Bisisobutyryl peroxide

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Juli 2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Well conducted study under GLP, according to OECD principles, certificate of analysis included in the report.

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

yes

Remarks:

screening Tier 1 was performed at 15 degree C

Principles of method if other than guideline:

Based on the information of the sponsor the test substance was known to be thermically very unstable at ambient and higher temperatures. Therefore the screening hydrolysis study (Tier 1) was performed at a test temperature of 15°C instead of the required 50°C according to the guideline.

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

At the moment the test substance was added to the buffer solutions the first sample was taken from a test vessel and analyzed using the analytical method. Depending on the tested pH value the subsequent samples were taken on different time intervals and analyzed to determine the percentage of hydrolysis. Samples were analyzed directly after sampling in order to stop the hydrolysis.

Buffers:

Sterile test buffer solutions of pH 4.0, 7.0 and 9.0 were prepared according to the description in Annex 3 of OECD 111 and purged with nitrogen for at least 5 minutes. Sterilization of the buffer solutions was performed by autoclaving at 121°C for at least 20 minutes.

Details on test conditions:

Chemicals
All chemicals used were of reagent grade quality, unless stated otherwise.
Buffer solutions of the different pH values were prepared according to the information as described in Annex 3 of OECD 111.

Materials
All glassware and buffer solutions were sterilised. Buffer solutions were flushed with nitrogen to minimise oxidation. Test vessels were kept under dark conditions to avoid eventual photo degradation. A temperature controlled water bath was used; temperature was measured using a calibrated thermometer. pH was measured using a pH meter.

Duration:

180 min

pH:

4

Temp.:

15

Initial conc. measured:

392.2 mg/L

Duration:

180 min

pH:

7

Temp.:

15

Initial conc. measured:

365.6 mg/L

Duration:

120 min

pH:

9

Temp.:

15

Initial conc. measured:

406.3 mg/L

Preliminary study:

The hydrolysis screening test was performed separately for each pH value tested. The test substance showed hydrolysis at all pH values, hydrolysis rate increased at higher pH values. The half-lives were calculated to be far less than 12 hours, the limit for conducting a water solubility test according to the REACH guidance

Test performance:

Only the screening part (Tier 1) of the hydrolysis study was conducted.

Transformation products:

not measured

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

pH value of 4
The temperature during the test varied between 14.9 and 15.0°C. It was observed that more than 85% of the test substance was hydrolyzed in 3 hours. Using the information gathered during the screening hydrolysis test also a calculation of the half-life (t ½) was determined by applying the Arrhenius relationship, the relation between the logarithmic value of the concentration of the test substance and the time. The half-life for the test substance was calculated to be 63 minutes.

pH value of 7
The temperature during the test varied between 14.8 and 15.1°C. It was observed that more than 88% of the test substance was hydrolyzed in 3 hours. Using the information gathered during the screening hydrolysis test also a calculation of the half-life (t ½) was determined by applying the Arrhenius relationship, the relation between the logarithmic value of the concentration of the test substance and the time. The half-life for the test substance was calculated to be 57 minutes.

pH value of 9
The temperature during the test varied between 14.8 and 15.1°C. It was observed that more than 93% of the test substance was hydrolyzed in 2 hours. Using the information gathered during the screening hydrolysis test also a calculation of the half-life (t ½) was determined by applying the Arrhenius relationship, the relation between the logarithmic value of the concentration of the test substance and the time. The half-life for the test substance was calculated to be 29 minutes.

pH:

4

Temp.:

15 °C

Hydrolysis rate constant:

0.011 min-1

DT50:

63 min

Type:

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

Remarks on result:

other: regression equation: y=-0.0048x+2.6169; r2=0.9989

pH:

7

Temp.:

15 °C

Hydrolysis rate constant:

0.012 min-1

DT50:

57 min

Type:

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

Remarks on result:

other: regression equation: y=-0.0053x+2.6107; r2=0.9927

pH:

9

Temp.:

15 °C

Hydrolysis rate constant:

0.024 min-1

DT50:

29 min

Type:

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

Remarks on result:

other: regression equation: y=-0.0102+2.6021; r2=0.9881

Results screening hydrolysis, pH 4

Sample	Time  from start test	Conc. (Ct)	Hydrolysis	Log Ct
	min.	mg/l	%
pH 4, t=0 min.	3	392.2	0.0	2.59
pH 4, t= 20 min.	20	329.8	15.9	2.52
pH 4, t= 40 min.	40	269.9	31.2	2.43
pH 4, t= 60 min.	60	213.1	45.7	2.33
pH 4, t= 90 min.	90	161.0	58.9	2.21
pH 4, t= 120 min.	120	110.9	71.7	2.04
pH 4, t= 180 min.	180	56.1	85.7	1.75

Results screening hydrolysis, pH 7

Sample	Time  from start test	Conc. (Ct)	Hydrolysis	Log Ct
	min.	mg/l	%
pH 7, t=0 min.	3	365.6	0.0	2.56
pH 7, t= 20 min.	20	309.9	15.2	2.49
pH 7, t= 40 min.	40	254.7	30.3	2.41
pH 7, t= 60 min.	60	205.4	43.8	2.31
pH 7, t= 90 min.	90	142.5	61.0	2.15
pH 7, t= 120 min.	120	100.7	72.5	2.00
pH 7, t= 180 min.	180	41.0	88.8	1.61

Results screening hydrolysis, pH 9

Sample	Time  from start test	Conc. (Ct)	Hydrolysis	Log Ct
	min.	mg/l	%
pH 9, t=0 min.	3	406.3	0.0	2.61
pH 9, t= 20 min.	20	264.9	34.8	2.42
pH 9, t= 40 min.	40	150.8	62.9	2.18
pH 9, t= 60 min.	60	86.1	78.8	1.94
pH 9, t= 80 min.	80	53.4	86.8	1.73
pH 9, t= 100 min.	100	37.3	90.8	1.57
pH 9, t= 120 min.	120	28.0	93.1	1.45

Calculation half-lives

		Kobs	t1/2
	slope	(min^-1)	(min)
pH 4	-0.00476812	0.010979001	63
pH 7	-0.005326768	0.012265337	57
pH 9	-0.010217028	0.023525577	29

K_obs= -ln(10) * slope

 

t_1/2= ln(2) / K_obs

Summary of method validations analytical method

Validation	Parameter	Result	Requirement
Linearity	R squared	R^2= 0.998492738 (lowest value)	R^2≥ 0.98
Reproducibility (2.5 mg/L)	Coefficient of variation	12.5%	< 20%
Reproducibility (1000 mg/L)	Coefficient of variation	1.5%	< 20%
Limit of detection		3.75 mg/L (highest value)
Recovery aqueous pH 4	Mean	76.9%	70 – 110%
	Standard deviation	3.9%	< 20%
Recovery aqueous pH 7	Mean	86.1%	70 – 110%
	Standard deviation	4.7%	< 20%
Recovery aqueous pH 9	Mean	81.4%	70 – 110%
	Standard deviation	1.6%	< 20%
System stability	Deviation control stand. from expected value	1.9 to -3.1%	< 10%

 

Validity criteria fulfilled:

yes

Conclusions:

At a pH value of 4 the half-life (t½) for diisobutyryl peroxide at a temperature of 15°C was calculated to be 63 minutes.
At a pH value of 7 the half-life (t½) for diisobutyryl peroxide at a temperature of 15°C was calculated to be 57 minutes.
At a pH value of 9 the half-life (t½) for diisobutyryl peroxide at a temperature of 15°C was calculated to be 29 minutes.
Based on the determined half-lifes, being all far less than 12 hours, no water solubility testing is required accroding to the REACH Guidance

Executive summary:

A screening hydrolysis of diisobutyryl peroxide (Trigonox 187-C30) was determined at 15°C and at the pH values of 4, 7 and 9 with GLP, in agreement with OECD guideline 111.

Based on the information of the sponsor the test substance was known to be thermically very unstable at ambient and higher temperatures. Therefore the screening hydrolysis study (Tier 1) was performed at a test temperature of 15°C instead of the required 50°C according to the guideline.

The results of this hydrolysis study will be used for determination if it is useful to conduct also a water solubility test for the test substance. If the half life would occur to be less than 12 hours no water solubility testing would be required. Therefore only the screening part (Tier 1) of the hydrolysis study was conducted.

Reference 2

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study is a research based experiment, not conducted to GLP, Not conducted to a standard guideline. Considered reliable with restrictions.

Principles of method if other than guideline:

See section 6.6: 3437 -84 -1, Additional ecotoxicological information, ter Weele, 2012.

GLP compliance:

no

Radiolabelling:

no

Analytical monitoring:

yes

Details on results:

See section 6.6: 3437 -84 -1, Additional ecotoxicological information, ter Weele, 2012.

See section 6.6: 3437 -84 -1, Additional ecotoxicological information, ter Weele, 2012.

Conclusions:

For the degradation of Diisobutryl peroxide in water it can be concluded that:

- Bisisobutyryl peroxide decomposes completely in water after 60 minutes at 27°C (room temperature).
- The decomposition products observed are: Isobutyric acid (IBA), Isopropanol, propene and acetone.
- The main decomposition/hydrolysis product found is Isobutyric acid.
- Propene is also likely to be one of the main decomposition products but the exact amount can not be determined due to its high volatile nature.

Executive summary:

See section 6.6: 3437 -84 -1, Additional ecotoxicological information, ter Weele, 2012.

Description of key information

At a pH value of 4 the half-life (t½) for diisobutyryl peroxide at a temperature of 15°C was calculated to be 63 minutes.

At a pH value of 7 the half-life (t½) for diisobutyryl peroxide at a temperature of 15°C was calculated to be 57 minutes.

At a pH value of 9 the half-life (t½) for diisobutyryl peroxide at a temperature of 15°C was calculated to be 29 minutes.

For the degradation of Diisobutryl peroxide in water it can be concluded that:

- The decomposition products observed are: Isobutyric acid (IBA), Isopropanol, propene and acetone.

- The main decomposition/hydrolysis product found is Isobutyric acid.

- Propene is also likely to be one of the main decomposition products but the exact amount can not be determined due to its high volatile nature.

Key value for chemical safety assessment

Half-life for hydrolysis:

57 min

at the temperature of:

15 °C