trisodium 3-amino-4-[4-[4-(2-(2-ethenylsulfonylethoxy)ethylamino)-6-fluoro-1,3,5-triazine-2-ylamino]-2-sulfophenylazo]-5-hydroxynaphthalene-2,7-disulfonate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Experiment start date - 15 March 1999; Experiment completion date - 16 April 1999; Study completion date - 23 June 1999.

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)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Identity: FAT 40'574/B
Batch: WP 23/99
Purity: Approx. 75 %
Appearance: Solid, dark-red powder
Storage: At room temperature at about 20 °C
Expiration Date: 08 February 2006

Analytical monitoring:

yes

Details on sampling:

Standard Solutions
Different standard solutions were prepared to analyse the concentration of FAT 40574/B. For example 13.18 mg of FAT 40574/B were dissolved in 100 ml of a mixture of water and acetonitrile (50:50; v/v) to prepare a stock solution of about 131.8 µg/ml FAT 40574/B. Calculated volumes of this stock solution were diluted with the above mentioned solvent mixture to obtain standard solutions in the range from 2.636 µg/ml to about 131.8 µg/ml FAT 40574/B.

Sample Preparation
After incubation 20 µl aliquots of the test solutions at each pH value were analysed without dilution by measuring the UV/VIS signal of FAT 40574/B after HPLC separation of the injected sample solution.

Buffers:

Buffer pH 4, Biphthalate
Buffer pH 7, Phosphate
Buffer pH 9, Borate/Potassium chloride/NaOH

Number of replicates:

Two

Positive controls:

no

Preliminary study:

pH 4.0: FAT 40574/B is not stable at pH 4.0. Therefore the test was performed at 50 °C to show the degradation the range of 20 % to 70 %. The half-life time of FAT 40574/B at 50.0 °C and pH 4.0 was calculated to be 16 hours (0.7 days).

pH 9.0: The results of the preliminary test show, that FAT 40574/B is not stable at pH 9.0. Therefore the test was performed at 50 °C to show the degradation the range of 20 % to 70 %. The half-life time of FAT 40574/B at 50.0 °C and pH 9.0 was calculated to be 32 hours (1.3 days).

pH 7.0: The results of pH 7.0 showed no significant degradation of FAT 40574/B at 50 °C. According to the EEC Directive 92/69, Section C.7, it can be concluded, that the estimated half-life time is higher than one year under representative environmental conditions (25 °C). Therefore, FAT 40574/B can be considered to be hydrolytically stable at pH 7.0, and no further testing was necessary at this pH-value.

Transformation products:

not measured

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

14.69 s-1

DT50:

168 h

pH:

4

Temp.:

50 °C

Hydrolysis rate constant:

154.4 s-1

DT50:

16.8 h

pH:

4

Temp.:

39 °C

Hydrolysis rate constant:

57.24 s-1

DT50:

43.2 h

pH:

4

Temp.:

39 °C

Hydrolysis rate constant:

57.6 s-1

DT50:

43.2 h

pH:

7

Temp.:

25 °C

DT50:

> 8 760 h

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

3.5 s-1

DT50:

720 h

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

78.12 s-1

DT50:

31.2 h

pH:

9

Temp.:

60 °C

Hydrolysis rate constant:

214.9 s-1

DT50:

12 h

pH:

9

Temp.:

70 °C

Hydrolysis rate constant:

669.6 s-1

DT50:

4.8 h

Details on results:

HYDROLYSIS AT pH 4.0 AND DIFFERENT TEMPERATURES
Calculation of the Half-Life Time
The hydrolysis reaction at pH 4.0 is relatively fast. Therefore, the further hydrolysis tests at pH 4.0 were performed at 39 °C in quadruplet. Each buffered test solution was analysed in time intervals. The half-life time at pH 4.0 and 39 °C was calculated to be 43 hours (1.8 days).

Evaluation of the Half-Life Time at 25 °C
The half-life time of the hydrolysis reaction of FAT 40574/B at 25 °C and pH 4.0 was calculated to be 170 hours (7 days).

HYDROLYSIS AT pH 9.0 AND DIFFERENT TEMPERATURES
Calculation of the Half-Life Time
The hydrolysis reaction at pH 9.0 is relatively slow. Therefore, the further hydrolysis tests at pH 9.0 were performed at 60 °C and 70 °C, each in duplicate. Each buffered test solution was analysed in time intervals. The half-life time at pH 9.0 and 60 °C was calculated to be 12 hours (0.5 days). The half-life time at pH 9.0 and 70 °C was calculated to be 4 hours (0.2 day).

Evaluation of the Half-Life Time at 25 °C
The half-life time of the hydrolysis reaction of FAT 40574/B at 25 °C and pH 9.0 was calculated to be 714 hours (30 days).

Validity criteria fulfilled:

yes

Conclusions:

Stable at pH 7 and to be unstable at pH 4 and 9 at 25 °C.

Executive summary:

The purpose of this study was to determine the hydrolysis behaviour of FAT 40574/B in aqueous buffered solutions adjusted to pH 4.0, pH 7.0 and pH 9.0. The study was conducted according to OECD test guideline 111 and EEC Directive C.7. The hydrolysis of the test item was performed at 50.0 °C ± 0.1 °C at each of pH 4.0, pH 7.0, and pH 9.0. As FAT 40574/B was not stable at pH 4.0 and at pH 9.0, further testing was performed at elevated temperatures in order to calculate the rate constant (k25) and the half-life time of the hydrolysis at pH 4.0, pH 9.0 and 25 °C. FAT 40574/B was found to be stable at pH 7.0 at 50 °C. The degradation at pH 7.0 and 50 °C after 120 hours was less than 10 %. Therefore no further testing was performed at this pH-value. The results are summarised below (the values typed in italics were calculated using the Arrhenius equation):

 

pH	Temperature [°C]	Reaction rate constant k[1/s]	Half-life time t½[days]
4.0	25	14.69	7
	50	154.4	0.7
	39	57.24	1.8
	39	57.60	1.8
9.0	25	3.496	30
	50	78.12	1.3
	60	214.9	0.5
	70	669.6	0.2

 

FAT 40574/B at pH 4.0 has a half-life time of 170 hours (7 days) at 25 °C. FAT 40574/B is stable at pH 7.0. Its half-life time is longer than one year at 25 °C. FAT 40574/B at pH 9.0 has a half-life time of 714 hours (30 days) at 25 °C.

Description of key information

In an hydrolysis study conducted, the substance has been found to be stable at pH 7 and to be unstable at pH 4 and pH 9.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C

Additional information

The purpose of this study was to determine the hydrolysis behaviour of FAT 40574/B in aqueous buffered solutions adjusted to pH 4.0, pH 7.0 and pH 9.0. The study was conducted according to OECD test guideline 111 and EEC Directive C.7. The hydrolysis of the test item was performed at 50.0 °C ± 0.1 °C at each of pH 4.0, pH 7.0, and pH 9.0. As FAT 40574/B was not stable at pH 4.0 and at pH 9.0, further testing was performed at elevated temperatures in order to calculate the rate constant (k25) and the half-life time of the hydrolysis at pH 4.0, pH 9.0 and 25 °C. FAT 40574/B was found to be stable at pH 7.0 at 50 °C. The degradation at pH 7.0 and 50 °C after 120 hours was less than 10 %. Therefore, no further testing was performed at this pH-value. The results are summarised below (the values typed in italics were calculated using the Arrhenius equation):

FAT 40574/B at pH 4.0 has a half-life time of 170 hours (7 days) at 25 °C.

FAT 40574/B is stable at pH 7.0. Its half-life time is longer than one year at 25 °C.

FAT 40574/B at pH 9.0 has a half-life time of 714 hours (30 days) at 25 °C.