Dihexyl ether

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

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

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Media:

soil/sewage sludge

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: 05079/MA
- Expiration date of the lot/batch: 04/2020

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: No special storage conditions required (stable at normal ambient temperature and normal pressure.

Radiolabelling:

no

Test temperature:

23.2-23.7°C (mean 23.5°C)

Details on study design: HPLC method:

EQUIPMENT
- Type: HPLC
- Column: YMC-Pack Cyano / S-5 pm / 12 nm, 250 x 4.0 mm, batch 13303,YMC Europe GmbH
- Detection system: GC-MS

MOBILE PHASES
- Type: Acetonitrile : ultrapure water (70 : 30)

DETERMINATION OF DEAD TIME
- Method: Sodium nitrate was used for determination of the dead time of the test system (threefold injection of 5 mg/l).

REFERENCE SUBSTANCES
- Identity: Sodium nitrate, Acetanilide, Atrazine, 4-Nitrobenzamide, Monuron, Linuron, Phenyl benzoate, Fenthion, Phenantrene, 44,-DDT

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 1 g/L
- Quantity of reference substances: 20 mg/L for 4,4-DDT and Endosulfan-diol, 5 mg/L for the others

REPETITIONS
- Number of determinations: 3

EVALUATION
- Calculation of capacity factors k': k'=(tR-t0)/t0 (tR- retention time, t0-dead time)
- Calculation of retention times: The mean retention time for each fraction was calculated and multiplied with the corresponding HPLC or GC areas, summed up and divided by the sum of the HPLC or GC areas. This weighted mean value was the retention time tR for the further calculation.
- Determination of the log Koc value: By linear regression of the log Koc of the reference items against the log k' of the reference items the equation for the calibration graph was obtained.

Key result

Type:

log Koc

Value:

4.3 dimensionless

Temp.:

23.5 °C

Matrix:

soil

Type:

log Koc

Value:

4.4 dimensionless

Temp.:

23.5 °C

Matrix:

sewage sludge

Remarks on result:

other: extrapolated

Details on results (HPLC method):

see Table (Results for the Reference Items for Soil and Sewage Sludge) below

Calibration of the Reference Items for Soil and Sewage Sludge

Reference item	log Koc (soil)	log Koc (sewage sludge)	1st calibration			2nd calibration
			tR1 [min]	k'	log k'	tR2 [min]	k'	log k'
Acetanilide	1.26	1.52	2.747	0.83	-0.0830	2.767	0.84	-0.0761
Atrazine	1.81	1.66	2.828	0.88	-0.0556	2.793	0.86	-0.0672
4 -Nitrobenzamide	1.93	1.52	2.672	0.78	-0.1100	2.708	0.80	-0.0968
Monuron	1.99	1.46	2.772	0.84	-0.0743	2.783	0.85	-0.0706
Linuron	2.59	2.43	2.925	0.94	-0.0249	2.920	0.94	-0.0264
Phenyl benzoate	2.87	3.26	2.991	0.99	-0.0051	2.990	0.99	-0.0054
Fenthion*	3.31	3.75	2.966	0.97	-0.0125	3.055	1.03	0.0132
Phenanthrene	4.09	4.35	3.158	1.10	0.0411	3.171	1.11	0.0445
4,4'-DDT	5.63	-	3.392	1.25	0.0986	3.364	1.24	0.0921

Validity criteria fulfilled:

yes

Conclusions:

The log Koc value for soil was determined to be 4.3. For sewage sludge the test item eluted slightly after the reference item with the highest log Koc value (phenanthrene). Therefore, the log Koc value was extrapolated and estimated to be 4.4 for sewage sludge.

Executive summary:

The adsorption coefficient (Koc) for the test item Dihexyl ether on soil and on sewage sludge using high performance liquid chromatography (HPLC) was estimated according to OECD 121 (2001) and Council Regulation (EC) No. 440/2008, Method C.19.

The HPLC eluent was fractionated by a liquid handler. Fractions for the detection of the test item were analysed by GC-MS. Fractions for the detection of the reference items were analysed by HPLC-DAD. Reconstructed chromatograms were derived for the test item and the reference items followed by further data assessment and calculation of the study endpoints (log Koc for soil and sewage sludge).

Calibrations were performed using eight reference items for soil and six reference items for sewage sludge with known log Koc values (according to the guideline). The reference items were measured twice, once before and once after the measurement (double injection of one replicate) of the test item (single injection of three replicates). Sodium nitrate was used for determination of dead time of the test system.

The log Koc value for soil was determined to be 4.3. For sewage sludge the test item eluted slightly after the reference item with the highest log Koc value (phenanthrene). Therefore, the log Koc value was extrapolated and estimated to be 4.4 for sewage sludge.

Description of key information

 The log Koc value for soil was experimentally determined in an OECD 121 study to be 4.3. For sewage sludge the log Koc value had to be extrapolated and was estimated to be 4.4.

Key value for chemical safety assessment

Koc at 20 °C:

19 953

Additional information

Supporting the experimental finding, the adsorption coefficient log Koc of the substance was calculated to be 3.07 (from Molecular Connectivity Index) and 3.59 (calculated from Log Kow).