p-benzoquinone

Partition coefficient

Administrative data

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

19.07.2018 - 19.07.2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline 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:

OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)

Version / remarks:

1995

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method A.8 (Partition Coefficient - HPLC Method)

Deviations:

no

GLP compliance:

no

Type of method:

flask method

Partition coefficient type:

octanol-water

Test material

Test material information

Constituent 1

Reference substance name:

p-benzoquinone

EC Number:

203-405-2

EC Name:

p-benzoquinone

Cas Number:

106-51-4

Molecular formula:

C6H4O2

IUPAC Name:

1,4-benzoquinone

Test material form:

solid: particulate/powder

Study design

Analytical method:

high-performance liquid chromatography

Results and discussion

Partition coefficient

Key result

Type:

log Pow

Partition coefficient:

>= 0.1 - <= 0.3

Temp.:

23 °C

pH:

>= 4.8 - <= 5.3

Any other information on results incl. tables

Preliminary Tests

The preliminary test of study CSL-18-141.06 at room temperature showed, that the octanol solubility of the test item was between 16.4 and 24.0 g/L.

Table: Preliminary test for the octanol solubility

Total amount of test item [mg]	Total volume of added octanol [mL]	Stirring time at RT [min]	Remark
98.87	20	45	dissolved
327.18		125	dissolved
479.06		45	not dissolved

With the estimated water solubility of the test item (1.0 – 7.5 g/L) and the estimated solubility in octanol (16.4 – 24.0 g/L) the partition coefficient log P_OW can be estimated to be between 0.5 and 1.2.

For the determination of the log P_OW at this value the shake flask method or HPLC method are recommended.

Main Test

The phases of the shake-flask-method were measured twice by means of HPLC. The values represented in the table are rounded values. The calculation was carried out with the original not rounded values.

Table: Concentrations in the aqueous phases

separating funnel	pH values^*1	measured concentration (mg/L)	mean concentration^*2(mg/L)
1a	5.3	25.63 / 25.42	255.25
1b	5.1	25.01 / 25.27	251.42
2a	5.2	20.83 / 20.21	205.20
2b	5.2	20.51 / 20.56	205.39
3a	5.0	29.78 / 29.20	294.89
3b	4.8	30.13 / 29.49	298.07

^*1at temperatures of 23.0 – 23.7 °C

^*2under consideration of the dilution factor 10

Table: Concentrations in the octanol phases

separating funnel	measured concentration (mg/L)	mean concentration^*1(mg/L)
1a	39.00 / 39.38	391.87
1b	40.09 / 39.71	399.02
2a	33.10 / 33.45	332.73
2b	33.25 / 33.44	333.44
3a	39.92 / 39.88	399.01
3b	45.12 / 44.65	448.84

^*1under consideration of the dilution factor 10

In the Table the total amount of test item found in the two phases, the recovery rate and the partition coefficients are shown. As 20 mL of the stock solution were added to each separating funnel, each funnel should contain 20.05 mg of the test item.

Table: Results of the shake-flask-method

separating funnel	total amount of test item in the separating funnel (mg)	recovery rate (%)	POW	log POW
1a	20.78	103.6	1.535	0.2
1b	20.99	104.7	1.587	0.2
2a	21.52	107.3	1.621	0.2
2b	21.55	107.5	1.623	0.2
3a	19.78	98.6	1.353	0.1
3b	20.90	104.2	1.506	0.2
mean value				0.2
standard deviation				0.1

To verify the accuracy of the analytical method two fresh prepared standard solutions for theaqueous phase (prepared with the test item) were measured twice in between the samples of the shake-flask-method.

Table: Measurement of standard solutions

Standard solution (nominal value [mg/L])	Measured value [mg/L]	Recovery rate [%]
Ü1 (21.76)	23.55	108.2
	23.68	108.8
Ü2 (41.26)	44.98	109.0
	45.27	109.7

The recovery rate of the measured standard solutions was in the range from 108.2 % to 109.7 %, which shows a sufficient accuracy of the analytical method.

Applicant's summary and conclusion

Conclusions:

The partition coefficient log P of p-benzoquinone was determined to be 0.2 ± 0.1 at 23°C using the shake-flask-method.

Executive summary:

The partition coefficient of the test item p-Benzoquinone was determined at 23 °C (pH 4.8 – 5.3) by means of the shake-flask-method, according to OECD Test Guideline 107 (1995) to be:

log P_OW = 0.2 ± 0.1