RSS-4, DRY SUBSTANCE

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 March 2012- 15 May 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

(2008)

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:

The concentration of the substance in the test samples was determined immediately after preparation (t=0) and after 5 days. The samples taken at t= 5 days were cooled to room temperature using running tap water. In the repeated test at pH 4, concentrations were determined at t=0 and at several sampling points after t= 0 including t= 5 days.

Buffers:

Acetate buffer pH 4, 0.01 M: solution of 16.7 % (v/v) 0.01 M Sodium acetate and 83.3 % (v/v) 0.01 M acetic acid. The buffer contains 0.0009 % (w/v) Sodium azide.

Phosphate buffer pH 7, 0.01 M: solution of 0.01 M Potassium di-hydrogenphosphate adjusted to pH 7 using 1 N Sodium hydroxide. The buffer contains 0.0009 % (w/v) Sodium azide.

Borate buffer pH 9, 0.01 M: solution of 0.01 M boric acid and 0.01 M Potassium chloride adjusted to pH 9 using 1 N Sodium hydroxide. The buffer contains 0.0009 % (w/v) Sodium azide.

Details on test conditions:

The buffer solutions were filter-sterilised through a 0.2 µm filter and transferred into a sterile vessel. To exclude oxygen, nitrogen gas was purged through the solution for 5 minutes. Test substance was spiked to the solutions at a target concentration of 5 mg/L using a spiking solution in methanol (<1 % of the sample volume). For each sampling time, duplicate sterile vessels under vacuum were filled with 6 mL test solution and placed in the dark in a temperature controlled environment at 49.5 °C ± 0.1 °C. The pH of each of the test solutions (except for the blanks) was determined at each sampling time.

Preliminary test: pH 4, 7 and 9 (5 days)
Repeated preliminary test: pH 4 (5 days)

Number of replicates:

Two

Positive controls:

no

Negative controls:

yes

Remarks:

no test substance was detected in the blank buffer solutions

Preliminary study:

At pH 7 and pH 9, < 10 % of hydrolysis was observed after 5 day (half-life time at 25 °C is > 1 year). According to the guideline, no further tests were required.

10 % of hydrolysis was measured after 5 days (at pH 4). In a repeated test, < 10 % of hydrolysis (7 % was measured) was measured after 5 days (at pH 4). From this it was concluded that the degree of hydrolysis is < 10 % after 5 days at pH 4 and no higher Tier test need to be performed at pH 4.

Transformation products:

not measured

% Recovery:

107

pH:

4

Temp.:

50 °C

Duration:

0 h

% Recovery:

95

pH:

4

Temp.:

50 °C

Duration:

0 h

% Recovery:

120

pH:

7

Temp.:

50 °C

Duration:

0 h

% Recovery:

121

pH:

9

Temp.:

50 °C

Duration:

0 h

Key result

pH:

4

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

7

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

9

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Details on results:

Recovery given above is the mean concentration analysed at t=0 relative to the nominal concentration.The mean recoveries of the test substance containing buffer pH 4 solutions at t=0 fell within the criterion range of 90-110%. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test substance. The mean recoveries of the of the test substance containing buffer pH 7 and 9 solutions at t=0 were 120% and 121%. These mean recoveries were accepted since hydrolysis studies focus on a relative concentration decrease.

Table  Hydrolysis of the substance at pH 4, pH 7 and pH 9 at 50.0 ± 1.0 °C (preliminary test)

 

pH code	Sampling time	Analysed concentration [mg/L]	Degree of hydrolysis [%]		Actual pH
			Individual	Mean
pH 4	0 hours	5.33			4.0
		5.33			4.0
	5 days	4.87	8.7	10	4.2
		4.73	11		4.2
pH 7	0 hours	5.88			7.0
		6.07			7.0
	5 days	5.88	1.7	1.4	7.0
		5.90	1.2		7.0
pH 9	0 hours	6.00			9.0
		6.06			9.0
	5 days	5.83	3.3	3.6	8.9
		5.80	3.8		8.9

 

 

Table Hydrolysis of the substance at pH 4 at 50.0 ± 1.0 °C (repeated test-pH 4)

 

Sampling time [hours]	Analysed concentration [mg/L]	Relative concentration [%]	Logarithm relative concentration	Actual pH
0	4.67	97	1.99	4.1
0	4.96	103	2.01	4.1
23.5	5.21	108	2.03	4.1
23.5	5.19	108	2.03	4.1
98.5	4.62	96	1.98	4.2
98.5	4.89	102	2.01	4.2
120	4.38	91	1.96	4.2
120	4.54	94	1.97	4.2

 

 

Validity criteria fulfilled:

yes

Conclusions:

A hydrolysis study was carried out according to EC C.7, OECD 111, EPA OPPTS 830.2120 and according to the principles of GLP. At pH 4, 7 and 9 (50 °C), < 10 % of hydrolysis was observed after 5 days. Therefore the half-life time at 25 °C is > 1 year and the substance can be considered hydrolytically stable at pH 4, 7 and 9.

Description of key information

 At pH 4, 7 and 9 (50 °C) < 10 % of hydrolysis was observed after 5 days. Therefore the half-life time at 25 °C is > 1 year and the substance can be considered hydrolytically stable at pH 4, 7 and 9.

Key value for chemical safety assessment

Half-life for hydrolysis:

365 d

at the temperature of:

25 °C

Additional information

A hydrolysis study was carried out according to EC C.7, OECD 111, EPA OPPTS 830.2120 and according to the principles of GLP. 10 % of hydrolysis was measured after 5 days (at pH 4). In an additional test, < 10 % of hydrolysis (7 % was measured) was measured after 5 days (at pH 4). From this it was concluded that the degree of hydrolysis is < 10 % after 5 days at pH 4 and no higher Tier test need to be performed at pH 4.