Calcium 3-hydroxy-4-[(1-sulphonato-2-naphthyl)azo]-2-naphthoate

Hydrolysis

Administrative data

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 04 Aug 2017 to 08 Dec 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Cross-reference

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2008

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Version / remarks:

2004

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.2120 (Hydrolysis of Parent and Degradates as a Function of pH at 25°C)

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Calcium 3-hydroxy-4-[(1-sulphonato-2-naphthyl)azo]-2-naphthoate

EC Number:

229-142-3

EC Name:

Calcium 3-hydroxy-4-[(1-sulphonato-2-naphthyl)azo]-2-naphthoate

Cas Number:

6417-83-0

Molecular formula:

C21H12N2O6S.Ca

IUPAC Name:

calcium 3-hydroxy-4-[(1-sulfonato-2-naphthyl)diazenyl]-2-naphthoate

Test material form:

solid: particulate/powder

Details on test material:

Appearance: red powder
Test item storage: at room temperature

Radiolabelling:

no

Study design

Analytical monitoring:

yes

Details on sampling:

PREPARATION OF THE SAMPLES
- Test item was spiked to the buffers to the target concentration of 100 µg/L.
- For each sampling time, duplicate vessels under vacuum were filled with 6 mL test solution.
- The vessels were placed in a temperature controlled environment in the dark.
- Blank buffers containing 0.1% co-solvent were treated similarly as the test samples (at t=0).

SAMPLING DETAILS
- Samples for analysis were taken immediately after preparation (t=0) and at t= 5 days.
- Samples taken at t= 5 days were cooled to room temperature using running tap water.

pH MEASUREMENTS
The pH of the test solutions (except for the blanks) was determined at each sampling point.

Buffers:

Buffer pH 4: 16.7% 0.01 M sodium acetate and 83.3% 0.01 M acetic acid in water.

Buffer pH 7: 0.01 M potassium di-hydrogenphosphate in water adjusted to pH 7 using 1 N sodium hydroxide.

Buffer pH 9: 0.01 M boric acid and 0.01 M potassium chloride in water adjusted to pH 9 using 1 N sodium hydroxide.

Details:
- Kind of water: tap water purified by a purification system (Milli-Q, Millipore)
- Sodium azide content: 0.0009% (w/v)

Details on test conditions:

TEST SYSTEM
- Sterilisation method: Each buffer was filter-sterilised through a 0.2 µm FP 30/0.2 CA-S filter (Whatman) and transferred into a sterile vessel.
- Measures to exclude oxygen: nitrogen gas was purged through the sterile buffers for 5 minutes prior to preparation of the blank and test solutions.
- Measures taken to avoid photolytic effects: the test vessels were kept in the dark.


TEST MEDIUM
- Identity of co-solvent: dimethyl sulfoxide.
- The spiking volume was < 1% of the sample volume. Nominal concentrations were not corrected for the spiking volume.


DETAILS TIER 1 STUDY
pH 4, 7, 9 at 49.6 ± 0.3°C.

Duration of test

Duration of test 1

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

ca. 100 µg/L

Remarks:

Initial conc. measured: see table in Results.

Duration of test 2

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

ca. 100 µg/L

Remarks:

Initial conc. measured: see table in Results.

Duration of test 3

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

ca. 100 µg/L

Remarks:

Initial conc. measured: see table in Results.

Number of replicates:

Two

Positive controls:

no

Negative controls:

no

Results and discussion

Preliminary study:

An increase in concentration was measured after 5 days in the tests at pH 4, 7 and 9. This could not be explained.

Since there was no decrease in concentration, it was concluded that the degree of hydrolysis at pH 4, 7 and 9 after 5 days at 50°C is < 10%. No further tests were required.

Test performance:

RECOVERIES
- Recovery is the concentration analysed at t=0 relative to the nominal concentration.
- The (mean) recoveries fell within the criterion range of 90-110% (see table below).
- Concentrations analysed in the test samples were not corrected for recovery.

Transformation products:

no

Details on hydrolysis and appearance of transformation product(s):

not applicable

Total recovery of test substance (in %)

Total recovery of test substance (in %) 1

% Recovery:

92

pH:

4

Temp.:

50 °C

Remarks on result:

other: Recoveries: 92% and 92%

Total recovery of test substance (in %) 2

pH:

7

Temp.:

50 °C

Remarks on result:

other: Recoveries:101% and 102%

Total recovery of test substance (in %) 3

% Recovery:

100

pH:

9

Temp.:

50 °C

Remarks on result:

other: Recoveries: 99% and 100%

Dissipation DT50 of parent compound

Dissipation DT50 of parent compound 1

Key result

pH:

4

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

Dissipation DT50 of parent compound 2

Key result

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

Dissipation DT50 of parent compound 3

Key result

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

Any other information on results incl. tables

Table: Tier 1 results

pH code	Sampling time	Analyzed concentration [µg/L]	Degree of hydrolysis [%]		pH
			Individual	Mean
pH 4	0 hours	92.3			4.0
		92.1			4.0
	5 days	103	-11	-9.4	4.1
		99.3	-7.7		4.1
pH 7	0 hours	102			7.0
		101			7.0
	5 days	117	-15	-17	7.0
		119	-18		7.0
pH 9	0 hours	100			9.0
		99.0			9.0
	5 days	114	-14	-16	9.0
		116	-17		9.0

 

 

Applicant's summary and conclusion

Conclusions:

The substance is hydrolytically stable at pH 4, 7 and 9 (half-life time at 25°C is > 1 year).

Executive summary:

The hydrolysis study at pH values normally found in the environment (pH 4, 7 and 9) was performed in a GLP-compliant study according to EC C.7, OECD 111 and EPA OPPTS 835.2120.

An increase in concentration was measured after 5 days in the tests at pH 4, 7 and 9. This could not be explained. Since there was no decrease in concentration, it was concluded that the degree of hydrolysis at pH 4, 7 and 9 after 5 days at 50°C is < 10%. The substance is concluded to be hydrolytically stable at pH 4, 7 and 9 (half-life time at 25°C is > 1 year).