2-ethylhexyl 12-(acetoxy)octadecanoate

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

Read-Across Justification is attached below.

Reason / purpose for cross-reference:

read-across source

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Media:

other: HPLC method

Radiolabelling:

no

Test temperature:

Column temperature : 40ºC

Details on study design: HPLC method:

Test System
The determination was carried out using the HPLC screening method, designed to be compatible with Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001.
The test system utilized a high performance liquid chromatograph. A commercially available cyanopropyl reverse phase HPLC column containing lipophilic and polar moieties was used.

Performance of the Test
-Preparation of sample solution
Test item (0.1514 g) was diluted to 100 mL with acetonitrile to give a concentration of 1.514 g/L.
-Preparation of dead time solution
The dead time was determined by measuring the retention time of formamide (purity 99.94%, 644 mg/L solution in 55:45 acetonitrile: purified water).
-Preparation of reference standard solutions
Solutions of reference standards (see the table) were prepared in methanol.

Determination of retention time
The sample, dead time and reference standard solutions were injected in duplicate using the following HPLC parameters:
HPLC System :
- Agilent Technologies 1200 series, incorporating autosampler and workstation
- Polymer Laboratories Evaporative Light Scattering Detector 1000 (ELSD)
Column :
- Waters XSelect HSS Cyano 5mm (150 x 4.6 mm id)
Column temperature :
- 40ºC
Mobile phase :
- 55:45 v/v Acetonitrile: purified water 100% Acetonitrile post 15 minutes (after DDT peak elution) pH of mobile phase : 8.18
Flow-rate :
- 1.0 mL/min
Injection volume :
- 10 μl (samples)
- 100 mL (standards)
UV detector wavelength (standards) :
- dead time and reference standards: 210 nm
ELS detector (samples) :
- Evap temperature : 80 °C
- Nebulizer temperature: 40 °C
- Gas flow: 1.0 mL /min

Calculation
Construction of calibration curve
A calibration curve was constructed from the retention time data of the dead time and reference standard solutions. The capacity factors k' for the reference standards were calculated using the equation below.

Adsorption coefficient of sample
The capacity factor was calculated using the following equation:
k' = ( tr – t₀ ) / t₀
where:
k' = capacity factor
tr = retention time (min)
t₀ = dead time (min)

and the log₁₀Koc value determined using the following equation with reference to the calibration curve.
Log₁₀ Koc = ( log₁₀ k' – A ) / B
where:
Koc = adsorption coefficient
k' = capacity factor
A = intercept of the calibration curve
B = slope of the calibration curve

A correlation of log k' versus log Koc of the calibration standards was plotted using linear regression.

The mobility classification of the test item was obtained by comparing the calculated Koc value to the mobility classes according to P.J. McCall, R.L. Swann, D.A. Laskowski, S.M. Unger, S.A. Vrona and H.J. Dishburger “Estimation of Chemical Mobility in Soil from Liquid Chromatography Retention Times”; Bull. Environm. Contam. Toxicol. 24, 190-195 (1980).

Range of Koc // Mobility Class
0-50 = Very high
50-150 = High
150-500 = Medium
500-2000 = Low
2000-5000 = Slightly
>5000 = Immobile

Analytical monitoring:

not specified

Key result

Sample No.:

#1

Type:

log Koc

Value:

> 5.63 dimensionless

pH:

8.18

Temp.:

40 °C

Sample No.:

#1

Type:

Koc

Value:

> 427 000 dimensionless

Conclusions:

Read-Across is claimed between BT4 (target) and SE7B (Source), according to the justification attached to the target record, and based on structural and physical/chemical similarities.

Analogue diesters (SE7B, SE6B) and BT4 contain the same functional groups, i.e the ester group adjacent to the ethylhexane side chain, and the ester group at the opposite end of the molecules. The carbon range in the main backbone of the molecules is all the same (C18) though the acetate moiety is attached at slightly different positions (C12 for BT4, C9/10 for the analogue diesters). The analogue diesters have the additional alkane chain attached to the acetate cap. The alkane chains themselves are not typically considered to be functional groups, per se, as they are relatively inactive biologically. Thus the parent molecules BT4 and the analogue diesters are similar enough to allow for read across in that there are no differences with respect to functional groups, and their only real difference is number of, and length of, saturated hydrocarbon chains.

The adsorption coefficient (Koc) of the test item SE7B has been determined to be greater than 4.27 x 10^5, greater than log₁₀Koc 5.63. These values indicate that the test item and BT4 will be immobile in the environment.

Reference 2

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

10 March 2015 - 30 March 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

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

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:

other: HPLC method

Specific details on test material used for the study:

Identification: SE7B
Appearance/Physical State: Clear colorless liquid
Batch: 0000140602
Expiry Date: 18 February 2017
Storage Conditions: Room temperature in the dark

Radiolabelling:

no

Test temperature:

Column temperature : 40ºC

Details on study design: HPLC method:

Test System
The determination was carried out using the HPLC screening method, designed to be compatible with Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001.
The test system utilized a high performance liquid chromatograph. A commercially available cyanopropyl reverse phase HPLC column containing lipophilic and polar moieties was used.

Performance of the Test
-Preparation of sample solution
Test item (0.1514 g) was diluted to 100 mL with acetonitrile to give a concentration of 1.514 g/L.
-Preparation of dead time solution
The dead time was determined by measuring the retention time of formamide (purity 99.94%, 644 mg/L solution in 55:45 acetonitrile: purified water).
-Preparation of reference standard solutions
Solutions of reference standards (see the table) were prepared in methanol.

Determination of retention time
The sample, dead time and reference standard solutions were injected in duplicate using the following HPLC parameters:
HPLC System :
- Agilent Technologies 1200 series, incorporating autosampler and workstation
- Polymer Laboratories Evaporative Light Scattering Detector 1000 (ELSD)
Column :
- Waters XSelect HSS Cyano 5mm (150 x 4.6 mm id)
Column temperature :
- 40ºC
Mobile phase :
- 55:45 v/v Acetonitrile: purified water 100% Acetonitrile post 15 minutes (after DDT peak elution) pH of mobile phase : 8.18
Flow-rate :
- 1.0 mL/min
Injection volume :
- 10 μl (samples)
- 100 mL (standards)
UV detector wavelength (standards) :
- dead time and reference standards: 210 nm
ELS detector (samples) :
- Evap temperature : 80 °C
- Nebulizer temperature: 40 °C
- Gas flow: 1.0 mL /min

Calculation
Construction of calibration curve
A calibration curve was constructed from the retention time data of the dead time and reference standard solutions. The capacity factors k' for the reference standards were calculated using the equation below.

Adsorption coefficient of sample
The capacity factor was calculated using the following equation:
k' = ( tr – t₀ ) / t₀
where:
k' = capacity factor
tr = retention time (min)
t₀ = dead time (min)

and the log₁₀Koc value determined using the following equation with reference to the calibration curve.
Log₁₀ Koc = ( log₁₀ k' – A ) / B
where:
Koc = adsorption coefficient
k' = capacity factor
A = intercept of the calibration curve
B = slope of the calibration curve

A correlation of log k' versus log Koc of the calibration standards was plotted using linear regression.

The mobility classification of the test item was obtained by comparing the calculated Koc value to the mobility classes according to P.J. McCall, R.L. Swann, D.A. Laskowski, S.M. Unger, S.A. Vrona and H.J. Dishburger “Estimation of Chemical Mobility in Soil from Liquid Chromatography Retention Times”; Bull. Environm. Contam. Toxicol. 24, 190-195 (1980).

Range of Koc // Mobility Class
0-50 = Very high
50-150 = High
150-500 = Medium
500-2000 = Low
2000-5000 = Slightly
>5000 = Immobile

Analytical monitoring:

not specified

Key result

Sample No.:

#1

Type:

log Koc

Value:

> 5.63 dimensionless

pH:

8.18

Temp.:

40 °C

Sample No.:

#1

Type:

Koc

Value:

> 427 000 dimensionless

Details on results (HPLC method):

Adsorption coefficient of sample
The retention times, capacity factor and log10 Koc value determined for the sample are shown in the table below.
Overall log10 Koc: >5.63
Adsorption coefficient: >4.27 x 10^5

Discussion
As the test item had a high affinity for the stationary phase of the column, the mobile phase was adjusted to 100% acetonitrile shortly after the retention time of DDT to elute the sample. All peaks for the test item eluted after the adjustment to 100% acetonitrile, therefore the test item adsorption coefficient has been quoted as greater than DDT.
The test item has a very low solubility in methanol and water, therefore acetonitrile was chosen as a suitable organic solvent for the mobile phase in order to maintain solubility of the test item.
As the slope of the calibration curve for the reference standards showed good first order correlation and as the retention times between duplicate injections for each solution was consistent, the HPLC method was considered valid for the determination of adsorption coefficient. Based on the chromatographic data, the test item was considered to be stable during the test procedure as there was no shift in retention time.

Conclusion
The adsorption coefficient (Koc) of the test item has been determined to be greater than 5.63, greater than log₁₀Koc 4.27 x 10^5. These values indicate that the test item will be immobile in the environment.

Adsorption coefficient of sample

Peak	Injection	Retention Time (mins)	Capacity Factor (k')	Log10K'	Log10Koc	Mean Log10Koc	Adsorption Coefficient
TI	1	16.517	8.38	0.923	>5.63	>5.63	>4.27 x 10^5
TI	2	16.517	8.38	0.923	>5.63
TI2	1	16.683	8.47	0.928	>5.63	>5.63	>4.27 x 10^5
TI2	2	16.683	8.47	0.928	>5.63

Validity criteria fulfilled:

yes

Conclusions:

The adsorption coefficient (Koc) of the test item has been determined to be greater than 4.27 x 10^5, greater than log₁₀Koc 5.63. These values indicate that the test item will be immobile in the environment.

Additional information

Read-Across is claimed between BT4 (target) and SE7B (Source), according to the justification attached to the target record, and based on structural and physical/chemical similarities.

Analogue diesters (SE7B, SE6B) and BT4 contain the same functional groups, i.e the ester group adjacent to the ethylhexane side chain, and the ester group at the opposite end of the molecules. The carbon range in the main backbone of the molecules is all the same (C18) though the acetate moiety is attached at slightly different positions (C12 for BT4, C9/10 for the analogue diesters). The analogue diesters have the additional alkane chain attached to the acetate cap. The alkane chains themselves are not typically considered to be functional groups, per se, as they are relatively inactive biologically. Thus the parent molecules BT4 and the analogue diesters are similar enough to allow for read across in that there are no differences with respect to functional groups, and their only real difference is number of, and length of, saturated hydrocarbon chains.

The adsorption coefficient (Koc) of the test item SE7B has been determined to be greater than 4.27 x 10^5, greater than log₁₀Koc 5.63. These values indicate that the test item and BT4 will be immobile in the environment.