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Water solubility

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Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
September 2014
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:
< 1 µg/L
Temp.:
20 °C
pH:
7
Remarks on result:
other: the result as average of measurements from first and second sampling interval (6 measurements each) was 0.723 µg/L (20 °C ±0.5 °C, pH 7), which was below the limit of quantification of 1 µg/L
Details on results:
Method Validation
The analytical method on test item was validated with satisfactory results regarding linearity, limit of quantification, accuracy, precision and specificity.
Linearity: The system quantification limit was determined to be 0.3 µg/L, verified by a signal-to-noise ratio (S/N) of 36.58 for the quantifier ion trace and 1.29 for the qualifier ion trace. The determination of the limit of detection (LOD) was not deemed necessary. The analytical system gave linear response in the range of nominal 0.3 – 50 µg/L with a coefficient of determination for the linear calibration curves (r²) of = 0.992. Samples of the first sampling interval were analysed with a calibration range from 2 – 50 µg/L. A representative calibration and representative chromatograms of standards were provided in the original test report.
Limit of Quantification (LOQ)
The limit of quantification (LOQ) was defined corresponding to the study requirements and set to 1 µg/L with a dilution factor of 2 with acetonitrile containing 2 % formic acid, corresponding to a concentration of 0.5 µg/L in the final samples at 1 x LOQ, and checked by means of accuracy.
Accuracy and Precision
Mean recovery rates were 81 % for the 1 x LOQ and 98 % for the 5 x LOQ and 20 x LOQ with double distilled water, indicating sufficient accuracy of the analytical method. Furthermore, the precision of all fortification levels was satisfying because the corresponding coefficients of variation were = 17.8 %.
Specificity
Analyses were performed with highly specific LC-MS/MS (triple quadrupole mass-spectrometer). Two transitions of the same precursor ion were measured. The signals detected on the qualifier ion trace confirmed the signal identity for all analysed samples above LOQ level. Response of blank values of control samples was significantly lower than 30 % of LOQ.
Check of the Temperatures
Measured temperatures in all sampling intervals ranged from 20.03 °C to 20.13 °C (mean of 20.09 °C).
Check of the pH Values
The pH-value of each sample was determined to be 7 with special indicator stripes for each sample.
Check of Tyndall Effect
The Tyndall effect (check for colloidal matter) was negative for all samples.
Solubility Results
For each of the 12 samplings (6 samplings of 2 sampling intervals) taken at a flow rate of 0.4 mL/min, the test item could not be detected significantly above or at the quantification-level of 1 µg/L with the dilution factor of 2 taken into account. This corresponds to a water solubility of < 1 µg/L. A second run with half the flow rate was not performed.
Validity Criteria
The validity criterion regarding the repeatability could not be fulfilled as the test item was not sufficiently detectable. Temperatures were kept constant at 20 ± 0.5 °C.
Conclusions
The test item could not be detected above the limit of quantification (LOQ) of 1 µg/L.

 Sample  2-ethylhexyl 3,5,5-trimethylhexanoate [µg/L]    
   First sampling interval  Second sampling interval  
 1  0.468  0.986  
 2 0.824   0.742  
 3  0.238  0.988  
 4  0.508  0.618  
 5  0.704  1.148  
 6  0.814  0.632  Overall
 Mean  0.593  0.852  0.723
 Deviation [%]  246  86  
 SD ±  0.230  0.219  
Conclusions:
Interpretation of results (migrated information): insoluble (< 0.1 mg/L)
Water solubility: < 1 µg/L (20 °C ±0.5 °C, pH 7).
Executive summary:

The water solubility of 2-ethylhexyl 3,5,5-trimethylhexanoate was determined employing the column elution method at 20.0 ± 0.5 °C according to OECD 105 (1995) and Council Regulation (EC) No. 440/2008, Method A.6.

Analyses were performed using UPLC-MS/MS on a reversed-phase column (C 18) using external standard calibration. The method was validated with satisfactory results regarding linearity, limit of quantification, accuracy, precision, specificity and confirmation of the test item identity. The pH-values were measured with special indicator stripes. All samples were checked negative for colloidal dispersed material utilising the Tyndall effect. The test item Dragoxat® 89 could not be detected above the limit of quantification (LOQ) of 1 µg/L. Therefore, the water solubility of 2-ethylhexyl 3,5,5-trimethylhexanoate was determined to be < 1 µg/L (20 °C ±0.5 °C, pH 7).

Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2011.09.26-2011.10.06
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: guideline test following GLP principle
Remarks:
The method is not suitable for the test item.
Qualifier:
according to guideline
Guideline:
EU Method A.6 (Water Solubility)
GLP compliance:
no
Type of method:
flask method
Water solubility:
< 0.3 mg/L
Temp.:
25 °C
pH:
6.63
Conclusions:
Interpretation of results (migrated information): other: <0.3 mg/L at 25 °C
Water solubility: <0.3 mg/L at 25 °C.
Executive summary:

In a guideline test employing shake flask method, the water solubility of the test substance was determined to be lower than 0.3 mg/L at 25 °C.

Description of key information

Water solubility: < 1 µg/L (20 °C ±0.5 °C, pH 7).

Key value for chemical safety assessment

Water solubility:
1 µg/L
at the temperature of:
20 °C

Additional information

In a guideline test employing shake flask method, the water solubility of the test substance was determined to be lower than 0.3 mg/L at 25 °C. In order to improve the sensitivity of the water solubility determination, a second experiment was conducted employing the column elution method at 20.0 ± 0.5 °C according to OECD 105 (1995) and Council Regulation (EC) No. 440/2008, Method A.6. Analyses were performed using UPLC-MS/MS on a reversed-phase column (C 18) using external standard calibration. The method was validated with satisfactory results regarding linearity, limit of quantification, accuracy, precision, specificity and confirmation of the test item identity. The pH-values were measured with special indicator stripes. All samples were checked negative for colloidal dispersed material utilising the Tyndall effect. The test item could not be detected above the limit of quantification (LOQ) of 1 µg/L. Therefore, the water solubility of the test item was determined to be < 1 µg/L (20 °C ±0.5 °C, pH 7).