Sodium 6-amino-5-[[2-[(cyclohexylmethylamino)sulphonyl]phenyl]azo]-4-hydroxynaphthalene-2-sulphonate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 April, 2014 to 02 September, 2014

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)

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

The test item solutions were prepared by adding 1 mL of a 1000 mg/L stock solution into an 100 mL volumetric flask and accurately filled up with the buffer solutions. Under argon atmosphere 2.0 mL of the test item solutions were given into several amber glass vials. The vials were closed with Teflon sealed screw caps. At the sampling time the samples were diluted with 2.0 mL acetonitrile. The concentration did not exceed 0.01 M or the half saturation concentration. The determined effective concentrations prior to storage at 50 °C were 9.49 mg/L at pH 4, 9.66 mg/L at pH 7 and 9.88 mg/L at pH 9.

Buffers:

The test was carried out at three different pH values: 4.0, 7.0 and 9.0.
For this purpose, buffer solutions were prepared using reagent grade chemicals and deionized water. Applicable buffer systems are described in the Appendix of OECD guideline 111 or BBA Merkblatt Nr.55, Teil I.
The citrate buffer pH 4, the phosphate buffer pH 7 and the borate buffer
pH 9 were prepared in a concentration of 0.05 M on the basis of the undissociated acids.
The pH value of the buffer solutions used during the test were determined with a calibrated pH meter at the selected temperature with a precision of
0.1 pH units.

Details on test conditions:

The test was carried out using a thermostatically controlled water bath at +/- 0.5 °C of the chosen temperature. The temperature was kept and
measured to within +/- 0.1 °C. Photolytic interference was avoided. All suitable precautions were taken to exclude dissolved oxygen (bubbling the
buffer with argon for five minutes before preparing the test solution).

Duration:

120 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

9.49 mg/L

Duration:

120 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

9.66 mg/L

Duration:

120 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

9.88 mg/L

Number of replicates:

4 at each pH-value

Preliminary study:

No significant changes of the content in the samples were observed. At pH 4, 7 and 9, less than 10 % of the test item were hydrolysed within 120 hours at 50 degC.

Transformation products:

not measured

% Recovery:

101.1

pH:

4

Temp.:

50 °C

Duration:

120 h

% Recovery:

99.4

pH:

7

Temp.:

50 °C

Duration:

120 h

% Recovery:

96.7

pH:

9

Temp.:

50 °C

Duration:

120 h

pH:

4

Temp.:

25 °C

DT50:

> 1 yr

Type:

(pseudo-)first order (= half-life)

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

Type:

(pseudo-)first order (= half-life)

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

Type:

(pseudo-)first order (= half-life)

Table 1:         Time course of FAT 20003/K TE concentration at pH 4 at 50 °C

Time	Determined Content of FAT 20003/K TE in Sample		Actual concentration
[h]	[mg/L]		in % of initial conc.
0	9.49	100.0
120	9.59	101.1

Table 2:         Time course of FAT 20003/K TE concentration at pH 7 at 50 °C

Time	Determined Content of FAT 20003/K TE in Sample		Actual concentration
[h]	[mg/L]		in % of initial conc.
0	9.66	100.0
120	9.60	99.4

Table 3:         Time course of FAT 20003/K TE concentration at pH 9 at 50 °C

Time	Determined Content of FAT 20003/K TE in Sample		Actual concentration
[h]	[mg/L]		in % of initial conc.
0	9.88	100.0
120	9.55	96.7

Validity criteria fulfilled:

yes

Conclusions:

The half-life time for FAT 20003/K at pH 4, 7 and 9 at 25 °C were estimated to be longer than one year.

Executive summary:

The abiotic degradation of FAT 20003/K TE as a function of pH in aqueous solution was determined according to OECD guideline 111 and EC method C.7 (440/2008). A preliminary test was performed at 50 +/- 0.5 °C at three pH values: 4.0, 7.0 and 9.0. A sufficient number of measurements were made, in order to be able to estimate whether for each pH value and at 50 °C, the half-life time (t1/2) is less than 10 % of hydrolysis after 120 hours.

No significant changes of the content in the samples were observed. At pH 4, 7 and 9 less than 10 % of the test item were hydrolysed within 120 hours at 50 °C. Hence based on the findings of the preliminary study, it was shown that the hydrolysis of FAT 20003/K TE is negligible within the pH range relevant for natural environments (pH 4 to pH 9). The half-life times at pH 4, 7 and 9 are expected to be above one year at 25 °C in each case. Because the test item is stable to hydrolysis no further hydrolysis tests are necessary.

Description of key information

The abiotic degradation of FAT 20003/K TE as a function of pH in aqueous solution was determined according to OECD guideline 111 and EC method C.7 (440/2008).A preliminary test was performed at 50 +/- 0.5 °C at three pH values: 4.0, 7.0 and 9.0. A sufficient number of measurements were made, in order to be able to estimate whether for each pH value and at 50 °C, the half-life time (t1/2) is less than 10 % of hydrolysis after 120 hours.

No significant changes of the content in the samples were observed. At pH 4, 7 and 9 less than 10 % of the test item were hydrolysed within 120 hours at 50 °C. Hence based on the findings of the preliminary study, it was shown that the hydrolysis of FAT 20003/K TE is negligible within the pH range relevant for natural environments (pH 4 to pH 9). The half-life times at pH 4, 7 and 9 are expected to be above one year at 25 °C in each case. Because the test item is stable to hydrolysis no further hydrolysis tests are necessary.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C