REAKTIV-ORANGE DYPR 934

Hydrolysis

Administrative data

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1999-02-24 to 1999-03-26

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study according to EU method C7

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

1999

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes

Test material

Test material information

Constituent 1

Details on test material:

- Name of test material (as cited in study report): Reaktiv-Orange DYPR934

Study design

Analytical monitoring:

yes

Details on sampling:

PREPARATION OF TEST SAMPLE:
Solutions of the test substance were prepared by weighing between 10 and 11 mg of the test substance in a 50 mL volumetric flask and dissolving in the relevant buffer. The resulting solution was subjected immediately to the hydrolytically procedure.
PREPARATION OF THE STANDARDS
The calculation standards were freshly prepared by weighing between 5 and 11 mg of the standard test substance in a 50 mL volumetric flask and dissolving in the relevant buffer or in a buffer in which the test substance is hydrolytically stable.

Buffers:

pH 4:
COMPOSITION OF THE BUFFER:
21.008 g citric acid were dissolved in 200 mL sodium hydroxide solution (1 mole/L). The solution was filled up to a volume of 1000 mL with water. 560 mL were taken and 44 mL of hydrochloric acid (1 mole/L) were added and filled up to a volume of 1000 mL with distilled water.
pH 7:
COMPOSITION OF THE BUFFER:
13.61 g potassium dihydrogen phosphate were dissolved in 100 mL distilled water. 29.63 mL of sodium hydroxide (1mole/L) were added to 500 mL of this solution and filled up to a volume of 1000 mL with destilled water.
pH 9:
COMPOSITION OF THE BUFFER:
7.46 g of potassium chloride and 6.184 g of boric acide were dissolved in 1000 mL water. 500 mL of this solution were added to 21.3 mL sodium hydroxide (1mole/L) and filled up to a volume of 1000 mL with water.

Details on test conditions:

Hydrolysis test procedure
The flask containing the hydrolysis mixture was placed in a thermostatically mixture controlled water bath at the selected temperature for the specified time. Thereafter it was cooled immediately. The pH was controlled. The HPLC analysis of the unhydrolysed test substance (both main compounds) was peroformed without any delay.

Duration of test

Duration of test 1

Duration:

9 d

pH:

4

Temp.:

25 °C

Initial conc. measured:

>= 196 - <= 224 mg/L

Duration of test 2

Duration:

11.4 d

pH:

4

Temp.:

25 °C

Initial conc. measured:

>= 196 - <= 224 mg/L

Duration of test 3

Duration:

5.8 d

pH:

7

Temp.:

25 °C

Initial conc. measured:

>= 196 - <= 224 mg/L

Duration of test 4

Duration:

9 d

pH:

7

Temp.:

25 °C

Initial conc. measured:

>= 196 - <= 224 mg/L

Duration of test 5

Duration:

2.4 h

pH:

9

Temp.:

25 °C

Initial conc. measured:

>= 196 - <= 224 mg/L

Positive controls:

not specified

Negative controls:

no

Results and discussion

Preliminary study:

Yes see tables and comments "any other results incl. tables"

Test performance:

Preliminary test. A preliminary test was performed on the substance at 50 ± 0.1 °C at each of pH 4.0, 7.0 and 9.0.
The decomposition at pH 9 was higher than 50 % after 2.4 hours at 50 °C for the main compound (I) as well as for the main component (II).
REMARKS: According to the guideline, if less than 10 per cent of the reaction is observed after 5 days
(t1/2 > 1 year), the chemical is considered hydrolytically stable and no additional testing is required. If the substance is known to be unstable at environmentally relevant temperatures, the preliminary test is not required. The analytical method must be sufficiently precise and sensitive to detect a reduction of 10 per cent in the initial concentration. In the Study the substance (Component (I) and component (II)) is considered INSTABLE at pH 9. According to the guideline a half-life period of less than one day under environmental conditions (25 °C) may be estimated. No further test was necessary.

Transformation products:

not measured

Dissipation DT50 of parent compound

Dissipation DT50 of parent compound 1

pH:

4

Temp.:

50 °C

Hydrolysis rate constant:

0.03 s-1

DT50:

22.2 h

Dissipation DT50 of parent compound 2

pH:

4

Temp.:

60 °C

Hydrolysis rate constant:

0.08 s-1

DT50:

8.5 h

Dissipation DT50 of parent compound 3

pH:

4

Temp.:

70 °C

Hydrolysis rate constant:

0.16 s-1

DT50:

4.3 h

Dissipation DT50 of parent compound 4

pH:

4

Temp.:

25 °C

DT50:

231.3 h

Dissipation DT50 of parent compound 5

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

0.12 s-1

DT50:

5.7 h

Dissipation DT50 of parent compound 6

pH:

7

Temp.:

35 °C

Hydrolysis rate constant:

0.02 s-1

DT50:

36.3 h

Dissipation DT50 of parent compound 7

pH:

7

Temp.:

25 °C

DT50:

138.6 h

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes
- Anomalies or problems encountered (if yes):None

Any other information on results incl. tables

Remarks:

Due to the fact that the test substance contains two main components the hydrolysis rates were calculated separately for each main component in the following way:

The initial concentration (c (0)) of the test substance and the concentration of the standard (c (standard)) were calculated from the sample weights. The concentration during the test process (c (t)) was calculated from the HPLC peak area of the respective main component in comparison with the HPLC peak area of the respective component in the standard solution using the formula:

C=(C (standard) Peak Area (sample))/(Peak Area (standard))

In the case of pseudo first reaction, according to the following relationships a linear dependence of l is expected for log (c (t)/c(0))

log (c(t)/c(0) = -(k/2.303).t

-log (c(t)/c(0))= (k/2.303).t

The experimental data of test 1 were checked graphically for the approximate fulfilling of this relationship. The constant Kobs was determined by linear regression of -log (c (t)/c (0) to t. The half-life period t1/2=ln2/kobs

The Arrhenius Equation

logk=-A/T + B was used to extrapolate the rate constants at higher temperatures to room temperature.

Applicant's summary and conclusion

Conclusions:

At pH 9 the decomposition is higher than 50% after 2.4 hours at 50°C for both main components. Thus the test substance may be considered hydrolytically instable at pH 9. According to the guideline a half-life period or less than one day under environmental conditions (25°C) may be estimated.

Executive summary:

At pH 9 the decomposition is higher than 50% after 2.4 hours at 50°C for both main components. Thus the test substance may be considered hydrolytically instable at pH 9. According to the guideline a half-life period or less than one day under environmental conditions (25°C) may be estimated.