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Type of information:
experimental study
Adequacy of study:
key study
Study period:
2007-07-03 to 2007-08-30
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP-guideline study
according to guideline
OECD Guideline 111 (Hydrolysis as a Function of pH)
GLP compliance:
Analytical monitoring:
To perform the hydrolysis at pH of 4, 7 and 9, the following buffer solutions were prepared:
pH 4: Citrate-Buffer
500 ml of 0.2 M monopotassium citrate were adjusted to pH 4 with 1 M sodium hydroxide solution (NaOH).
pH 7: Phosphate-Buffer
500 ml of 0.2 M monopotassium phosphate were adjusted to pH 7 with 1 M sodium hydroxide solution (NaOH).
pH 9: Borate-Buffer
500 ml of 0.2 M boric acid (H3BO3) in 0.2 M KCl were adjusted to pH 9 with 1 M sodium hydroxide solution (NaOH).
All buffer solutions were filled up with purified water to give a total volume of 1 litre.
Details on test conditions:
To simulate different environmental conditions, the test item was dissolved in three different buffer solutions (pH 4, 7 and 9) with concentrations corresponding to half of the saturation concentration in water. The incubation vials were agitated in water baths at three different temperatures for a maximum of 30 days. After various time intervals, samples were analysed by LC/MS to determine the hydrolysis rates.

A stock solution of Tinuvin 770 in THF was prepared for the preparation of the incubation solutions. Therefore, 18.8 mg of Tinuvin 770 were filled up with methanol to a total volume of 20 ml (c = 940 μg/ml).

Incubation Solutions
5 ml of the Tinuvin 770 stock solution (4.70 mg) were filled up with the buffer solutions to give a totalvolume of 500 ml of each pH. The resulting Tinuvin 770 concentrations were 9.40 mg/l correspondingto half of the saturation concentration of Tinuvin 770 in water. The concentration of THF
in buffer solution was 1 % (v/v). 10 ml of incubation solution were transferred into tightly closable incubation vessels with a total volume of appro. 14 ml. For every temperature (10°C, 30°C and 50°C), three sets of vessels were prepared (pH 4, pH 7 and pH 9). Every single set consisted of 16 vessels (two for every measuring point).
Each vessel was labelled unique with temperature, pH and vial number as well as a and b respectively for separation of the duplicates (e.g.: “10°C pH7 Vial1a”). To the vessels of incubation time zero, 20 μl of pure formic acid were added immediately. They were not incubated. All other vessels were transferred into shaking water baths of the desired temperature.
Based on the results of a preliminary test, appropriate time intervals for sampling were chosen. The definite sampling intervals used can be found in the raw data. The tests were conducted until 90 % hydrolysis of the test item was observed or for 30 days,
whichever came first.
Due to experimental problems, the incubations at pH9, 30°C and 50°C were repeated. Therefore, 20 vessels (for 10 data points) were prepared and incubated as described above.

Sterility Tests
To minimize the process of microbial degradation during incubation, buffer solutions were filtrated sterile and incubation vessels were rinsed with ethanol. At the end of the incubation, sterility tests were performed where hydrolysis occurred, exemplarily with the last collected vessels of 50°Cseries
for every pH, namely 50°C pH4 Vial8b, 50°C pH 9 Vial10d and 50°C pH 7 Vial8a. The solutions were filtrated with the sterility test “Sterisart alpha 2000” (Satorius) and incubated with thioglycollate medium and tryptic soy broth medium at room temperature and 32 °C, respectively.
Incubation period was 14 days.
Analytical Procedure
The identity of the test item and the hydrolysis products as well as the amount of test item in each sample was determined by LC/MS. Whenever possible, samples were analysed immediately following sampling. Prior to analysis, vessels removed from the water baths were fortified with 20 μl of pure formic acid to stop or decelerate hydrolysis. For the analysis by LC/MS, approx. 1 ml was transferred into autosampler vials, respectively. No additional extraction step was necessary. The samples not directly needed for analysis were stored below 10°C.
30 d
Initial conc. measured:
9.4 mg/L
Number of replicates:
at least 6
Positive controls:
Sebacic acid (CAS 111-20-6) and 2,2,6,6-Tetramethyl-4-piperidinol (HTMP) (CAS 2403-88-5)
Negative controls:
Blank buffer solution
Preliminary study:
A preliminary hydrolysis test showed that the test item Tinuvin 770 was hydrolytically labile after five days at 50°C and pH of 7 and 9
Test performance:
Standard deviation of the repeatability: 3.72%
For the determination of the repeatability of the analytical method, one sample, namely “10°C pH4 Vial1a” was injected six times. For the calculation of the relative standard deviation, only the area values of Tinuvin 770 were considered.

Sensitivity: LOD = 0.065%
Sensitivity was determined by measuring the signal-to-noise (S/N) ratio of the lowest reference sample (5 % - reference in sequence01-240707). The limit of detection (in %) was calculated with S/N = 3

Sterility tests were performed exemplarily for the last incubation solutions of every pH of 50°C. None of the vessels was sterile. But even though the solutions were non-sterile, the decomposition of the test item showed first order kinetics (to be concluded from the graphs “logarithm amount Tinuvin 770 vs. time” showing linearity, chapter 20). With this observation, mentionable biodegradation can be excluded.
Transformation products:
25 °C
206 d
Key result
25 °C
56.6 d
25 °C
2.03 d

Description of key information

In contact with water the test substance will hydrolyse slowly.

Key value for chemical safety assessment

Half-life for hydrolysis:
56.6 d
at the temperature of:
25 °C

Additional information

At 25 °C the test substance hydrolyses slowly with a half life of 206 days at pH 4, 56.6 days at pH 7 and a half life of 2.03 days at pH 9 (CIBA-GEIGY 2007).