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Endpoint:
adsorption / desorption, other
Adequacy of study:
supporting study
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: The result is sourced from secondary literature. The original reference, with original Koc measurement work, was not available for review and no further information is available.
Type:
log Koc
Value:
2.59
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
December 2013
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to an appropriate OECD test guideline. However, no purity data, no pH data, no temperature data and no information on repeatability (number of duplicates) were reported.
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))
GLP compliance:
no
Remarks:
however the study was covered by ISO 17025 certification
Type of method:
HPLC estimation method
Media:
soil/sewage sludge
Radiolabelling:
no
Details on study design: HPLC method:
EQUIPMENT
- Apparatus: Agilent 1200 pump, autosampler, and refractive index detector with an EZChrom Elite data system.
- Type:
- Type, material and dimension of analytical (guard) column: Discovery® Cyano 5 µm 250 mm x 4.6 mm analytical column maintained at 40˚C with a 5μm Discovery® Cyano Supelguard™ Cartridge 20 mm × 4.0 mm guard column positioned between the injection system and the analytical column.
- Detection system: Refractive index detection.

MOBILE PHASES
- Type:
- Experiments with additives carried out on separate columns: yes / no: not reported.
- pH: Not reported.
- Solutes for dissolving test and reference substances: methanol.

DETERMINATION OF DEAD TIME
- Method: by inert substances which are not retained by the column (formamide).

REFERENCE SUBSTANCES
- Identity: Phenol, Methyl benzoate, 3,5-Dinitrobenzamide, Naphthalene, 1,2,3-Trichlorobenzene and DDT.

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 5 µl: Test and reference samples were prepared with 0.05 g of test substance in 25 ml of methanol. 5 µl of sample were injected with a flow rate of 1 ml min-1 and a mobile phase of 55% (v/v) methanol and water.
- Quantity of reference substances: 5 µl.
- Intervals of calibration: Not reported.

REPETITIONS
- Number of determinations: Not reported.

EVALUATION
- Calculation of capacity factors k': capacity factor, k, where k = (tr – t0)/t0
- Calculation of retention times: The retention time was determined for each of the reference and test substances, tr, in relation to that of the unretained solute, formamide, t0.
- Determination of the log Koc value: The retention times for a series of reference compounds were determined to form a correlation plot for the calculation of the log organic carbon-water adsorption coefficient for test substances. Linear regression of the organic carbon-water adsorption coefficient (log Koc) of reference substances against the log of capacity factors (log k) of the reference substances determines the linear regression coefficients (a and b). The organic carbon-water adsorption coefficient of a test substance can be calculated by inserting its experimentally determined capacity factor into the below equation:
Log Koc = a + b log k
Type:
log Koc
Value:
2.9
Remarks on result:
other: 1-decanol
Type:
Koc
Value:
802
Remarks on result:
other: 1-decanol
Details on results (HPLC method):
- Retention times of reference substances used for calibration: normal (refer to Table 1 below).
- Details of fitted regression line (log k' vs. log Koc): The data demonstrate a good correlation (R2 = 0.9907) between the experimentally derived capacity factor (k) and the literature log Koc values for the reference substances.
- Average retention data for test substance: mean retention time 5.58 min; log k = -0.21; Koc 802, log Koc 2.90.

Table 1. Comparison of experimentally determined log k and literature log Kocvalues for the reference substances

Substance

Mean retention time (tr) (min)

Log k
(log(tr-t0/t­0))

Literature log Koc

Phenol

 

4.26

1.27

1.32

Methyl benzoate

4.50

1.70

1.80

 

3,5-Dinitrobenzamide

4.88

2.23

 

2.31

 

Naphthalene

 

5.58

 

2.90

 

2.75

 

1,2,3-Trichlorobenzene

 

6.27

 

3.37

 

3.16

 

DDT

13.44

5.49

5.63

Table 2. HPLC-derivedlog Kocvalues for the range of alcohol test substances

Test substances (alcohols)

Mean retention time (tr) (min)

Log k
(log(tr-t0/t0))

Koc

Log Koc

1-hexanol

4.25

-0.64

17.9

1.25

1-heptanol

4.48

-0.53

47.3

1.68

1-octanol

4.77

-0.43

123

2.09

1-nonanol

4.96

-0.36

211

2.32

1-decanol

5.58

-0.21

802

2.90

1-undecanol

6.15

-0.11

2006

3.30

1-dodecanol

6.89

0.00

5098

3.71

1-tridecanol

7.85

0.10

13149

4.12

1-tetradecanol

9.08

0.21

33983

4.53

1-pentadecanol

10.69

0.32

89883

4.95

1-hexadecanol

12.89

0.43

249732

5.40

Table 3. Experimentally derived log Kocvalues for the test substances, comparison of HPLC and adsorption study results

Compound

Koc

Log Koc

Log Koc

Difference

Possible Correction factor1

Previous experimental data

HPLC

1-hexanol

10.2

1.012

1.25

-0.24

 

 

0.17+0.74

1-dodecanol

17980

4.253

3.71

0.55

1-tridecanol

50830

4.713

4.12

0.59

1-hexadecanol

143000

5.153

5.40

-0.24

1 = mean difference between the methods

2 = Gerstl and Helling (1987)

3 = van Compernolle et al. (2006)

Validity criteria fulfilled:
yes
Conclusions:
An adsorption coefficient (Koc) value of 802 (log Koc 2.9) was determined in a reliable study conducted according to an appropriate test protocol (OECD 121).
Endpoint:
adsorption / desorption, other
Remarks:
adsorption
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Remarks:
The result was obtained by the valid application of a well-established predictive method.
Justification for type of information:
Please refer to the associated QMRF and QPRF for details of the model validation, input parameters and other remarks. QSAR validation for this endpoint is discussed further in the Alcohols Environmental Fate Category Report.
Principles of method if other than guideline:
The result was obtained using an appropriate QSAR method.
GLP compliance:
no
Media:
soil
Type:
Koc
Value:
6 330 L/kg
Conclusions:
A Koc value of 6330 was obtained using an accepted calculation method. The result is considered to be reliable.
Endpoint:
adsorption / desorption, other
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted in compliance with standard guideline and with GLP, all validity criteria met.
Qualifier:
according to guideline
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Version / remarks:
(2000)
GLP compliance:
yes
Type of method:
batch equilibrium method
Media:
other: Four standard soils and also activated sludge solids
Radiolabelling:
yes
Test temperature:
19.1 - 21.6ºC
Analytical monitoring:
yes
Details on sampling:
- Concentrations:Adsorption isotherms of decanol were estimated in the range of initial decanol concentrations in the solutions from 1 – 2 μg L-1 to approximately 104 - 105 μg L-1.
- Sampling interval: 1 h, 2 h, 4 h, 24 h
- Sample storage before analysis: not reported
Details on matrix:
Soil collection and characterisation details are presented in Tables 1-2 below.

Activated sludge solids:
- Type of sludge: Activated sludge
- Source of sludge: Denton Wastewater Treatment Plant (WWTP), Denton, MD, USA
- Oxygen status: not reported but presumed to be aerobic
- Laboratory culture: not applicable
- Method of cultivation: not applicable
- Pretreatment: The activated sludge was sieved through a 2-mm screen and allowed to settle for approximately 1 hour. The supernatant was removed and the remaining sludge solids were washed with deionized water. Washing was accomplished by adding de-ionized water to the residue in the container and suspending the sludge solid in the water followed by settling for approximately 1 hour and removal of the supernatant. Sludge solids were washed three times and then centrifuged at Relative Centrifugal Force (RCF) approximately 1900 g for 5 minutes at ambient room temperature. The supernatant was decanted and discarded.
- Initial cell/biomass concentration: not reported

PREPARATION OF SLUDGE SOLIDS
The washed sludge solids (see above) were frozen at approximately –80ºC prior to freeze-drying (lyophilization). After lyophilization, the solids were broken into a dry powder by passing through a 2-mm screen. The powder was heated (desiccated) at approximately 103ºC for 3 hours prior to use/storage.

Sludge organic carbon content and pH details are presented in Table 3 below.

Details on test conditions:
TEST CONDITIONS
- Buffer: none
- pH: 6.5 - 6.6 (silt loam soil, non-sterilised) and 6.7 - 6.8 (sterilised); 5.9 - 6.0 (loamy sand soil, non-sterilised and sterilised); 5.6 (clay loam soil, non-sterilised) and 5.4 - 5.5 (sterilised); 6.3 - 6.4 (activated sludge solids, non-sterilised and sterilised); 5.5 (sandy soil, sterilised)
- Suspended solids concentration: not reported

TEST SYSTEM
- Type, size and further details on reaction vessel: Pyrex® glass tubes supplied with Qorpak caps with aluminum liner. Size not reported
- Water filtered (i.e. yes/no; type of size of filter used, if any): NANOpure® deionized water.
- Soil/sediment/sludge-water ratio (if simulation test): solid: solution ratio of approximately 1: 10 for the soils and 1: 100 for the activated sludge solids
- Number of reaction vessels/concentration: 2 per sampling time point (9 per substrate for adsorption phase; 7 per substrate for desorption phase)
- Test performed in open system:
- Method of preparation of test solution: Dosing solutions of [14C] decanol were prepared by dilution of an aliquot of original [14C] decyl alcohol (WIL No. 11961) with ethanol: water = 1: 2. Radioactive concentration of the solutions was determined by liquid scintillation counting (LSC). Dosing solutions were maintained in a refrigerator and were administered by volumetric addition.
- Are the residues from the adsorption phase used for desorption: yes
Computational methods:
- Adsorption and desorption coefficients (Kd): All statistical calculations of the coefficients were performed by linear regressions using Microsoft Excel®
- Freundlich adsorption and desorption coefficients: as above
- Slope of Freundlich adsorption/desorption isotherms: as above
- Adsorption coefficient per organic carbon (Koc): as above
- Regression coefficient of Freundlich equation as above
Type:
Koc
Remarks:
Overall arithmetic mean
Value:
1 460
Temp.:
20 °C
Type:
Koc
Remarks:
(Silt loam soil)
Value:
1 010 - 1 042
Temp.:
20 °C
% Org. carbon:
4.2
Remarks on result:
other: The lower and higher range values are for the adsorption and desorption phases of the test, respectively.
Type:
Koc
Remarks:
(Loamy sand soil)
Value:
1 218 - 1 953
Temp.:
20 °C
% Org. carbon:
1.2
Remarks on result:
other: The lower and higher range values are for the adsorption and desorption phases of the test, respectively.
Type:
Koc
Remarks:
(Clay loam soil)
Value:
1 141 - 1 624
Temp.:
20 °C
% Org. carbon:
4.3
Remarks on result:
other: The lower and higher range values are for the adsorption and desorption phases of the test, respectively.
Type:
Koc
Remarks:
(Sandy soil)
Value:
1 160 - 1 877
Temp.:
20 °C
% Org. carbon:
0.51
Remarks on result:
other: The lower and higher range values are for the adsorption and desorption phases of the test, respectively.
Type:
Koc
Remarks:
(activated sludge solids)
Value:
1 433 - 1 766
Temp.:
20 °C
% Org. carbon:
28.57
Remarks on result:
other: The lower and higher range values are for the adsorption and desorption phases of the test, respectively.
Adsorption and desorption constants:
Table 4 below shows the coefficients relating to the adsorption and desorption phases of the study.

Recovery of test material:
The recovery of radioactivity in the Controls in non-sterilized systems after 24-hour equilibration was 82%-83% of AR. The recovery of radioactivity in the controls in Adsorption Kinetics test was 90.3% to 94.7% of AR (adsorption phase). Desorption equilibration in the Controls resulted in total recovery of 92% to 96% of applied radioactivity.
Concentration of test substance at end of adsorption equilibration period:
Silt loam soil: 0.38 - 20.6 µg/l (aq); 17.7 - 864 µg/kg (s)
Loamy sand soil: 0.72 - 44.3 µg/l (aq); 13.8 - 617 µg/kg (s)
Clay loam soil: 0.16 - 18.7 µg/l (aq); 9.02 - 886 µg/kg (s)
Sandy soil: 0.57 - 69.4 µg/l (aq); 4.00 - 382 µg/kg (s)
Activated sludge solids: 0.36 - 20.7 µg/l (aq); 167 - 8395 µg/kg (s)
Concentration of test substance at end of desorption equilibration period:
Silt loam soil: 0.22 - 12.7 µg/l (aq); 15.4 - 743 µg/kg (s)
Loamy sand soil: 0.32 - 19.8 µg/l (aq); 10.8 - 441 µg/kg (s)
Clay loam soil: 0.08 - 11.4 µg/l (aq); 8.33 - 782 µg/kg (s)
Sandy soil: 0.19 - 22.5 µg/l (aq); 2.45 - 198 µg/kg (s)
Activated sludge solids: 0.25 - 14.0 µg/l (aq); 140 - 7083 µg/kg (s)
Transformation products:
not measured
Details on results (Batch equilibrium method):
PRELIMINARY TEST
- Sample purity: Radiochemical purity >99%
- Weighed soil: n/a - the preliminary test was conducted to assess adsorption of the test substance on the surfaces of test vessels and on filters, and stability in 0.01 M CaCl2.
- Volume of CaCl2 solution: not reported
- Initial test substance concentration: not reported
- Test substance concentration in final solution: not reported
- Analytical test substance concentration in final solution: Recovery 98% to 104% of applied radioactivity (AR) in selected tube type and 78% to 82% of radioactivity from the selected separation technique (microcentrifugation).
- Other:

MAIN TEST: PERFORMANCE
- Test material stability during adsorption/desorption phase: Not acceptable; samples were gamma-sterilised / autoclaved to minimise biodegradation. 88-91% of applied radioactivity recovered. Minor amounts of radioactivity found in the aqueous phase after desorption equilibration are related to [14C] compound in the solutions remaining on the walls of the tubes after pouring out aqueous phase after adsorption step of the test.
- Experimental conditions maintained throughout the study: Yes
- Buffer/test substance interactions affecting sorption: no
- Further chemical interactions: no
- Buffer-catalyzed degradation of test substance: no
- Anomalies or problems encountered (if yes): n/a
- Other observations: no

TRANSFORMATION PRODUCTS
- Range of maximum concentrations in % of the applied amount: not identified

RESIDUES
- Total unidentified radioactivity (range) of applied amount: 9-12% of applied radioactivity not recovered
- Extractable residues (% of applied amount at end of study period): not reported
- Non-extractable residues (% of applied amount at end of study period): not reported

VOLATILIZATION
- % of the applied radioactivity present as volatile organics at end of study: not reported

Table 4 Average adsorption and desorption distribution coefficients of decanol in the test systems, calculated by linear fit of the isotherms.

Sample

Adsorption

Desorption

 

*

*

 

L kg-1

L kg-1

 

 

 

 

 

 

 

 

 

Silt Loam soil (TB-PF)

42.4

±

0.46

1010

58.9

±

0.55

1402

Loamy Sand soil (Roger Myron)

14.6

±

0.30

1218

23.4

±

0.56

1953

Clay Loam soil (DU-Loam)

49.0

±

0.52

1141

69.8

±

0.42

1624

Sandy soil (Speyer 2.1)

5.9

±

0.18

1160

9.6

±

0.39

1877

Activated Sludge solids

409

±

2.59

1433

505

±

2.92

1766

 

 

 

 

 

 

 

 

 

All calculations were performed using Excel®in full precision mode; calculations using rounded numbers presented in the tables may result in slightly different values.

*average values ± Standard Error.

Table 5 Parameters of Freundlich Equation for decanol adsorption and desorption isotherm

Sample

Adsorption*

Desorption*

 

1/n

Log()

R

1/n

Log()

R

 

 

 

 

 

 

 

Silt Loam soil (TB-PF)

0.9784

1.6623

0.9997

0.9661

1.8060

0.9998

Loamy Sand soil (Roger Myron)

0.9295

1.2853

0.9993

0.9095

1.4862

0.9993

Clay Loam soil (DU-Loam)

0.9724

1.7295

0.9998

0.9262

1.9094

0.9992

Sandy soil (Speyer 2.1)

0.9573

0.8674

0.9968

0.9036

1.1169

0.9962

Activated Sludge solids

0.9857

2.6291

0.9996

0.9848

2.7169

0.9993

 

 

 

 

 

 

 

* calculated by fit of the Log-Log plots of the isotherms; calculations were performed using Excel®in full precision mode. R is correlation coefficient between logarithms of the concentrations of the material in the solids and in the aqueous phase.

Validity criteria fulfilled:
yes
Conclusions:
A Koc value of 1460 (log value 3.16) was determined based on four standard soils and activated sludge solids, in a reliable study of adsorption and desorption using the batch equilibrium method, in accordance with the standard guideline and GLP.
Executive summary:

A Koc value of 1460 (log value 3.16) was determined based on four standard soils and activated sludge solids, in a reliable study of adsorption and desorption using the batch equilibrium method, in accordance with the standard guideline and GLP.

Description of key information

Adsorption/desorption: Koc 1490 for decan-1-ol (OECD 106)

Key value for chemical safety assessment

Koc at 20 °C:
1 490

Additional information

A recent and reliable study of adsorption and desorption using the batch equilibrium method (in compliance with OECD 106 and GLP) has been conducted with decan-1-ol. Based on tests with four soil samples and one sludge sample, the Koc value on average was 1460. Regression of the Kd values from this test against percentage organic carbon shows a very well correlated linear relationship, passing through the origin, which confirms that decanol is interacting only with the organic carbon constituents of the substrates, and corroborates the conclusion of Koc of approximately 1500. The result is considered to be reliable and acceptable for use in environmental exposure modelling.

It is notable that significant technical difficulties were encountered during method development for this study in natural standard soils, in that it was not possible to detect sufficient substance and establish equilibrium in non-sterilised soil samples, due to the rapid rate of biodegradation of the test substance by the soil microbiota.

For comparison purposes, estimated Koc values derived in the HPLC adsorption test (OECD 121) and also by various QSAR methods are available. A Koc study using HPLC (OECD 121) methodology was conducted for a range of linear aliphatic alcohols in accordance with ISO 17025 (Shell Global Solutions, 2013). The Koc result for decan-1-ol from this study was 802. This is within a factor of 2 of the OECD 106 study result and is considered to demonstrate the good performance of the HPLC method for this substance type, without the complications of biodegradation in the soil test substrate.

Koc values of 6330, 190 and 2490 were obtained using the well-established QSAR calculation method for 'predominantly hydrophobic' substances; the method for 'Alcohol' substances and the method for 'non-hydrophobic' substances respectively, developed by Sabljić and Güsten (1995) for the European Commission, and recommended in EU Guidance. The range of predictions covers the measured and HPLC values. Further details are presented in the endpoint study record.

Additionally, a Koc value of 390 has been sourced from secondary literature for decan-1-ol (Schuurmann, 2006). The original reference, with original Koc measurement work, was not available for review and no further information is available. The method used is not known.

Discussion of trends in the Category of C6-24 linear and essentially-linear aliphatic alcohols:

Substantial evidence exists within the alcohols Category, in the form of sewage sludge adsorption measurements, literature values, High Performance Liquid Chromatography (HPLC) estimates conducted in accordance with OECD Guideline 121, and a recent OECD Guideline 106 test in soils and a wastewater treatment plant sludge. Predictive methods based on log Kow and MCI have also been explored for members of this Category. The available measured data supports the following conclusions:

- The HPLC predictions correlate very well with the available measured Koc data, requiring no additional correction.

- Adsorption results in the OECD Guideline 106 study indicate that the alcohol interacts only with the organic carbon in the soils. This confirms the expectation that setting a value of Koc is sufficient to understand adsorption to the relevant substrates (soil, sediment, sludges).

- There are no confounding factors anticipated for the alcohols in this Category (e.g. unusual interaction with the stationary phase). Based on the structure and simple physical chemistry of decan-1-ol, there is every reason to believe that the Koc value obtained from the OECD 121 guideline study is valid and fit-for-purpose.

- Different log Kow-based QSAR predictions of Koc vary widely depending on which equation is selected.

- HPLC measured Koc values across the series show a predictable increase in Koc value as the carbon number increases. Regression analysis shows that the linear relationship between carbon number and log Koc value measured using this method is extremely well correlated with very low error.

Reference:

Sabljić A and Güsten H (1995) QSARs for soil sorption. in: overview of structure-activity relationships for environmental endpoints. Hermens JLM (ed), report prepared wtihin the framework of the project "QSAR for prediction of fate and effects of chemicals in the environment", an international project of the Environmental Technologies RTD programme (DG XII/D-1) of the European Commission under contract number EV5V-CT92-0211.