Alkali salt of sulfonated aryl azo amino sulfonyl aryl azo sulfonyl aryl azo aryl sulfonate

Hydrolysis

Description of key information

The test item showed a moderate hydrolysis (2.4 h < t1/2 < 20 d) at pH 7 at 20, 30 and 50 °C and at pH 9 at 10 °C. At pH 9 at 20 and 30 °C a fast elimination (t1/2 ≤ 2.4 h) of the test item was observed.

Key value for chemical safety assessment

Half-life for hydrolysis:

18.6 d

at the temperature of:

20 °C

Additional information

Hydrolysis as a function of pH was determined according to OECD Guideline No. 111 and Council Regulation (EC) No. 440/2008, Method C.7 for the test item ReactiveBrown DYHY 0331/0334.

 

Analyses of the test item components DYHY 0331 and DYHY 0334 were performed via HPLC-DAD on a reversed phase column using an external standard. Two chromatographic methods were employed, as the separation performance had to be improved for the advanced testing. The analytical methods were validated with satisfactory results in regard to linearity, accuracy, precision and specificity.

 

The preliminary test was conducted with a test item concentration of 200 mg/L (corresponding to 72.4 mg DYHY 0331/L and 42.4 mg DYHY 0334/L)in buffer solutions at pH 4, 7 and 9 and 50 °C. For pH 7 and pH 9 the advanced test was performed, as a significant reduction (> 10 %) of the test item concentration was observed in the preliminary test. At pH 4 no significant elimination was observed and therefore the test item was considered as hydrolytically stable under this condition and a half-life of > 1 year could be assumed for environmental typical temperatures.

 

The advanced test was conducted with a test item concentration of 200 mg/L (corresponding to 72.4 mg DYHY 0331/L and 42.4 mg DYHY 0334/L)in buffer solutions of pH 7 at temperatures of 20, 30 and 50 °C and pH 9 at temperatures of 10, 20 and 30 °C. Samples were taken at test start (0 h) and at at least 12 spaced points until test end, except at pH 9, 20 and 30 °C where, due to the fast transformation of the test item,only a reduced number of injections could be made. Buffer solutions were analysed at test start and test end and there was no analytical interference with the test item. Reaction rate constants and half-lives were calculated from the analysed samples and are presented in the tables below.

 

The test item showed a moderate hydrolysis (2.4 h < t_1/2< 20 d) at pH 7 at 20, 30 and 50 °C and at pH 9 at 10 °C. At pH 9 at 20 and 30 °C a fast elimination (t_1/2≤ 2.4 h) of the test item was observed.

Reaction Rate Constants and Half-Lives of the Component DYHY 0331

	pH 7			pH 9
	20 °C	30 °C	50 °C	10 °C	20 °C	30 °C
Reaction rate constantkobs [1/s]	4.30 x 10^-7	1.98 x 10^-6	3.47 x 10^-5	8.64 x 10^-6	4.33 x 10^-5	1.88 x 10^-4
Half-lifeT½[h]	448	97.2	5.55	22.3	4.45	1.02
Half-lifeT½[d]	18.6	4.05	0.23	0.93	0.19	0.04
Number of data points^1	14	16	13	21	21	5
Slope of regression graph	significantly non zero

1) = used for evaluation

Reaction Rate Constants and Half-Lives of the Component DYHY 0334

 

	pH 7			pH 9
	20 °C	30 °C	50 °C	10 °C	20 °C	30 °C
Reaction rate constantkobs [1/s]	7.70 x 10^-7	4.03 x 10^-6	6.53 x 10^-5	1.91 x 10^-5	9.19 x 10^-5	3.61 x 10^-4
Half-lifeT½[h]	250	47.8	2.95	10.1	2.10	0.533
Half-lifeT½[d]	10.4	1.99	0.12	0.42	0.09	0.02
Number of data points^1	14	13	13	19	10	3
Slope of regression graph	significantly non zero

1) = used for evaluation