2-methylhydroquinone

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24.07.2018 - 25.07.2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1995

Deviations:

no

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

Analytical method:

high-performance liquid chromatography

Key result

Type:

log Pow

Partition coefficient:

0.9

Temp.:

27 °C

pH:

>= 4.8 - <= 5.3

Preliminary Tests

The preliminary test of study CSL-18-0142.06 at room temperature showed, that the octanol solubility of the test item was >117.8 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
134.34	20	30	dissolved
294.75		40	dissolved
805.02		70	dissolved
1269.64		75	dissolved
1969.20		990	dissolved
2355.97		85	dissolved

With the estimated water solubility of the test item (29.0 – 65.3 g/L) and the estimated solubility in octanol (> 117.8 g/L) the partition coefficient log P_OW can be estimated to be >0.6.

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 (mg/L)
1a	5.8	53.81 / 54.95	54.38
1b	5.4	54.00 / 54.07	54.04
2a	5.8	50.14 / 52.02	51.08
2b	5.7	51.83 / 50.53	51.18
3a	5.5	94.82 / 93.95	94.38
3b	5.6	93.29 / 92.39	92.84

^*1at temperatures of 26.9 – 27.8 °C

Table: Concentrations in the octanol phases

separating funnel	measured concentration (mg/L)	mean concentration^*1(mg/L)
1a	90.01 / 90.66	451.68
1b	89.41 / 90.92	450.82
2a	86.92 / 84.43	428.40
2b	84.54 / 86.83	428.42
3a	149.00 / 149.43	746.06
3b	142.53 / 143.52	715.13

^*1under consideration of the dilution factor 5

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 21.50 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	19.15	89.1	8.306	0.9
1b	19.11	88.9	8.343	0.9
2a	19.18	89.2	8.386	0.9
2b	19.18	89.2	8.371	0.9
3a	18.70	87.0	7.905	0.9
3b	18.02	83.8	7.703	0.9
mean value				0.9
standard deviation				<0.1

To verify the accuracy of the analytical method four 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 (61.01)	60.40	99.0
	57.27	93.9
Ü2 (140.58)	137.66	97.9
	132.37	94.2
Ü3 (79.54)	74.79	94.0
	75.67	95.1
Ü4 (111.74)	109.34	97.9
	109.92	98.4

The recovery rate of the measured standard solutions was in the range from 93.9 % to 99.0 %, which shows a sufficient accuracy of the analytical method.

Conclusions:

The partition coefficient log P of methylhydroquinone was determined to be 0.9 at 27°C using the shake-flask-method.

Executive summary:

The partition coefficient of the test item Methylhydroquinone was determined at 27°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 = 0.9 ± <0.1

Description of key information

The partition coefficient log P_OW of methylhydroquinone was determined to be 0.9 at 27°C using the shake-flask-method.

Key value for chemical safety assessment

Log Kow (Log Pow):

0.9

at the temperature of:

27 °C