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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
Justification for type of information:
Data is from experimental study performed using standard OECD Guideline
Qualifier:
according to
Guideline:
OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))
Principles of method if other than guideline:
To determine Adsorption coefficient (KOC) on soil and on sewage sludge of the test chemical using HPLC.
GLP compliance:
no
Type of method:
HPLC estimation method
Media:
soil/sewage sludge
Specific details on test material used for the study:
- Name of test material : Ethyl butyrate
- Molecular formula: C6H12O2
- Molecular weight: 116.1588 g/mol
- SMILES: C(=O)(CCC)OCC
- InChI: 1S/C6H12O2/c1-3-5-6(7)8-4-2/h3-5H2,1-2H3
- Substance type: Organic
- Physical state: Liquid
- Batch no.: 0001
- Purity: 98.04%
- Physical Appearance: colorless liquid
- Stability: Stable in recommended storage conditions
- Storage Conditions: 1. Ambient Temp (23 to 27 °C) (Keep container tightly closed in a dry & well-ventilated place. Store in cool place. Do not expose to air, light & moisture.)
Radiolabelling:
not specified
Test temperature:
25°C
Details on study design: HPLC method:
HPLC Procedure:
The solutions of the test substance and reference substances were prepared in solvent mentioned in 4.3. Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(table 3).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor.

Operating Conditions:
HPLC Model No. : Agilent Technologies,1260 Infinity
Flow Rate : 1.0ml/min
Column : ZORBAX Eclipse Plus C18, 4.6×100mm, 3.5 μm
Mobile phase : ACN : water (55:45)
Temperature : 25°C
Detector : Diode Array Detector @210nm
Injector : Autosampler
Injector volume : 10μl
Data Acquisition software : ChemStationOpen lab Control Panel
Analytical monitoring:
not specified
Details on sampling:
- Concentrations: 349.4 mg/l
- Sampling interval: A test item solution was prepared by accurately measuring 4μL of test item and diluted with methanol up to 10ml. Thus, the test solution concentration was 349.4 mg/l. The pH of test substance was 6.68.
Key result
Type:
log Koc
Value:
1.346 dimensionless
pH:
6.68
Temp.:
25 °C
Remarks on result:
other: LogKoc was reported to be 1.3463 ± 0.002
Details on results (HPLC method):
The Adsorption coefficient (KOC) on soil and on sewage sludge of the test chemical was determined to be 1.3463 ± 0.002 at 25°C
Transformation products:
not specified

Test substance

K

Log k

Log Koc

by Generalized Calibration

Graph

Mean of Log Koc ± S.D.

tR1

4.169

3.3068

0.5194

1.3451

1.3463 ± 0.002

tR2

4.194

3.3326

0.5227

1.3473

Validity criteria fulfilled:
yes
Conclusions:
The Adsorption Coefficient of test chemical was determined as per the HPLC method (OECD Guideline-121). The Log Koc value was determined to be 1.3463 ± 0.002 at 25°C.
Executive summary:

The adsorption coefficient Koc in soil and in sewage sludge of test chemical was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals. The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately measuring 4μL of test item and diluted with methanol up to 10ml. Thus, the test solution concentration was 349.4 mg/l. The pH of test substance was 6.68. Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor. The reference substances were chosen according to functional group similarity with the test substance and calibration graph prepared. The reference substances were 2 -nitrophenol, nitrobenzene, 4-nitrobenzamide, N,N-dimethylbenzamide, N-methylbenzamide, benzamide having Koc value ranging from 1.239 to 2.47. The Log Koc value of test chemical was determined to be 1.3463 ± 0.002 at 25°C. This log Koc value indicates that the test chemical has a negligible sorption to soil and sediment and therefore have rapid migration potential to ground water.

Description of key information

The adsorption coefficient Koc in soil and in sewage sludge of test chemical was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals (Experimental study report, 2017). The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately measuring 4μL of test item and diluted with methanol up to 10ml. Thus, the test solution concentration was 349.4 mg/l. The pH of test substance was 6.68. Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor. The reference substances were chosen according to functional group similarity with the test substance and calibration graph prepared. The reference substances were 2 -nitrophenol, nitrobenzene, 4-nitrobenzamide, N,N-dimethylbenzamide, N-methylbenzamide, benzamide having Koc value ranging from 1.239 to 2.47. The Log Koc value of test chemical was determined to be 1.3463 ± 0.002 at 25°C. This log Koc value indicates that the test chemical has a negligible sorption to soil and sediment and therefore have rapid migration potential to ground water.

Key value for chemical safety assessment

Koc at 20 °C:
22.181

Additional information

Various experimental key and supporting studies for the test chemical were reviewed for the adsorption end point which are summarized as below:

 

In an experimental key study from study report (2017), the adsorption coefficient Koc in soil and in sewage sludge of test chemical was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals. The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately measuring 4μL of test item and diluted with methanol up to 10ml. Thus, the test solution concentration was 349.4 mg/l. The pH of test substance was 6.68. Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor. The reference substances were chosen according to functional group similarity with the test substance and calibration graph prepared. The reference substances were 2 -nitrophenol, nitrobenzene, 4-nitrobenzamide, N,N-dimethylbenzamide, N-methylbenzamide, benzamide having Koc value ranging from 1.239 to 2.47. The Log Koc value of test chemical was determined to be 1.3463 ± 0.002 at 25°C. This log Koc value indicates that the test chemical has a negligible sorption to soil and sediment and therefore have rapid migration potential to ground water.

 

Another adsorption study was conducted for estimating the adsorption coefficient (Koc) value of test chemical (authoritative databases HSDB and PubChem, 2017). The adsorption coefficient (Koc) value was calculated using a structure estimation method based on molecular connectivity indices. The adsorption coefficient (Koc) value of test substance was estimated to be 20 (Log Koc = 1.3). This Koc value indicates that the test chemical has a negligible sorption to soil and sediment and therefore have rapid migration potential to ground water.

 

For the test chemical, adsorption study in soil was conducted for determining the adsorption coefficient (Koc) value of test chemical (handbook, 2008). The adsorption coefficient (Koc) value of test substance was calculated to be 41 (Log Koc = 1.612). This Koc value indicates that the test substance has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.

 

In an another study from peer reviewed journal (Lambri M. et. al., 2013), adsorption experiment was conducted for evaluating the adsorption capacity of test chemical onto bentonite clay. The study was performed using thebatch equilibrium method. A buffer solution containing 6 g/L tartaric acid adjusted to pH 3.30 with 1N potassium hydroxide and supplemented with 13% ethanol (v/v) was prepared. For test chemical, a defined volume of 1000 mg/l stock solution was prepared in absolute ethanol and stored at -28°C until use. An aliquot was added to a defined volume of the buffer solution to obtain a test chemical conc. used of 4 mg/l (4000 µg/l). Three samples of natural Ca2+-bentonite activated with Na+ were purchased from Dal Cin Gildo (Concorezzo,Italy).Two of the samples were powdery clays (A and C) and one of the samples was a granular bentonite (B). The A and B samples came from the same raw montmorillonite and the C bentonite originated from a montmorillonite containing magnesium smectite. Each bentonite sample was used in three different concentrations (0.2, 0.5 and 1 g/L) to treat the model wine solution. The bentonites were rehydrated in deionized water at a bentonite: water ratio of 10:100 (w/w). For each concentration of bentonite sample, three replicates were prepared in order to arrange three adsorption independent experiments. After the 90 mins of bentonites rehydration, the resulting slurries were stirred. Each suspension was then added to glass conical flasks containing 500 mL of the test chemical solution and thoroughly mixed for 90 s.A sample of the test chemical solution without any addition of bentonite was treated under the same conditions and kept in triplicate as a control test. The glass stoppered flasks (samples and control test) were then placed in a 60% relative humidity incubator at 17±1°C in static conditions to simulate the sedimentation. After 24 hours, the limpid liquid phases of both samples and control test were separated and filtered through folded filters (595 ½, Whatman GmbH, Germany).The adsorption data were expressed by the Langmuir and Freundlich models. To ensure equilibrium, the concentration of the adsorbate was measured after 12, 24 and 36 hours of contact time between the model wine solution and the bentonite. As there was no further increase in adsorption past the 24-hour mark, a contact time of 24 hours was established as the equilibrium time.The data were analyzed using the statistics package IBM SPSS Statistics 19 (IBM Corporation, New York, USA). The bentonite characteristics and the data from the odor-active compound analysis were analyzed by a factorial ANOVA. Significant differences were also analyzed using Tukey’s test atp≤ 0.05. The data from the batch adsorption experiments were analyzed by the curve estimation procedure. This procedure is the most appropriate when the relationship between the dependent variable(s) and the independent variable is not necessarily linear and generates for each dependent variable the related plots for 11 different curve estimation regression models. Finally, the risk (error onr2) and the prediction ability of the best models selected from curve estimation procedure were evaluated by cross validation (CV).The Langmuir adsorption isotherms constants (KL) at 17±1°C was determined to be -0.56, 0.07 and -0.04 and the Freundlich adsorption constants (KF) was determined to be 0.01, 3.66 and 0.47 on bentonite clay A, B and C, respectively. Thus, based on this, it can be concluded that the test chemical has a negligible to low sorption to soil and sediment and therefore have rapid to moderate migration potential to ground water.

 

On the basis of above overall results for test chemical (from study report, handbook, authoritative database and peer reviewed journal,2017), it can be concluded that the logKoc value of test chemical was determined to be ranges from 1.3 to 1.612, respectively, indicating that the test chemical has a negligible to low sorption to soil and sediment and therefore have rapid to moderate migration potential to ground water.

[LogKoc: 1.346]