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Water solubility

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water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
05 October to 31 October 2011
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
EU Method A.6 (Water Solubility)
GLP compliance:
yes (incl. QA statement)
Type of method:
flask method
Water solubility:
0.6 g/L
20 °C
> 5.29 - < 5.61
Remarks on result:
other: mean water solubility

Test Results for Ethyl 2-methylbutyrate:

Date: 10/10/2011 - 26/10/2011

Operator: G. Jordan

SOP Reference: CTL SOP No. 406B


Sample Preparation: The test material was tested in the as received condition in accordance with the EC440/2008 protocol.


Preliminary Estimation: The aqueous solubility of Ethyl 2-methylbutyrate was estimated by incrementally adding known amount of water to 6.8 mg of the test material in a vial. After each addition of the known amount of water, the mixture was shaken vigorously for about 10 minutes and then visually checked for any un-dissolved parts of the sample. This process was repeated until complete dissolution of the sample occurred. See details below (primary estimation) for the amount of sample and the volume of water in which complete dissolution occurred. The aqueous solubility was estimated from the amount of sample to volume of water as 0.68 g/L. Shaking equilibration was therefore selected for the analysis.


Preliminary estimation:

Mass of sample (mg): 6.8

Volume of water in which sample dissolves (ml): 10

Estimated solubility (g.L-1): < 1

Analysis method: Shake flask

Estimated Water Solubility (g.L-1): 0.68

Apparatus, Reagents, Method and Test Conditions:

Equipment: UV Spectrometer

Detector: UV

Wave length (nm): 225

Temperature of determination: 20


Reagents used: HPLC Water (pH 5.67), Standard solutions of pH 4.01 (lot #HCB816919), pH 7.00 (lot # BCBC6809) and 10.01 (lot # 3435).


Saturation of Water with Ethyl 2-methylbutyrate: To minimise the effect of emulsion formation during saturation, about 0.136 g of the test material was used to saturate 100 mL of water in each flask (labelled flask 1, flask 2 and flask 3). The three flasks were then shaken at a temperature of 30°C in an incubated shaker at 200 rpm. The flasks were shaken for durations of 24 hours (flask 1), 48 hours (Flask 2) and 72 hours (Flask 3). Each flask was then allowed to equilibrate for 96 hours prior to concentration analysis. The solutions in the flasks were visually analysed for suspension of sample droplets but no sign of emulsion was observed.


Analysis of Saturated Solutions: A set of cells with path length 1 cm was selected for the UV-spectrophotometric analysis of the test material. The cells were scanned and found to be transparent over the whole range of spectrum of the UV spectrophotometer (190 nm to 1100 nm).The cells were thoroughly cleaned and rinsed several times with the blank solution. Due to the low aqueous solubility of the sample (from the estimated result), octanol was employed as the blank and also used for the preparation of calibration solutions. The instrument was set to scan the blank solution from 1100 nm to 190 nm to obtain a baseline spectrum. The baseline spectrum did not record absorbance readings ≥± 0.02 units from nominal zero.


Calibration Graph: Calibration solutions of concentration 0.215gL-1 to 4.309 gL-1 of the test material were prepared with octanol. The solutions were analysed using the Shimadzu UV1650 PC spectrophotometer. The concentrations of the solutions with the respective absorbance are shown in the table below (Calibration Graph). An analytical wavelength of 225 nm was selected for the analysis. Graph 10.A in the attached report shows the calibration graph obtained with the solutions. The calibration was found to be leaner at the analytical wavelength with respect to the concentrations.


Calibration Graph:

Concentration (g/L)  Absorbance 1  Absorbance 2  Mean Absorbance    

          0.000                      0.02                 0.02                    0.02

          0.215                      0.12                 0.12                    0.12

          1.077                      0.54                 0.52                    0.53

          2.155                      1.00                 1.00                    1.00

          3.591                      1.64                 1.63                    1.64

          4.309                      1.94                 1.95                    1.95


m= 0.4463      C= 0.0310      r2= 0.9998


Analytical Determination of the Aqueous Solubility: The pH of the saturated solutions were analysed using Hannah Temperature - pH apparatus. Prior to the pH determinations, the performance of the apparatus was a verified using reference solutions of pH 4.01, 7.00 and 10.01; and found to be working within acceptable criteria.


The concentration of the saturated solutions were also analysed using the Shimadzu PC1650 PC spectrophotometer.


The table below (Analytical Determinations) contains the pH and absorption index of the saturated solutions. From the absorbance and the calibration graph the mean water solubility of Ethyl 2-methylbutyrate was determined as 0.6 gL-1.


The aqueous solubility result obtained was verified by adding 26 ml of water to 15.8 mg of the test material in a vial. The vial was shaken vigorously by hand for a period of about 10 seconds. The entire sample was found to have gone into solution.


Analytical Determinations:


Flask No.   pH  Absorbance 1   Absorbance 2 Mean concentration (g/L)

      1        5.61         0.27                    0.27                    0.605

      2        5.29         0.26                    0.26                    0.583

      3        5.36         0.28                    0.26                    0.605


Mean water solubility (gL-1): 0.6

Interpretation of results: moderately soluble (100-1000 mg/L)
Water solubility is 0.6 g/l at 20°C

Description of key information

Water solubility has been determined to be 0.6g/L at 20°C

Key value for chemical safety assessment

Water solubility:
0.6 g/L
at the temperature of:
20 °C

Additional information