Tetralithium 5,5'-[vinylenebis[(3-sulphonato-4,1-phenylene)azo]]bis[3-methylsalicylate]

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)

Version / remarks:

Council Regulation EC No 440/2008

Deviations:

no

Principles of method if other than guideline:

In case compounds react chemically with water a hydrolysis reaction takes place. It’s the target of a hydrolysis study to determine whether or not and how fast a compound reacts with water. The reaction kinetics and the influence of temperature and pH-value on the stability of the test item will be determined.
In the environment chemicals usually occur in dilute solution which means that water is present in large excess. Therefore the concentration of water remains essentially constant during hydrolysis. Hence the kinetics of hydrolysis is generally pseudo-first order at a fixed pH and temperature. The hydrolysis reaction may be influenced by acidic or basic species H3O+(H+) and OH- in which case it is referred to as specific acid or specific base catalysis. The concentration of the test substance in the test water is determined as a function of time. The logarithms of the concentrations are plotted against time and the slope of the resulting straight line (assuming first-order or pseudo-first order behaviour) gives the rate constant from the formula.
kobs = - slope ∙ 2.303 (if log10 is used).
When the rate constants are known for two or more temperatures, the rate constants at other temperatures can be calculated using the Arrhenius equation.
The guideline describes a tiered approach starting with a preliminary test at 50 °C at pH 4, pH 7 and pH 9. The next steps (choice of pH-value, temperature and length of test) depend on the results of the preliminary test.
According to OECD Guideline 111 this guideline is only valid for
• Pure compounds (content greater than approx. 95 %)
• Compounds with a suitable water solubility
• Compounds for which analytical methods are available for the test item and hydrolysis products in aqueous solutions.

GLP compliance:

yes

Specific details on test material used for the study:

Storage conditions: room temperature
Date of receipt: 2016-06-20
Expiry date: 2018-06-17

Radiolabelling:

no

Analytical monitoring:

yes

Remarks:

HPLC

Details on sampling:

Storage conditions: room temperature

Buffers:

Preparation and procedure of the tests
All buffer solutions were filled in glass bottles and purged with N2 for five minutes.
Afterwards the buffer solutions were sterilized at 120 °C for 20 minutes. Before the beginning of the tests the solutions are tempered and the temperature was checked.
All glassware was purged with N2 before and after filling in the test item and the buffer solutions. The test solutions were overlain with N2.

Reagents and Materials
Buffer pH 4 Citric acid/NaOH/NaCl; Fluka, order no.: 33643
Buffer pH 7 KH2PO4/Na2HPO4, Fluka, order no.: 33646
Buffer pH 9 Na2B4O7/HCl, Fluka, order no.: 33648

Estimation method (if used):

The concentration of the test substance in the test water is determined as a function of time. The logarithms of the concentrations are plotted against time and the slope of the resulting straight line (assuming first-order or pseudo-first order behaviour) gives the rate constant from the formula.
kobs = - slope ∙ 2.303 (if log10 is used).
When the rate constants are known for two or more temperatures, the rate constants at other temperatures can be calculated using the Arrhenius equation.

Details on test conditions:

Sterility test
To prove the sterility of the glass instruments and the test design, sterility tests of each buffer solution were performed at the end of the incubation.
Result: With the bacteria count of all buffer solutions the sterility of the tests was proofed. No microbes (colonies) were found.

Solubility and test concentration
According to OECD TG 111 the concentration of the test item should not exceed 0.01 M or half of the saturation concentration of the water solubility.
The water solubility of the test item was determined as 240 g/L.
Consequently, the test item was applied as aqueous buffer solution with a concentration of approx. 200 mg/L which fulfills the requirements of OECD 111.
Clear solutions were obtained.

HYDROLYSIS AT PH 4
Hydrolysis at 50 °C
Preparation of the test solution
47.1 mg of the test item were dissolved in 200 mL buffer pH 4 resulting in a test item concentration of 203.2 mg/L (0.00028 mol/L).
Aliquots of the test solution were directly filled into brown glass sample vials to obtain individual samples for each test point. Preparation was carried out under nitrogen as flushing gas to avoid oxygen.
The vials were closed and incubated at 50 °C in a heat regulator with electronic temperature control to the exclusion of light to avoid any photolytic effects. The temperature was checked during the experiment using a digital precision thermometer. No deviations above ± 0.5 °C from the target value were obtained.
At each test point the hydrolysis solution was directly analyzed by HPLC.
The pH of the blank buffer solution was checked at the beginning of the test. Additionally the pH of the hydrolysis solution was measured at each test point.
The suitability of the HPLC system during the hydrolysis study was verified on every day of application. The calibration was verified daily at the level of 198.5 mg/L by using a control calibration solution.

HYDROLYSIS AT PH 7
Hydrolysis at 50 °C
Preparation of the test solution
46.6 mg of the test item was dissolved in 200 mL buffer pH 7 resulting in a test item concentration of 201.1 mg/L (0.00028 mol/L).
Aliquots of the test solution were directly filled into brown glass sample vials to obtain individual samples for each test point. Preparation was carried out under nitrogen as flushing gas to avoid oxygen.
The vials were closed and incubated at 50 °C in a heat regulator with electronic temperature control to the exclusion of light to avoid any photolytic effects. The temperature was checked during the experiment using a digital precision thermometer. No deviations above ± 0.5 °C from the target value were obtained.
At each test point the hydrolysis solution was directly analyzed by HPLC.
The pH of the blank buffer solution was checked at the beginning of the test. Additionally the pH of the hydrolysis solution was measured at each test point.
The suitability of the HPLC system during the hydrolysis study was verified on every day of application. The calibration was verified daily at the level of 198.5 mg/L by using a control calibration solution.

HYDROLYSIS AT PH 9
Hydrolysis at 50 °C
Preparation of the test solution
47.2 mg of the test item was dissolved in 200 mL buffer pH 9 resulting in a test item concentration of 203.7 mg/L (0.00028 mol/L).
Aliquots of the test solution were directly filled into brown glass sample vials to obtain individual samples for each test point. Preparation was carried out under nitrogen as flushing gas to avoid oxygen.
The vials were closed and incubated at 50 °C in a heat regulator with electronic temperature control to the exclusion of light to avoid any photolytic effects. The temperature was checked during the experiment using a digital precision thermometer. No deviations above ± 0.5 °C from the target value were obtained.
At each test point the hydrolysis solution was directly analyzed by HPLC.
The pH of the blank buffer solution was checked at the beginning of the test. Additionally the pH of the hydrolysis solution was measured at each test point.
The suitability of the HPLC system during the hydrolysis study was verified on every day of application. The calibration was verified daily at the level of 198.5 mg/L by using a control calibration solution.

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

203.2 mg/L

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

201.1 mg/L

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

203.7 mg/L

Statistical methods:

Repeatability
A relative standard deviation of approx. 1.1 % indicates a satisfying repeatability and precision of the method applied to quantify the test item concentrations over the test duration of 5 days. The requirements of OECD 111 are met.

Sensitivity
Regarding the chromatogram of the lowest concentration, taken from calibration measurement of repeatability tests, the analytical method is sufficiently sensitive to quantify test item concentrations down to 10 % or less of the initial concentration used in the hydrolysis experiment.

Transformation products:

not measured

% Recovery:

99.4

pH:

3.9

Temp.:

50 °C

Duration:

5 d

Remarks on result:

other: Overall degradation of test item after 5 days less than 10%, therefore stable at 50 °C at pH 4 and no half-life time and hydrolysis rate were calculated

% Recovery:

100.6

pH:

7

Temp.:

50 °C

Duration:

5 d

Remarks on result:

other: Overall degradation of test item after 5 days less than 10%, therefore stable at 50 °C at pH 7 and no half-life time and hydrolysis rate were calculated

% Recovery:

101.27

pH:

9

Temp.:

50 °C

Duration:

5 d

Remarks on result:

other: Overall degradation of test item after 5 days less than 10%, therefore stable at 50 °C at pH 9 and no half-life time and hydrolysis rate were calculated

Remarks on result:

not determinable

Remarks:

No abiotic degradation of the test item was observed. Bayscript Gelbkomponente is found to be stable at 50 °C at all three pH-values. Therefore it can be assumed that the test item is also stable at 25 °C and no half-life times and hydrolysis rates were calculated.

Results with reference substance:

No reference substance used

Validity criteria fulfilled:

yes

Conclusions:

Bayscript Gelbkomponente is found to be stable at 50 °C at all three pH-values. Therefore it can be assumed that the test item is also stable at 25 °C and no half-life times and hydrolysis rates were calculated. No abiotic degradation of the test item was observed. The tests were performed according to OECD Guidelines for Testing of Chemicals, Section 1.

Executive summary:

The tests were performed according to OECD Guidelines for Testing of Chemicals, Section 1 – Physical-Chemical Properties, OECD TG 111, Council Regulation (EC) No 440/2008, Guideline Part C – Methods for the Determination of Ecotoxicity, C.7. “Abiotic Degradation: Hydrolysis as a Function of pH”.

The hydrolysis behaviour of the test item was investigated at 50 °C at pH values of 4, 7 and 9 over a period of five days according to OECD TG 111. The stability was monitored by HPLC analysis using UV-detection.

The overall degradation of the test item at 50 °C at pH 4, 7 and 9 after 5 days was less than 10 %. Therefore the test item is considered to be stable at 50 °C at pH 4, 7 and 9.

No abiotic degradation of the test item was observed.

Bayscript Gelbkomponente is found to be stable at 50 °C at all three pH-values. Therefore it can be assumed that the test item is also stable at 25 °C and no half-life times and hydrolysis rates were calculated.

Description of key information

The tests were performed according to OECD Guidelines for Testing of Chemicals, Section 1 – Physical-Chemical Properties, OECD TG 111, Council Regulation (EC) No 440/2008, Guideline Part C – Methods for the Determination of Ecotoxicity, C.7. “Abiotic Degradation: Hydrolysis as a Function of pH”.

The hydrolysis behaviour of the test item was investigated at 50 °C at pH values of 4, 7 and 9 over a period of five days according to OECD TG 111. The stability was monitored by HPLC analysis using UV-detection.

The overall degradation of the test item at 50 °C at pH 4, 7 and 9 after 5 days was less than 10 %. Therefore the test item is considered to be stable at 50 °C at pH 4, 7 and 9.

No abiotic degradation of the test item was observed.

Bayscript Gelbkomponente is found to be stable at 50 °C at all three pH-values. Therefore it can be assumed that the test item is also stable at 25 °C and no half-life times and hydrolysis rates were calculated.