Adenine

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPPTS 830.7860 (Water Solubility Generator Column Method)

GLP compliance:

no

Type of method:

column elution method

Key result

Water solubility:

1 068 mg/L

Conc. based on:

test mat.

Temp.:

20 °C

Remarks on result:

other: pH value not indicated

Conclusions:

A water solubility of 1068 mg/L at 20 °C was determined.

Executive summary:

The water solubility was determined equivalent or similar to OECD TG 105. A column elution method was used. The column was thermostatted to ±0.02 °C. The relatively high solubility of adenine caused channels to appear in undisturbed packing. To prevent these channels and ensure equilibration with the solution, the wet adenine was periodically stirred up into a slurry and allowed to settle. The saturated adenine solution emerging from the bottom of the generator column was collected and injected by syringe into a 50 µL sample loop of a liquid chromatograph for analysis. A water solubility of 1068 mg(L at 20 °C was determined.

Reference 2

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018-11-20 to 2018-12-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Key result

Water solubility:

667.2 mg/L

Conc. based on:

test mat.

Incubation duration:

72 h

Temp.:

20 °C

pH:

6.5

Details on results:

Preliminary Test
The solubility of the test item in water at room temperature was estimated to be > 0.1 g/L and < 1.0 g/L. Therefore, the flask method was performed.

Main Test
For the main test three flasks were prepared with an amount of test item and water, and one flask only with water. After stirring and centrifugation the aqueous phases were measured by means of HPLC. The solution of each flask has been measured twice. The recovery rate of the measured standard solutions was in the range from 97.5 % to 99.7 %, which shows a good accuracy of the analytical method. The water solubility at 20 °C and pH 6.5 of the test item was determined to be 667.2 mg/L.

Preliminary test for the water solubility

Amount of test item [mg]	Total volume of added water [mL]	Stirring time at RT [min]	Remark
101.42	0.1	--	not dissolved
	0.6	2*	not dissolved
	1.6	2*	not dissolved
	3.6	2*	not dissolved
	13.6	4*	not dissolved
	100	8*	not dissolved
9.98	100	980	dissolved
4.61	250	980	dissolved
4.80	500	980	dissolved

 

Results of the flask method

Flask	1b	2a	3a	4a
measured value [mg/L]	66.6 / 67.3	66.7 / 67.0	66.1 / 66.7	0 / 0
aliquot of the flask [mL]	0.1	0.1	0.1	0.1
total volume after 1^stdilution [mL]	1	1	1	1
water solubility [mg/L]	665.8 / 672.6	667.4 / 670.1	660.6 / 667.0	0 / 0
average water solubility [mg/L]	669.2	668.7	663.8	0
mean value of the water solubility [mg/L]	667.2			0
standard deviation [mg/L]	3.0			--
relative standard deviation [%]	0.5			--

Conclusions:

The water solubility of the test item was determined to be 667.2 mg/L at 20 °C and pH 6.5.

Executive summary:

The water solubility was determined according to OECD 105 using the shake flask method with HPLC analysis. In a preliminary test, in a stepwise procedure, increasing volumes of water were added at room temperature to approximately 0.1 g of the test item in a 100 mL glass-stoppered measuring cylinder. The preliminary test at room temperature revealed, that the water solubility of the test item was between 0.1 and 1.0 g/L. Amounts of the test item were weighed into each of three flasks fitted with glass stoppers. After addition of 100 mL of double distilled water to each flask the flasks were stirred at 30 °C for different periods of time (25, 49 and 73 h). After the stirring times enough precipitate remained in the flasks to ensure the saturation of the solution. After stirring at 30 °C the flasks were cooled down to 20 °C and stirred at 20 °C for another 24 h. After 24 h stirring time the contents of the flasks were centrifuged for 30 min at 20 °C with 15000 rpm. For the analytical measurement by means of HPLC the centrifuged clear aqueous phases were diluted from 0.1 mL to 1 mL with methanol. The recovery rate of the measured standard solutions was in the range from 97.5 % to 99.7 %, which shows a good accuracy of the analytical method. The water solubility of the test item was determined to be 667.2 mg/L at 20 °C and pH 6.5.

Description of key information

The water solubility  of the test item was determined to be 667.2 mg/L at 20 °C and pH 6.5.

Key value for chemical safety assessment

Water solubility:

667.2 mg/L

at the temperature of:

20 °C

Additional information

In the key study (reference 4.8 -1) the water solubility was determined according to OECD 105 using the shake flask method with HPLC analysis. In a preliminary test, in a stepwise procedure, increasing volumes of water were added at room temperature to approximately 0.1 g of the test item in a 100 mL glass-stoppered measuring cylinder. The preliminary test at room temperature revealed, that the water solubility of the test item was between 0.1 and 1.0 g/L. Amounts of the test item were weighed into each of three flasks fitted with glass stoppers. After addition of 100 mL of double distilled water to each flask the flasks were stirred at 30 °C for different periods of time (25, 49 and 73 h). After the stirring times enough precipitate remained in the flasks to ensure the saturation of the solution. After stirring at 30 °C the flasks were cooled down to 20 °C and stirred at 20 °C for another 24 h. After 24 h stirring time the contents of the flasks were centrifuged for 30 min at 20 °C with 15000 rpm. For the analytical measurement by means of HPLC the centrifuged clear aqueous phases were diluted from 0.1 mL to 1 mL with methanol. The recovery rate of the measured standard solutions was in the range from 97.5 % to 99.7 %, which shows a good accuracy of the analytical method. The water solubility of the test item was determined to be 667.2 mg/L at 20 °C and pH 6.5.

 

In a supporting study (reference 4.8 -2) the water solubility was determined equivalent or similar to OECD TG 105 (7.6 -1). A column elution method was used. The column was thermostatted to ±0.02 °C. The relatively high solubility of adenine caused channels to appear in undisturbed packing. To prevent these channels and ensure equilibration with the solution, the wet adenine was periodically stirred up into a slurry and allowed to settle. The saturated adenine solution emerging from the bottom of the generator column was collected and injected by syringe into a 50 µL sample loop of a liquid chromatograph for analysis. A water solubility of 1068 mg/L at 20 °C was determined.

 

The result of the key study was regarded as most reliable and in accordance with the results of the supporting study. Thus, 667.2 mg/L was chosen as key value for chemical safety assessment.