Hexanoic acid, 2-ethyl-, C12-15-alkyl esters

Adsorption / desorption

Administrative data

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

29 Dec 2017 - 9 Feb 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

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))

Version / remarks:

22 January 2001

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))

Version / remarks:

4 March 2016

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: EC Technical Guidance Document on Risk Assessment Part III Chapter 4.3: Use of (Quantitative) Structure Activity Relationships ((Q)SARs) - Soil and Sediment Sorption.

Version / remarks:

2003

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Media:

soil

Test material

Test material information

Constituent 1

Reference substance name:

Hexanoic acid, 2-ethyl-, C12-15-alkyl esters

EC Number:

291-443-0

EC Name:

Hexanoic acid, 2-ethyl-, C12-15-alkyl esters

Cas Number:

90411-66-8

IUPAC Name:

Hexanoic acid, 2-ethyl-, C12-15-alkyl esters

Test material form:

liquid

Radiolabelling:

no

Study design

Test temperature:

35°C ± 1°C

HPLC method

Details on study design: HPLC method:

EQUIPMENT
- Instrument: Acquity UPLC system (Waters, Milford, MA, USA)
- Detector: Acquity UPLC TUV detector (Waters)
- Column: Acquity UPLC HSS Cyano, 100 mm x 2.1 mm i.d., dp = 1.8 µm (Waters)
- Column temperature: 35°C ± 1°C
- Injection volume: 5 µL
- Solvent A: methanol
- Solvent B: Phosphate buffer pH 7, 0.01 M
- Gradient: see below.
- Flow: 0.4 mL/min
- UV detection: 210 nm

MOBILE PHASES
- Reference Substance Solution with log Koc 5.63:
A stock solution of 4,4’-DDT (98.7%, [50-29-3], Sigma-Aldrich, Steinheim, Germany) at concentrations of approximately 1 g/L in methanol was used. The stock solution was diluted to obtain an end solution of 55/45 (v/v) methanol/buffer pH 7.
The blank solution for the mixture of reference substances was 55/45 (v/v) methanol/
buffer pH 7.
- Test Solution:
A 1000 mg/L stock solution of the test item was prepared in methanol. The stock solution was 10 fold diluted to 55/45 (v/v) methanol/buffer pH 7. The final concentration of the test item solution was 100 mg/L.
The test item blank solution was 55/45 (v/v) methanol/buffer pH 7.
- Sample Injections:
Reference substance and test item solutions were injected in duplicate. Blank solutions were analyzed by single injection.

REFERENCE SUBSTANCES
- Identity: 4,4’-DDT (98.7%, [50-29-3], Sigma-Aldrich, Steinheim, Germany)

REPETITIONS
- Number of determinations: 2

PERFORMANCE AND EVALUATION
The principle of the test method is similar to that of the OECD guideline no. 117: "Partition coefficient (n-octanol/water), high performance liquid chromatography (HPLC) method". While passing through the column along with the mobile phase the test item interacts with the stationary phase. As a result of partitioning between mobile and stationary phases, the test item is retarded. The dual composition of a cyanopropyl stationary phase, having polar and non-polar sites allows for interaction of polar and non-polar groups of a molecule in a similar way as is the case for organic matter in soil or sewage sludge matrices. This enables the relationship between the retention time on the column and the Koc on organic matter to be established.
According to the guidelines, the determination of the Koc for test items 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. Because the test item is a mixture, the pKa values of the test item could not be calculated using the Perrin calculation method (pKalc 5.0, module in Pallas 3.0, CompuDrug International San Francisco, CA, USA). Therefore, it was decided to perform the test at pH 7.
Solutions of one reference substance based on soil adsorption data and the test item were analyzed. Based on the retention times of the compounds the Koc and log Koc values of the test item were determined.

Results and discussion

Adsorption coefficient

Adsorption coefficient 1

Sample No.:

#1

Type:

log Koc

Value:

> 5.63 dimensionless

pH:

7

Temp.:

35 °C

Adsorption coefficient 2

Sample No.:

#2

Type:

log Koc

Value:

> 5.63 dimensionless

pH:

7

Temp.:

35 °C

Results: HPLC method

Details on results (HPLC method):

UPLC-UV chromatograms of the test item solution and the corresponding blank are shown in Figure 6 and Figure 7, respectively. In the chromatogram of the test item solution, five peaks with a retention time of 20.9, 21.7, 21.8, 22.6 and 23.2 minutes were observed. Under the same analytical conditions, the retention time of 4,4’-DDT (log Koc = 5.63) was 5.6 minutes. It was concluded that the log Koc of test item was > 5.63 (Koc > 4.3 E10+5).

Any other information on results incl. tables

pH 7: K_oc of the Test Item

Substance	Retention time (min)			log Koc	Koc
	tr,1	tr,2	mean
4,4’-DDT	5.638	5.663	5.651	5.63
209079 – peak 1	20.852	20.871	20.862	> 5.63	> 4.3´10^5
209079 – peak 2	21.694	21.698	21.696	> 5.63	> 4.3´10^5
209079 – peak 3	21.831	21.834	21.833	> 5.63	> 4.3´10^5
209079 – peak 4	22.584	22.559	22.572	> 5.63	> 4.3´10^5
209079 – peak 5	23.151	23.15	23.151	> 5.63	> 4.3´10^5a

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The log Koc of the test material was determined to be >5.63 at pH 7 and 35 °C under the conditions of the test.

Executive summary:

In this guideline (OECD 121) study the adsoprtion coefficient of the test material (EC 291-443-0) was determined to be log K_oc >5.63 at pH 7 and 35 °C. The test was conducted using the HPLC estimation methodology.