[1R-(1α,2β,5α)]-2-isopropyl-5-methylcyclohexyl 5-oxo-L-prolinate

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

09 - 16 April 2018

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The study was conducted according to an internationally recognised method, and under GLP. Significant variability was observed in the results. The substance is considered to be adequately characterised. Therefore validation with restrictions applies.

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

adopted 27. Jul. 1995

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

Commission Regulation (EU) No 260/2014 amending Regulation (EC) No 440/2008 adopted 24 January 2014

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

GLP certificate (inspected on 15 to 16 November 2017 / signed on 15 May 2018)

Type of method:

flask method

Remarks:

with slow-stirring adaptation (as recommended in ECHA guidance and Letinski publication)

Key result

Water solubility:

622.5 mg/L

Conc. based on:

test mat.

Loading of aqueous phase:

10 g/L

Incubation duration:

>= 1 - <= 6 d

Temp.:

20 °C

pH:

>= 5.88 - <= 7

Remarks on result:

other:

Remarks:

loading rate tested between 4 and 14 g/L without dependency of solubility perceived

The solubility of the test item in water was determined from the measured concentrations of the test item in the filtrated test solutions after extraction procedure. They are calculated following the equation cited above.

Measurements during Equilibration

The data which was acquired during equilibration time (flask 1A-C, days 1 – 4) was presented in the following table:

Table 4.8/1: Equilibration:

Day	Temperature [°C]	pH (via pH paper)	Measured Concentration [mg/L] (without taking into account all recovery rates and dilution factor)	Concentration Mean [mg/L]	Difference to previous sample [%]
1	20,5	6 - 7	135,1	751,6	-
			130,06
2	20,5	6 - 7	121,18	707,7	-5,8
			128,49
3	20,5	6 - 7	106,17	586,5	-17,1
			100,74
4	20,5	6 - 7	112,71	663,6	13,1
			112,93

During the equilibration time downward tendency was observed during the first 3 days and the difference of more than 15 % was observed in the concentrations on days 2 and 3.

Therefore, the test was prolonged and the flask 1A was further measured corresponding to the value of day 4. Due to a difference of less than 15 % in the concentrations on days 3 and 4 and no upward tendency, the test was finished and the flasks 2 – 6 were analysed in the same way.

Measurements day 6, in the flasks 2 - 6:

Table 4.8/2: Results flasks 2 - 6:

Flask	Temperature [°C]	pH (via pH meter)	Measured Concentration [mg/L] (without taking into account all recovery rates and dilution factor)	Concentration Mean [mg/L]
2	20,5	6,32	109,11	591,8
			92,13
3	20,5	5,88	82,17	499
			87,51
4	20,5	6,11	124,27	712,7
			118,05
5	20,5	6,36	116,48	684,4
			116,23
6	20,5	6,11	97,38	569,8
			96,35

Considering the concentration means obtained on flasks 2 – 6, a standard deviation of 87.1 mg/L was calculated, giving a relative standard deviation of 14.2 %.

Dependency of solubility on amount of the test item (nominal load) was not perceived.

Finally, considering that the RSD of all replicates (including results obtained on flasks 1A – 1C and 2 - 6), was lower than 15 % (13.2 %),

the equilibration time can be considered as approximately 1 day and all measurements were included in the calculation to determine the water solubility of the substance.

Note that even if the RSD of all replicates was lower than 15 %, a significant variation of the concentrations obtained in flasks 1A-C and 2-6 was observed, which may be due to micro emulsion. However, no Tyndall effect (i.e. a laser beam was not scattered when transmitted through the liquid) could be observed indicating that no colloidal dispersed particles or micells should be present.

Therefore, the water solubility of the test item was stated as 622.5 ± 82.4 mg/L corresponding to a relative standard deviation of 13.2 %.

Executive summary:

The water solubility of the test substance was measured, under GLP, according OECD 105/ EU A6 guideline, flask method with slow-stirring adaptation.

Samples were extracted and filtered. Analysis was performed using a fully validated GC-FID method.

In a first assay, equilibrium time was measured and considered to be reached after 24 hours stirring, based on 4 measurements on day 1, 2, 3 and 4 and using a loading rate of 10 g/L.

A second assay was performed with longer stirring times (6 days) using loading rates between 4 and 14 g/L. No significant loading-rate- dependency was observed.

The maximum difference calculated from the concentrations measured in all the samples was below 15%. Therefore the water solubility of the test substance was given as the mean value of all the measurements.

Finally, the water solubility of the test substance is 622.5 g/L at 20 °C, pH 5.8 -7.

Description of key information

Considered moderately soluble, with equilibrium reached at 24h. pH of saturated solution: between 5.8 and 7.

Key value for chemical safety assessment

Water solubility:

622.5 mg/L

at the temperature of:

20 °C

Additional information

A reliable experimental study, conducted according to a recognized OECD/EC optimised method, and under GLP, is available. Despite restrictions, it is considered as a key study. The result is retained as key data.