4-(cyclohexylamino)butane-1-sulfonic acid

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 May 2019 - 20 May 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2016

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Version / remarks:

2004

Deviations:

no

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)

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

PREPARATION OF THE TEST SOLUTIONS
- Test item was spiked to sterile buffers using a test item solution in tap water purified by a Milli-Q water purification system (Millipore, USA)
- Target concentration: 1 mg/L
- Each solution was filter-sterilised through a 0.2 μm FP 30/0.2 CAS filter (Whatman, Dassel, Germany) and transferred into a sterile vessel. To exclude oxygen, nitrogen gas was purged through the solution for 5 minutes.
- For each sampling time (see below), duplicate sterile vessels under vacuum were filled with 6 mL test solution.
- Blank buffers containing a similar content of blank spiking solution were treated similarly as the test samples taken at t=0.
- The vessels were placed in a temperature controlled environment in the dark at 50.1°C +/- 0.2°C.

SAMPLING DETAILS
- Samples for analysis were taken immediately after preparation (t=0), at t= 2.4 hours and at t= 5 days.
- Samples taken at t=2.4 h and 5 days were cooled to room temperature using running tap water.

DETAILS ON PRETREATMENT PRIOR TO ANALYSIS
Analysis was performed on subsamples of 40 μL. The samples were 25-fold diluted with buffer and analyzed.

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

Buffers:

- Buffer pH 4: Solution of 16.7% 0.01 M sodium acetate and 83.3% 0.01 M acetic acid in water.
- Buffer pH 7: Solution of 0.01 M potassium di-hydrogenphosphate in water adjusted to pH 7 using 1 N sodium hydroxide.
- Buffer pH 9: Solution of 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 all buffers: 0.0009% (w/v)

Details on test conditions:

TEST SYSTEM
- Measures to exclude oxygen: nitrogen gas was purged through the solutions for 5 minutes (see above)
- Measures taken to avoid photolytic effects: the test vessels were kept in the dark.

CO-SOLVENT
- The volume of the co-solvent was < 1% of the sample volume. Nominal concentrations were not corrected for the spiking volume.

DETAILS TIER 1
- pH 4.0 at 50.1 ± 0.2°C
- pH 7.0 at 50.1 ± 0.2°C
- pH 9.0 at 50.1 ± 0.2°C

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

ca. 1 mg/L

Remarks:

Initial conc. measured: see table in Results.

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

ca. 1 mg/L

Remarks:

Initial conc. measured: see table in Results.

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

ca. 1 mg/L

Remarks:

Initial conc. measured: see table in Results.

Number of replicates:

Two

Positive controls:

no

Negative controls:

no

Preliminary study:

At pH 4, pH 7 and pH 9 a decrease of substance concentration of < 10% was observed after 5 days.

No further tests were required.

Test performance:

RECOVERIES
- Recovery is the concentration analysed at t=0 relative to the nominal concentration.
- The mean (n=2) recovery at each pH was calculated (see table below).
- The mean recoveries fell within the criterion range of 90-110% for pH 4 and pH 7.
- The mean recoveries fell within the acceptable range of 70-110% for pH 9.

Transformation products:

no

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

not applicable

% Recovery:

99

pH:

4

Temp.:

50 °C

% Recovery:

96

pH:

7

Temp.:

50 °C

% Recovery:

84

pH:

9

Temp.:

50 °C

Key result

pH:

4

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

Details on results:

The preliminary study indicated that the substance is hydrolytically stable at pH 4, pH 7 and pH 9 (half-life time at 25°C is > 1 year) and no further study was performed.

Table: Tier 1 results at pH 4, pH 7 and pH 9 and 50°C 

pH	Sampling time	Analyzed concentration [mg/L]	Degree of hydrolysis [%]		Measured pH
			Individual	Mean
4	0 hours	0.991			4.1
		0.992			4.1
	2.4 hours	0.992	0.0063	-0.11	4.1
		0.994	-0.22		4.1
	5 days	0.988	0.41	0.26	4.1
		0.991	0.11		4.1
7	0 hours	0.957			7.0
		0.957			7.1
	2.4 hours	0.952	0.52	1.0	7.1
		0.942	1.5		7.1
	5 days	0.958	-0.15	-0.13	7.0
		0.958	-0.12		7.0
9	0 hours	0.843			9.1
		0.835			9.1
	2.4 hours	0.843	-0.50	-0.22	9.1
		0.838	0.056		9.1
	5 days	0.940	-12	-12	9.0
		0.934	-11		9.0

 

Conclusions:

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

Executive summary:

Hydrolysis of the substance at pH values normally found in the environment (pH 4, 7 and 9) was investigated in a GLP-compliant study according to EC C.7, OECD 111 and EPA OPPTS 835.2120. A degree of < 10% of hydrolysis was observed at pH 4, 7 and 9 after 5 days at 50°C (Tier 1). This corresponds with a half-life time at 25°C of > 1 year. The substance is concluded to be hydrolytically stable at pH 4, 7 and 9.

Description of key information

The substance is hydrolytically stable at pH values normally found in the environment (pH 4 - 9).

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C

Additional information

Hydrolysis of the substance at pH values normally found in the environment (pH 4, 7 and 9) was investigated in a GLP-compliant study according to EC C.7, OECD 111 and EPA OPPTS 835.2120. A degree of < 10% of hydrolysis was observed at pH 4, 7 and 9 after 5 days at 50°C (Tier 1). This corresponds with a half-life time at 25°C of > 1 year. The substance is concluded to be hydrolytically stable at pH 4, 7 and 9.