Cyclohexanecarboxylic acid, 1-(2-ethylbutyl)-

Adsorption / desorption

Administrative data

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

November 15, 2010 - December 21, 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This study has been performed according to OECD and/or EC guidelines and according to GLP principles.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2011

Report date:

2011

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.19 (Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge Using High Performance Liquid Chromatography (HPLC))

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Media:

soil/sewage sludge

Test material

Test material information

Constituent 1

Reference substance name:

1-(2-ethylbutyl)cyclohexane-1-carboxylic acid

EC Number:

619-508-4

Cas Number:

381209-09-2

Molecular formula:

C13 H24 O2

IUPAC Name:

1-(2-ethylbutyl)cyclohexane-1-carboxylic acid

Details on test material:

- Name of test material (as cited in study report): CAT-Acid
- Stability under test conditions: stable
- Storage condition of test material: at room temperature in the dark

Radiolabelling:

no

Study design

HPLC method

Details on study design: HPLC method:

Procedure
According to the guidelines, the determination of the Koc for test substances that are ionized for at least 10% within pH 5.5 to 7.5 should be performed with both the ionized and non-ionized form.Therefore, the pKa values of the test substance were calculated using the Perrin calculation method (pKalc 5.0, module in Pallas 3.0, CompuDrug International San Francisco, CA, USA). Based on the calculations, the HPLC analysis was performed at neutral pH and pH 2.

Solutions of reference substances with known log Koc values based on soil adsorption data and the test substance were analysed. The capacity factor (k') of each compound was calculated from its retention time. The log k' values of the references substances were plotted against the known log Koc values. A linear regression program was used to calculate the calibration curve. Linear regression analysis was performed using the least squares method. The coefficient of correlation (r) was calculated. The log Koc value for the test substance was calculated by substituting its mean log k¿ in the calibration curve.

Analytical conditions (test at neutral pH)
- Instrument: Alliance Separation Module 2695 (Waters, Milford, MA, USA)
- Detector: Dual ¿ Absorbance Detector 2487 (Waters)
- Column: Hypersil BDS-CN, 150 mm x 4.6 mm i.d., dp = 5 µm (Thermo Fisher Scientific, Waltham, MA, USA)
- Column temperature: 35°C +/- 1°C
- Mobile phase: 50/50 (v/v) methanol/water
- Flow: 1 mL/min
- Injection volume: 10 µL
- UV detection: 210 nm

Analytical conditions (test at pH 2)
- Instrument: Alliance Separation Module 2695 (Waters, Milford, MA, USA)
- Detector: Dual ¿ Absorbance Detector 2487 (Waters)
- Column: Hypersil BDS-CN, 150 mm x 4.6 mm i.d., dp = 5 µm (Thermo Fisher Scientific, Waltham, MA, USA)
- Column temperature: 35°C +/- 1°C
- Mobile phase: 50/50 (v/v) methanol/water adjusted to pH 2
- Flow: 1 mL/min
- Injection volume: 10 µL
- UV detection: 210 nm

Reference substances
- For test at neutral pH: acetanilide, atrazine, monuron, 2,5-dichloroaniline, benzoic acid phenylester, fenthion, phenanthrene and 2,4-DDT
- For test at pH 2: acetanilide, monuron, benzoic acid phenylester, fenthion, phenanthrene and 2,4-DDT.
- Stock solutions of the reference substances at concentrations of approximately 1 g/L in methanol were used. The stock solutions were diluted to obtain an end solution of 50/50 (v/v) methanol/water or 50/50 (v/v) methanol/water adjusted to pH 2. The blank solution for the mixture of reference substances was 50/50 (v/v) methanol/water or 50/50 (v/v) methanol/water adjusted to pH 2.

Preparation of the test solutions
A 2085 mg/L stock solution was prepared in methanol. This stock solution was diluted to obtain an end solution of 50/50 (v/v) methanol/water or 50/50 (v/v) methanol/water adjusted to pH 2. The final concentration of the substance was 1043 mg/L. The test substance blank solution was 50/50 (v/v) methanol/water or 50/50 (v/v) methanol/water adjusted to pH 2.

Injections
The reference substance and test substance solutions were injected in duplicate. Blank solutions were analysed by single injection. The mean retention times calculated from the 2 injections were used for the calculation of the k' values.

Results and discussion

Adsorption coefficient

Adsorption coefficient 1

Type:

log Koc

Value:

3.4

Remarks on result:

other: The log Koc of the substance at neutral pH

Adsorption coefficient 2

Type:

log Koc

Value:

3.6

Remarks on result:

other: The log Koc of the substance at pH 2

Adsorption coefficient 3

Type:

Koc

Value:

2 700

Remarks on result:

other: The Koc of the substance at neutral pH

Adsorption coefficient 4

Type:

Koc

Value:

3 600

Remarks on result:

other: The Koc of the substance at pH 2

Results: HPLC method

Details on results (HPLC method):

- In the chromatogram of the test substance 1 major peak and 4 small peaks were observed (most likely originating from impurities). The total mean area of these 4 small peaks was about 2% and their log Koc values were all lower than the log Koc of the substance.

Any other information on results incl. tables

- The value of log Koc obtained from the duplicate measurements was within +/- 0.25 log units.

- The equation of the regression line for the determination of the log Koc at neutral pH was: log k'=0.314 x log Koc - 1.04 (r=0.97, n=16)

- The equation of the regression line for the determination of the log Koc at pH 2 was: log k'= 0.292 x log Koc - 1.18 (r=0.97, n=12)

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The HPLC method using soil-adsorption-reference data was applied for the determination of the adsorption coefficient (Koc) of the substance. The log Koc of the substance at neutral pH and pH 2 was 3.4 and 3.6, respectively.