2,4-diethyl-9H-thioxanthen-9-one

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-05-11 - 2017-08-22

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:

column elution method

Key result

Water solubility:

< 0.66 mg/L

Conc. based on:

test mat.

Temp.:

20 °C

Remarks on result:

other: water solubility below Limit of Detection (LOD)

Preliminary Test:

The preliminary test at room temperature showed, that the water solubility of the test item was below 9.68 mg/L. The observations of the preliminary test are summarized in Table 3.

Table 3: Preliminary test for the water solubility

Amount of test item [mg]	Total volume of added water [mL]	Stirring time at RT	Remark
114.82	0.1	--	not dissolved
	0.5	--	not dissolved
	1.0	--	not dissolved
	2.0	--	not dissolved
	10.0	10 min^1)	not dissolved
	100	10 min^1)	not dissolved
9.77	100	approx. 4 days	not dissolved
4.87	250	approx. 4 days	not dissolved
4.84	500	approx. 4 days	not dissolved

¹⁾The mixtures were treated in an ultrasonic bath for 10 minutes.

The solubility of the test item in water at room temperature was estimated to be < 9.68 mg/L. Therefore, the column elution method was performed.

Main Test:

The mean value and its standard deviation from five consecutive samples taken from the saturation plateau, each measured twice, were calculated for each run. The mean concentrations calculated on two tests using different flows were compared and the repeatability was calculated, which should be better than 30 %.

Table 4: Results of column 1 (flow rate 12.5 mL/h)

Fraction	pH value	Measured concentration [mg/L]	Mean measured concentration [mg/L]	Mean concentration [mg/L]	Relative standard deviation (RSD) [%]
39	6.20 (22.2 °C)	-- --	--	--	--
40	6.45 (22.3 °C)	-- --	--
41	6.31 (22.4 °C)	-- --	--
42	6.13 (22.3 °C)	-- --	--
43	6.19 (22.2 °C)	-- --	--

As no signal of the test item could be detected in the fractions, the first column showed a value of the water solubility of < 0.66 mg/L (< LOD).

Table 5: Results of column 2 (flow rate 25.0 mL/h)

Fraction	pH value	Measured concentration [mg/L]	Mean measured concentration [mg/L]	Mean concentration [mg/L]	Relative standard deviation (RSD) [%]
76	6.14 (21.3 °C)	-- --	--	--	--
77	6.04 (21.4 °C)	-- --	--
78	6.03 (21.3 °C)	-- --	--
79	6.09 (21.4 °C)	-- --	--
80	6.11 (21.5 °C)	-- --	--

As no signal of the test item could be detected in the fractions, the second column showed a value of the water solubility of < 0.66 mg/L (< LOD).

Table 6: Results of column 3 (flow rate 25.0 mL/h, blank)

Fraction	pH value	Measured concentration [mg/L]	Mean measured concentration [mg/L]	Mean concentration [mg/L]	Relative standard deviation (RSD) [%]
76	5.78 (24.8 °C)	-- --	--	--	--
77	5.62 (24.7 °C)	-- --	--
78	5.59 (24.7 °C)	-- --	--
79	5.61 (24.8 °C)	-- --	--
80	5.83 (24.7 °C)	-- --	--

The third column showed also no test item in the water or any signals in the HPLC chromatograms.

In both columns with different flow rates no test item could be measured in the investigated fractions. Therefore, the water solubility is below the LOD of 0.66 mg/L.

To verify the accuracy of the analytical method freshly prepared standard solutions (prepared with the test item) were measured in between the samples of the column elution method. The results of these measurements are shown in Table 7. The recovery rates should lie between 90 and 110 %.

Table 7: Measurement of standard solutions

Standard solution (nominal value [mg/L])	Measured value [mg/L]	Recovery rate [%]
Standard-Ü1 (1.103)	1.063	96.4
	1.022	92.7
	1.126	102.1
	1.089	98.7
	1.094	99.2
	1.097	99.5
Standard-Ü2 (1.040)	1.055	101.4
	1.027	98.7
	1.018	97.9
	1.043	100.3
	1.053	101.2
	1.084	104.2
Standard-Ü3 (10.66)	10.78	101.1
	10.69	100.2
Standard-Ü4 (5.120)	4.98	97.3
	4.96	96.8

The recovery rate of the measured standard solutions was in the range from 92.7 % to 104.2 %, which shows a good accuracy of the analytical method.

Following the measurements, the amount of the test item in the columns was checked. For this purpose, columns 1 and 2 were each purged with 100 mL acetone. 0.05 mL of the acetone solutions were diluted to 1 mL with the eluent and measured by HPLC.

These measurements show, that 12.53 mg of the test item could be found in column 1 after the main test, which corresponds to 78.0 % of the starting amount. 11.83 mg of the test item could be found in column 2 after the main test, which corresponds to 73.6 % of the starting amount. In both columns enough test item could be found after the main tests to ensure correct performance of the test.

Conclusions:

water solubility (at 20 °C): < 0.66 mg/L [below the LOD]

Executive summary:

According to the column elution method of OECD Test Guideline 105 (and EU Method A.6) the water solubility of the test item 2,4-Diethyl-9H-thioxanthen-9-one was determined to be below the LOD: < 0.66 mg/L at 20 °C.

Reference 2

Endpoint:

water solubility

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

2018-05-16

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

1. SOFTWARE
EPIWIN v4.1

2. MODEL (incl. version number)
WSKOWWIN v1.42

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CCc1cc(CC)c2Sc3ccccc3C(=O)c2c1

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
please refer to attached QMRF

5. APPLICABILITY DOMAIN
please refer to attached QPRF

Reason / purpose for cross-reference:

other: result used as input for the model prediction

Guideline:

other: ECHA Guidance R.6

Principles of method if other than guideline:

- Software tool(s) used including version: EPIWIN v4.1
- Model(s) used: WSKOWWIN v1.42
- Model description: see field 'Attached justification'
- Justification of QSAR prediction: see field 'Attached justification'

Specific details on test material used for the study:

CCc1cc(CC)c2Sc3ccccc3C(=O)c2c1

Key result

Water solubility:

0.004 mg/L

Conc. based on:

test mat.

Temp.:

25 °C

Remarks on result:

other: based on experimental logKow of 6.5

Water solubility:

0.008 mg/L

Conc. based on:

test mat.

Temp.:

25 °C

Remarks on result:

other: based on logKow of 6.16 calculated by the model

Details on results:

The water solubility of DETX was predicted to be 0.004073 mg/L at 25°C based on the user-entered experimental logKow of 6.5.

Conclusions:

The water solubility of DETX was predicted to be 0.004073 mg/L at 25°C based on the user-entered experimental logKow of 6.5.

Executive summary:

Water solubility of DETX was predicted with the model WSKOWWIN v1.42, which is implemented in EPIWIN v4.1. The prediction is based on the experimentally measured log Kow of 6.5. The water solubility at 25°C of DETX was predicted to be 0.004073 mg/L.

Reference 3

Endpoint:

water solubility

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Study period:

2018-05-16

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

1. SOFTWARE
EPIWIN v4.1

2. MODEL (incl. version number)
WSKOWWIN v1.42

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CC(C)c1ccc2Sc3ccccc3C(=O)c2c1

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
please refer to attached QMRF

5. APPLICABILITY DOMAIN
please refer to attached QPRF

Guideline:

other: ECHA Guidance R.6

Principles of method if other than guideline:

- Software tool(s) used including version: EPIWIN v4.1
- Model(s) used: WSKOWWIN v1.42
- Model description: see field 'Attached justification'
- Justification of QSAR prediction: see field 'Attached justification'

Specific details on test material used for the study:

CC(C)c1ccc2Sc3ccccc3C(=O)c2c1

Key result

Water solubility:

0.029 mg/L

Conc. based on:

test mat.

Temp.:

25 °C

Remarks on result:

other: based on experimental logKow of 5.59

Water solubility:

0.032 mg/L

Conc. based on:

test mat.

Temp.:

25 °C

Remarks on result:

other: based on logKow of 5.54 calculated by the model

Details on results:

The water solubility of ITX was predicted to be 0.02924 mg/L at 25°C based on the user-entered experimental logKow of 5.59.

Conclusions:

The water solubility of ITX was predicted to be 0.02924 mg/L at 25°C based on the user-entered experimental logKow of 5.59.

Executive summary:

Water solubility of ITX was predicted with the model WSKOWWIN v1.42, which is implemented in EPIWIN v4.1. The prediction is based on the experimentally measured log Kow of 5.59. The water solubility of ITX was predicted to be 0.02924 mg/L at 25°C.

Description of key information

- Water solubility of 2,4-diethyl-9H-thioxanthen-9-one ("DETX", CAS 82799-44-8, EC 280-041-0) (determined using column elution method of EU Method A.6 / OECD 105; GLP): < 0.66 mg/L at 20°C [below Limit of Detection (LOD)].

- Predicted water solubility (using WSKOWWIN programme v1.42 by US EPA):

a) registration substance 2,4-diethyl-9H-thioxanthen-9-one ("DETX", CAS 82799-44-8, EC 280-041-0): 0.0041 mg/L at 25°C;

b) closely related read-across substance 2-Isopropylthioxanthone ("ITX", CAS 5495-84-1, EC 226-827-9): 0.0292 mg/L at 25°C.

- Key value for relevant environmental conditions: 0.008 mg/L (based on QSAR prediction and an additional safety factor of 2, underpinned by analytical findings on the closely related substance ITX).

Key value for chemical safety assessment

Water solubility:

0.008 mg/L

at the temperature of:

25 °C

Additional information

According to the column elution method of OECD Test Guideline 105 (and EU Method A.6) the water solubility of the test item 2,4-Diethyl-9H-thioxanthen-9-one was determined to be below the LOD.

A reliability score of 1 was assigned, in accordance with the criteria for assigning data quality in line with the principles described by Klimisch (1997).

The predicted water solubility of both thioxanthones seem to be appropriate for relevant environmental conditions as the analytical measurement of an 100 % v/v saturated solution in an OECD 202 study on ITX revealed an identical result: 0.028 mg/L; however, dependent on the test media containing various supplements and biological material, the water solubility can also be slightly higher: 0.047 mg/L (according to analytical measurements in an OECD 201 study on ITX).

A reliability score of 2 was assigned for the prediction, in accordance with the criteria for assigning data quality in line with the principles described by Klimisch (1997) and ECHA`s Practical guide [How to use and report (Q)SARs, Version 3.1, July 2016] that defines a maximum of 2.