Adenine

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

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)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.8 (Partition Coefficient - Shake Flask Method)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 830.7550 (Partition Coefficient, n-octanol / H2O, Shake Flask Method)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Partition coefficient type:

octanol-water

Analytical method:

high-performance liquid chromatography

Key result

Type:

log Pow

Partition coefficient:

-0.1

Temp.:

20 °C

pH:

>= 6.5 - <= 6.8

Details on results:

Preliminary Test
The preliminary test at room temperature showed, that the octanol solubility of the test item was below 2.3 g/L.
With the estimated water solubility of 0.1 – 1.0 g/L, and the solubility in octanol of <2.3 g/L, determined from this preliminary test, the partition coefficient can be estimated to be between 0.4 and 1.4.
For the determination of the log POW in this range the shake flask method is recommended.

Main Test
The partition coefficient of the test item Adenine was determined at 22 °C (pH 6.5 – 6.8) by means of the shake-flask-method to be log POW = -0.1.

The phases of the shake-flask-method were measured twice by means of HPLC. The results of these measurements are summarized in below.

 

Concentrations in the aqueous phases

separating funnel	pH values*1	measured concentration (mg/L)	mean concentration*2 (mg/L)
1a	6.5	36.11 / 36.12	180.56
1b	6.7	34.63 / 34.71	173.36
2a	6.8	26.00 / 25.84	129.61
2b	6.6	25.59 / 25.59	127.97
3a	6.6	35.96 / 35.71	179.17
3b	6.8	35.55 / 35.54	177.72

*1 at temperatures of 22.2 – 22.5 °C

*2 under consideration of the dilution factor 5

 

Concentrations in the octanol phases

separating funnel	measured concentration (mg/L)	mean concentration*1 (mg/L)
1a	29.66 / 29.34	147.51
1b	30.27 / 30.19	151.14
2a	21.75 / 22.29	110.09
2b	22.99 / 22.75	114.35
3a	30.64 / 31.02	154.13
3b	32.34 / 32.31	161.61

*1 under consideration of the dilution factor 5 

Results of the shake-flask-method

separating funnel	total amount of test item in the separating funnel (mg)	recovery rate (%)	POW	log POW
1a	10.17	96	0.817	-0.1
1b	9.96	94	0.872	-0.1
2a	9.59	91	0.849	-0.1
2b	9.69	92	0.894	0.0
3a	9.75	92	0.860	-0.1
3b	10.02	95	0.909	0.0
mean value				-0.1
standard deviation				<0.1

 

To verify the accuracy of the analytical method four freshly prepared standard solutions (prepared with the test item) were measured in between the samples of the shake-flask-method. The results of these measurements are shown below.

Measurement of standard solutions

Standard solution (nominal value [mg/L])	Measured value [mg/L]	Recovery rate [%]
Ü-1 (40.90)	41.14	100.6
	41.49	101.4
	41.01	100.3
	41.37	101.2
Ü-2 (45.12)	45.56	101.0
	45.74	101.4
	45.65	101.2
	45.30	102.6
Ü-3 (19.84)	19.45	98.0
	19.39	97.7
	19.07	96.1
	19.31	97.3
Ü-4 (29.20)	28.74	98.4
	28.48	97.5
	29.29	100.3
	29.00	99.3

The recovery rate of the measured standard solutions was in the range from 96.1 % to 102.6 %, which shows a good accuracy of the analytical method.

Conclusions:

The partition coefficient of the test item Adenine was determined by means of the shake-flask-method to be log POW = -0.1 at 22 °C (pH 6.5 – 6.8).

Executive summary:

A study was conducted in accordance with OECD TG 107 and Regulation (EC) No 440/2008 method A.8 to determine the partition coefficient of the test substance using the shake flask method. The equilibrium concentration of the test item in both phases was determined by means of HPLC. For the preliminary test of the 1-octanol solubility increasing volumes of 1-octanol were added to an amount of the test item. After each addition of 1-octanol the mixtures were stirred for at least 30 minutes and visually checked for any unsolved particles. With the estimated water solubility of 0.1 – 1.0 g/L and the solubility in octanol of <2.3 g/L, determined from this preliminary test, the partition coefficient can be estimated to be between 0.4 and 1.4. Based on these results for the determination of the log Pow in this range the shake flask method was used. After adding the different amounts of stock solution, pre-saturated double distilled water and pre-saturated 1-octanol, the funnels were shaken for approx. 10 minutes in a shaking apparatus. After shaking the phases were allowed to separate in the funnels. Subsequently, 10 mL of each phase were centrifuged for 30 minutes at 20 °C and 15000 rpm. For the analytical measurement by means of HPLC the centrifuged clear water phases as well as the clear octanol phases were diluted from 0.2 mL to 1 mL with methanol. The pH values of all water phases were measured. The partition coefficient of the test item was determined to be log Pow = -0.1 at 22 °C (pH 6.5 – 6.8) by means of the shake-flask-method.

Description of key information

The partition coefficient of the test item Adenine was determined by means of the shake-flask-method to be log Pow = -0.1 at 22 °C (pH 6.5 – 6.8).

Key value for chemical safety assessment

Log Kow (Log Pow):

-0.1

at the temperature of:

20 °C

Additional information

A study was conducted in accordance with OECD TG 107 and Regulation (EC) No 440/2008 method A.8 to determine the partition coefficient of the test substance using the shake flask method. The equilibrium concentration of the test item in both phases was determined by means of HPLC. For the preliminary test of the 1-octanol solubility increasing volumes of 1-octanol were added to an amount of the test item. After each addition of 1-octanol the mixtures were stirred for at least 30 minutes and visually checked for any unsolved particles. With the estimated water solubility of 0.1 – 1.0 g/L and the solubility in octanol of <2.3 g/L, determined from this preliminary test, the partition coefficient can be estimated to be between 0.4 and 1.4. Based on these results for the determination of the log POW in this range the shake flask method was used. After adding the different amounts of stock solution, pre-saturated double distilled water and pre-saturated 1-octanol, the funnels were shaken for approx. 10 minutes in a shaking apparatus. After shaking the phases were allowed to separate in the funnels. Subsequently, 10 mL of each phase were centrifuged for 30 minutes at 20 °C and 15000 rpm. For the analytical measurement by means of HPLC the centrifuged clear water phases as well as the clear octanol phases were diluted from 0.2 mL to 1 mL with methanol. The pH values of all water phases were measured. The partition coefficient of the test item was determined to be log Pow = -0.1 at 22 °C (pH 6.5 – 6.8) by means of the shake-flask-method (reference 4.7 -1).