Tetrakis(2-ethylhexyl) benzene-1,2,4,5-tetracarboxylate

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018-01-02 - 2018-01-28

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))

Version / remarks:

January 22, 2001

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))

Version / remarks:

March 04, 2016

Deviations:

no

GLP compliance:

yes

Type of method:

HPLC estimation method

Media:

other: not applicable

Radiolabelling:

no

Test temperature:

35°C +/- 1°C (column temperature)

Details on study design: HPLC method:

Performance of the study
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. Therefore, the pKa values of the test item 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 method was performed at neutral pH.

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.

Preparation of Solutions
Reference Substance Solution
A stock solutions of the 4,4’-DDT (98.7%, [50-29-3], Sigma-Aldrich, Steinheim, Germany) at a concentration 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/water.
The blank solution for the reference substance was 55/45 (v/v) methanol/water.
Test Solution
A 1000 mg/L stock solution of the test item was prepared in methanol. The solution was ultrasonicated for 3 minutes. The stock solution was 100 fold diluted with 55/45 (v/v) methanol/water. The final concentration of the test item solution was 10 mg/L.
The test item blank solution was 55/45 (v/v) methanol/water.

Analytical Method:
Conditions:
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

Mobile phase
Solvent A Methanol
Solvent B Water
Gradient refer to "Any other details on materials and methods" (A gradient was applied in order to elute components with log Koc > 5.63 from the column. The reference compounds are eluted in the isocratic part of the method and the gradient step was not applied for these injections.)
Flow: 0.4 mL/min
UV detection: 210 nm

Sample Injections
Reference substance and test item solutions were injected in duplicate. Blank solutions were analyzed by single injection.

Key result

Type:

log Koc

Value:

> 5.63 dimensionless

pH:

7

Temp.:

35 °C

Type:

Koc

Value:

> 427 000 dimensionless

pH:

7

Temp.:

35 °C

Details on results (HPLC method):

pKa Values
No pKa values for acidic and basic groups in the molecular structure of the test item in the logarithm range of 1 - 14 were calculated.

Koc HPLC Method
UPLC-UV chromatograms of the test item solution and the corresponding blank are shown in Figure 1 and Figure 2 of the study report, respectively. In the chromatogram of the test item solution, one peak with a retention time of 6.4 minutes was observed. Under the same analytical conditions, the retention time of 4,4’-DDT (log Koc = 5.63) was 4.7 minutes. It was concluded that the log Koc of test item was > 5.63 (Koc > 4.27 x 10E5).

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 test substance.
The Koc and log Koc values of the test item at neutral pH are:
Koc > 4.27 x 10E5
log Koc > 5.63

Executive summary:

The objective of this study was to estimate the adsorption coefficient (Koc) using high performance liquid chromatography (HPLC). The test was conducted according to EC Guideline C.19 and to OECD Guideline 121 in compliance with GLP. The HPLC method was performed at neutral pH. Solutions of the reference substance DDT (CAS 50 -29 -3) based on soil adsorption data and the test item were analyzed. Reference substance and test item solutions were injected in duplicate while blank solutions were analyzed by single injection. Based on the retention times of the compounds the Koc and log Koc values of the test item were determined.

In the chromatogram of the test item solution, one peak with a retention time of 6.4 minutes was observed. Under the same analytical conditions, the retention time of DDT (log Koc = 5.63) was 4.7 minutes. It was concluded that the log Koc of the test item at neutral pH and at a test temperature of 35°C is > 5.63 (Koc > 4.27 x 10E5).

Description of key information

The objective of this study was to estimate the adsorption coefficient (Koc) using high performance liquid chromatography (HPLC). The test was conducted according to EC Guideline C.19 and to OECD Guideline 121 in compliance with GLP. The HPLC method was performed at neutral pH. Solutions of the reference substance DDT (CAS 50 -29 -3) based on soil adsorption data and the test item were analyzed. Reference substance and test item solutions were injected in duplicate while blank solutions were analyzed by single injection. Based on the retention times of the compounds the Koc and log Koc values of the test item were determined.

In the chromatogram of the test item solution, one peak with a retention time of 6.4 minutes was observed. Under the same analytical conditions, the retention time of DDT (log Koc = 5.63) was 4.7 minutes. It was concluded that the log Koc of the test item at neutral pH and at a test temperature of 35°C is > 5.63 (Koc > 4.27 x 10E5).

Key value for chemical safety assessment

Koc at 20 °C:

427 000

Additional information

The reported "Key value for chemical safety assessment" was determined at a higher temperature (35 °C). Furthermore, the value should be considered with caution since it is an estimated value. The actual Koc value of the test item is greater than the indicated (minimum) value.

(Reliable) supporting QSARs for tetrakis(2-ethylhexyl) benzene-1,2,4,5-tetracarboxylate

The estimated soil adsorption coefficient Log Koc using MCI model from EPI Suite Software v4.1 is 10.58

The estimated soil adsorption coefficient Log Koc using Log Kow model from EPI Suite Software v4.1 is 4.12

According to the McCall classification scheme of soil mobility potential, Log Koc above 8.97 means the substance is immobile in soil.

[LogKoc: 10.58]