tert-butyl α,α-dimethylbenzyl peroxide

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

January 2013 to March 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study (OECD 123) with minor deviation

Qualifier:

according to guideline

Guideline:

OECD Guideline 123 (Partition Coefficient (1-Octanol / Water), Slow-Stirring Method)

Deviations:

yes

Remarks:

A sampling time point was taken at 122h; this sampling was separated from the former sampling (118h) by a period of 4 hours instead of 5 hours minimum as specified in the guideline. this deviation does not have any impact on the result.

GLP compliance:

yes (incl. QA statement)

Type of method:

shake-flask method to: flask method

Partition coefficient type:

octanol-water

Analytical method:

high-performance liquid chromatography

Type:

log Pow

Partition coefficient:

4.4

Temp.:

25 °C

pH:

7.6 - 7.9

Details on results:

See "Any other information on results incl. tables"

The results in the two phases at each time are given in the following table:

  

Vessel Number and Sampling time	Concentration in the aqueous phase (mg/L)	Concentration in the 1-octanol phase (mg/L)	Pow Ratio	Log Pow
13-006 Y1 T = 98H	0.84	19550	23273.8	4.37
13-006 Y2 T = 98H	0.78	19250	24679.5	4.39
13-006 Y3 T = 98H	0.78	19350	24807.7	4.39
13-006 Y1 T = 118H	0.84	18900	22500.0	4.35
13-006 Y2 T = 118H	0.78	19300	24743.6	4.39
13-006 Y3 T = 118H	0.76	19150	25197.4	4.40
13-006 Y1 T = 122H	0.80	18950	23687.5	4.37
13-006 Y2 T = 122H	0.74	18850	25473.0	4.41
13-006 Y3 T = 122H	0.74	18750	25337.8	4.40
13-006 Y1 T = 138H	0.74	19000	25675.7	4.41
13-006 Y2 T = 138H	0.74	18900	25540.5	4.41
13-006 Y3 T = 138H	0.72	18450	25625.0	4.41
13-006 Y1 T = 143H	0.78	19600	25128.2	4.40
13-006 Y2 T = 143H	0.76	19750	25986.8	4.41
13-006 Y3 T = 143H	0.72	19300	26805.6	4.43

 

 

The average value of log Pow of the different vessel units is calculated as the average of the results of the individual experimental units weighed with their respective variances.

 

The results are shown in the following table.

  

Vessel Y1	Mean value Y1	Standard Deviation Y1	Vessel Y2	Mean value Y2	Standard Deviation Y2	Vessel Y3	Mean value Y3	Standard Deviation Y3
4.37 4.35 4.37 4.41 4.40	4.38	0.000480	4.39 4.39 4.41 4.41 4.41	4.40	0.000096	4.39 4.40 4.40 4.41 4.43	4.41	0.000184

  

Mean/vessel	Variance	Weighed average
4.38	0.000480	4.40
4.40	0.000096
4.41	0.000184

 

 

Conclusions:

Using the low stirring method, it was shown that the weighted average value of the 1-octanol/water partition coefficient log10 Pow of tert-butyl cumyl peroxide is equal to 4.40 ± 0.02 at 25 ± 1 °C.

Executive summary:

The partition coefficient n-octanol/water (Kow) of tert-butyl cumyl peroxide was estimated using the slow-stirring method. The Kow test was performed in accordance with the OECD 123 guideline. It was shown that the weighted average value of the 1-octanol/water partition coefficient log10 Pow of the substance is equal to 4.40 ± 0.02 at 25 ± 1 °C.

Description of key information

Using the slow stirring method, it was shown that the weighted average value of the 1-octanol/water partition coefficient log10 Pow of tert-butyl cumyl peroxide is equal to 4.40 ± 0.02 at 25 ± 1 °C.

Key value for chemical safety assessment

Log Kow (Log Pow):

4.4

at the temperature of:

25 °C

Additional information

The partition coefficient n-octanol/water (Kow) of tert-butyl cumyl peroxide was firstly determined by applying the HPLC method according to OECD Guideline 117. Two peaks were detected. The first peak shows a mean log Kow at 3.50 and the other peak a mean log Kow at 4.94. It’s assumed that the second peak corresponds to the test substance with a measured log Kow (= 4.94) similar to the estimation with QSAR model KowWin (= 4.66).

However it's known that the HPLC method is not accurate and overestimates results. As a consequence the partition coefficient n-octanol/water (Kow) of tert-butyl cumyl peroxide was then estimated using the slow-stirring method. The Kow test was performed in accordance with the OECD 123 guideline. It was shown that the weighted average value of the 1-octanol/water partition coefficient log10 Pow of the substance is equal to 4.40 ± 0.02 at 25 ± 1 °C which is considered as key value.