot of each stock solution was diluted to produce solutions of concentration 25.200 and 75.600 mg/L (pH 7) and 30.018 and 50.030 mg/L (pH 9) in mobile phase. The diluted quality control solutions were analysed by HPLC concurrently with the test solutions.

Buffers:

PREPARATION OF BUFFER SOLUTION AND ADJUSTED WATER
pH 7 buffer: 0.1M potassium dihydrogen orthophosphate solution was adjusted to pH 7.0 with 1M potassium hydroxide, with the temperature of the buffer solution at 50 °C ± 0.5 °C.
pH 9 adjusted water: The pH of a quantity of double distilled water was adjusted to ca pH 9.0 at 50 °C with 1M lithium hydroxide.

Details on test conditions:

PRELIMINARY INVESTIGATION OF SOLUBILITY:
The solubility of the test substance was found to vary with pH and the concentration of dissolved salts.
The concentration of test substance dissolved at pH 4 was highest when pH adjusted water was employed (ca 1.5 mg/L). This concentration level was considered too close to the level of quantitation for the hydrolysis test to be reliably performed. At pH 7 the test substance was sufficiently soluble in the prepared buffer solution. At pH 9 the test substance was only sufficiently soluble in water adjusted to pH 9. The use of buffers at pH 9 was not possible due to the low solubility of the test substance in the presence of buffer salt.
Test solutions at pH 7 and 9 were maintained at 50 °C and the concentration of T-71 determined upon initiation and after periods of 2.4 hours and 5 days.

PROCEDURE:
A number of 100 ml volumetric flasks were calibrated at 50 °C by heating 100 ml (at 20 °C) of distilled water to 50 °C in a water bath. The flasks were then marked at their new level. Prior to the test, the volumetric flasks were rinsed with ethanol and allowed to drip dry. The buffer solutions and adjusted waters were autoclaved at ca. 122 °C for 17 minutes and then purged with nitrogen for 5 minutes prior to use.

pH7: T-71 (ca. 0.1 g) was combined with pH 7 buffer (200 ml) in a stoppered conical flask and stirred in a waterbath overnight at 20 °C. The following day the flask was removed from the waterbath and the contents filtered through a nitrocellulose membrane (0.2 µm). Two aliquots (50 ml) of the filtered saturated solution were transferred to two pre-calibrated volumetric flasks (100 ml) and equilibrated to 50 °C. Once equilibrated the flasks were made to the 50°C calibration mark with more buffer at 50 °C. A flask containing buffer only was also prepared as a blank. The flasks were shaken and aliquots (ca. 20 ml) taken from each one and transferred to a 20°C waterbath to cool for approximately 5 minutes prior to analysis. The flasks were then covered in foil and returned to the 50 °C waterbath. Further samples were taken after 2.4 hours and 5 days.

pH9: T-71 (ca. 0.1 g) was combined with pH 9 adjusted water (ca. 200 ml) in a stoppered conical and stirred in a waterbath overnight at 50 °C. The following day the flask was removed from the waterbath and the contents filtered through a nitrocellulose membrane (0.2 µm). The test solutions were prepared and sampled in the same way as the test solutions at pH 7 above.

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

> 89.892 - < 92.893 mg/L

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

> 124.72 - < 126.28 mg/L

Number of replicates:

2 per pH

Positive controls:

no

Negative controls:

no

Transformation products:

no

% Recovery:

> 94.71 - < 100.36

pH:

7

Temp.:

50 °C

Duration:

5 d

% Recovery:

> 106.46 - < 113.12

pH:

9

Temp.:

50 °C

Duration:

5 d

Key result

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

Key result

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

Details on results:

Under the test conditions, T-71 was found to undergo 2.466 % hydrolysis at pH 7 and 0 % hydrolysis at pH 9 after 5 days at 50°C.

According to the test method it can be estimated that:
10 % hydrolysis occurring in 5 days at 50 °C is equivalent to a half-life time of 1 year at 25 °C.
50 % hydrolysis occurring in 2.4 hours at 50 °C is equivalent to a half-life time of 1 day at 25 °C.
Applying these criteria to the results obtained for T-71, the half-life at 25 °C can be estimated as being greater than 1 year at pH 7 and at pH 9.

Validity criteria fulfilled:

yes

Description of key information

half-life at 25°C: > 1 year at pH 7 and at pH 9 (EU Method C7, OECD guideline 111)

Additional information

Half-life for hydrolysis > 1 year at 25 °C