imidacloprid (ISO); 1-(6-chloropyridin-3-ylmethyl)-N-nitroimidazolidin-2-ylidenamine

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

12 Dec 1991 - 02 Apr 1992

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)

Version / remarks:

1981

Deviations:

yes

Remarks:

Only 2 different soils were tested, instead of 5

Qualifier:

according to guideline

Guideline:

other: EPA: Pesticide Assessment Guidelines, Subdivision N, Chemistry: Environmental Fate § 163-1, Leaching and Adsorption/Desorption Studies, 18. Oct. 1982

Version / remarks:

1982

Qualifier:

according to guideline

Guideline:

other: EPA: Pesticide Assessment Guidelines, Subdivision N, Chemistry: Environmental Fate § 163-1, Leaching and Adsorption/Desorption Studies, Addendum 6 on Data Reporting, by S.M. Creeger and E.B. Conerly, Jan. 1988

Version / remarks:

1988

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

20 °C

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0.304, 0.228, 0.150, and 0.031 mg imidacloprid/L
- Sampling interval: At 48 h duplicate test vessels of each concentration for each soil were analyzed.
- Sample preparation before analysis: After termination of the equilibration process the samples were centrifuged (~10,000 g), the clear supernatant of each sample was decanted off, aliquots of the supernatant were taken for 14C-measurement in the LSC and subsequently the pH was determined.

Matrix no.:

#1

Matrix type:

sandy loam

% Clay:

5

% Silt:

22.6

% Sand:

72.4

% Org. carbon:

1.4

pH:

7

CEC:

8 meq/100 g soil d.w.

Bulk density (g/cm³):

2.58

Matrix no.:

#2

Matrix type:

sandy loam

% Clay:

6.9

% Silt:

21.5

% Sand:

71.6

% Org. carbon:

6.3

pH:

6.3

CEC:

5 meq/100 g soil d.w.

Bulk density (g/cm³):

2.55

Details on matrix:

COLLECTION AND STORAGE
- Geographic location: Laacherhof AXXa: Laacherhof, Northrhine Westfalia,Germany; Borstel: Homann Farm, Lower Saxony, Germany
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): Prior to the beginning of the test the soils were air-dried and sieved through a 2 mm sieve. The residual moisture was determined by drying at 105 °C and was taken into consideration correspondingly when weighing the soils.

PROPERTIES
- Soil texture: sandy loam (Laacherhof AXXa); sandy loam (Borstel)
- % sand: Laacherhof AXXa: 72.4%; Borstel: 71.6%
- % silt: Laacherhof AXXa: 22.6%; Borstel: 21.5%
- % clay: Laacherhof AXXa: 5.0%; Borstel: 6.9%
- Soil taxonomic classification: Borstel: sandy, mixed, mesic
- Soil classification system: Borstel: Typic Dysplaggept
- pH: Laacherhof AXXa: 7.0 in H2O, 6.4 in CaCl2; Borstel: 6.3 in H2O, 5.6 in CaCl2
- Organic carbon (%): Laacherhof AXXa: 1.4%; Borstel: 1.3%
- CEC (meq/100 g): Laacherhof AXXa: 8; Borstel: 5
- Residual soil moisture (%): Laacherhof AXXa: 11.18%; Borstel: 7.25%
- Bulk density (g/cm3): Laacherhof AXXa: 2.58; Borstel: 2.55

Details on test conditions:

TEST CONDITIONS
- Buffer: The test substance was set up in 0.01 M CaCl2 solution with four concentrations (0.304, 0.228, 0.150, and 0.031 mg imidacloprid/L).
- pH: see section “Any other information on material and methods incl. tables”
- Suspended solids concentration:
- other: Temperature: 20 °C; Light conditions: Dark; Equilibration time: 48 h

TEST SYSTEM
- Type, size and further details on reaction vessel: Test vessel: Teflon centrifuge tubes with screw cap; volume: 43 mL; Parallel batches: 2; Mechanical shaker: Overhead shaker (25 ± 2 rpm)
- Water filtered (i.e. yes/no; type of size of filter used, if any): no
- Amount of soil/sediment/sludge and water per treatment (if simulation test): Samples of 5 g of each soil (related to dry weight) were weighed into centrifuge tubes in duplicate, 20 mL application solution of the different concentrations were added and they were shaken for 48 h.
- Soil/sediment/sludge-water ratio (if simulation test): Based on other adsorption/desorption studies of imidacloprid at higher concentration rates the soil/water ratio was adjusted to 1:4.
- Number of reaction vessels/concentration: The experiment was performed in 4 different concentrations (0.304, 0.228, 0.150, and 0.031 mg imidacloprid/L) in 2 parallel batches.
- Measuring equipment: LSC, TLC
- Test performed in open system: No; The test was performed in closed vessels.
- Method of preparation of test solution: The adsorption/desorption measurements were carried out with four concentrations of the test substance: 0.304 (A), 0.228 (B), 0.150 (C), and 0.031 mg/L (D). 14C-labeled imidacloprid was used for preparation of the application solutions without dilution with non-labeled test substance. Stock solution I: For preparation of the 0.01 M CaCI2 solution an amount of 4.38 g CaCI2 x 6H2O was weighed into a 2 L volumetric flask and filled up with distilled water to the calibration mark; Stock solution II (radioactive compound): The radioactively labeled test substance was completely dissolved in 1 mL methanol. An aliquote of 50uL was diluted with 1mL acetonitril. The radioactivity concentration of this solution as well as the radiochemical purity was determined by means of liquid scintillation counting (LSC) and TLC. Application solution A: The application solution A (0.304 mg/L) was prepared in a 1000 ml volumetric flask by adding 0.647 uL of stock solution II. The organic solvent was evaporated with a stream of nitrogen. Subsequently the flask was filled to 2/3 of its volume with 0.01 M CaCl2 solution, agitated for ca. 1 hour, ultrasonicated for 10 min and then filled up to the calibration mark. Subsequently aliquots were removed for radioactivity determination (3 x 0.1 mL); Application solution B. C. and D (0.228, 0.150, and 0.031 mg test substance/L): 75 mL (application solution B), 50 mL (application solution C) and 10 mL (application solution D) of the application solution A were pipetted into 100 mL volumetric flasks by means of bulb pipettes, filled up to the calibration mark with 0.01 M CaCl2 solution and shaken. Subsequently, aliquots were removed from the solutions for radioactivity determination (3x1 mL).
- Are the residues from the adsorption phase used for desorption: Yes; A volume of 20 mL of 0.01 M CaCI2 solution was added to the each test vessel. The vessels were again shaken for 48 h, centrifuged and aliquots were removed for radioactivity measurement. The radioactivity in the desorbed soil was determined by combustion of the soil for the determination of an overall radioactivity balance.
- Other:

Sample no.:

#1

Duration:

48 h

Conc. of adsorbed test mat.:

2.09 other: µg/5g

Temp.:

20 °C

Remarks:

Laacherhof soil

Sample no.:

#2

Duration:

48 h

Conc. of adsorbed test mat.:

2.64 other: µg/5g

Temp.:

20 °C

Remarks:

Borstel soil

Sample no.:

#3

Duration:

48 h

Conc. of adsorbed test mat.:

1.68 other: µg/5g

Temp.:

20 °C

Remarks:

Laacherhof soil

Sample no.:

#4

Duration:

48 h

Conc. of adsorbed test mat.:

2.09 other: µg/5g

Temp.:

20 °C

Remarks:

Borstel soil

Sample no.:

#5

Duration:

48 h

Conc. of adsorbed test mat.:

1.2 other: µg/5g

Temp.:

20 °C

Remarks:

Laacherhof soil

Sample no.:

#6

Duration:

48 h

Conc. of adsorbed test mat.:

1.45 other: µg/5g

Temp.:

20 °C

Remarks:

Borstel soil

Sample no.:

#7

Duration:

48 h

Conc. of adsorbed test mat.:

0.29 other: µg/5g

Temp.:

20 °C

Remarks:

Laacherhof soil

Sample no.:

#8

Duration:

48 h

Conc. of adsorbed test mat.:

0.35 other: µg/5g

Temp.:

20 °C

Remarks:

Borstel soil

Type:

Kd

Value:

1.52 L/kg

Temp.:

20 °C

Matrix:

#1

% Org. carbon:

1.4

Remarks on result:

other: Soil: Laacherhof

Type:

Koc

Value:

109 L/kg

Temp.:

20 °C

Matrix:

#1

% Org. carbon:

1.4

Remarks on result:

other: Soil: Laacherhof

Type:

Kd

Value:

2.14 L/kg

Temp.:

20 °C

Matrix:

#2

% Org. carbon:

1.3

Remarks on result:

other: Soil: Borstel

Type:

Koc

Value:

165 L/kg

Temp.:

20 °C

Matrix:

#2

% Org. carbon:

1.3

Remarks on result:

other: Soil: Borstel

Sample no.:

#1

Duration:

48 h

% Adsorption:

34.51

Remarks on result:

other: Laacherhof soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#2

Duration:

48 h

% Adsorption:

43.45

Remarks on result:

other: Borstel soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#3

Duration:

48 h

% Adsorption:

36.81

Remarks on result:

other: Laacherhof soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#4

Duration:

48 h

% Adsorption:

45.98

Remarks on result:

other: Borstel soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#5

Duration:

48 h

% Adsorption:

39.77

Remarks on result:

other: Laacherhof soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#6

Duration:

48 h

% Adsorption:

48.12

Remarks on result:

other: Borstel soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#7

Duration:

48 h

% Adsorption:

48.05

Remarks on result:

other: Laacherhof soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#8

Duration:

48 h

% Adsorption:

57.49

Remarks on result:

other: Borstel soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#1

Duration:

48 h

% Desorption:

39.78

Remarks on result:

other: Laacherhof soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#2

Duration:

48 h

% Desorption:

34.54

Remarks on result:

other: Borstel soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#3

Duration:

48 h

% Desorption:

39.55

Remarks on result:

other: Laacherhof soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#4

Duration:

48 h

% Desorption:

35.65

Remarks on result:

other: Borstel soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#5

Duration:

48 h

% Desorption:

34.2

Remarks on result:

other: Laacherhof soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#6

Duration:

48 h

% Desorption:

30.91

Remarks on result:

other: Borstel soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#7

Duration:

48 h

% Desorption:

35.68

Remarks on result:

other: Laacherhof soil

Remarks:

result given as mean value of 2 replicates

Sample no.:

#8

Duration:

48 h

% Desorption:

27

Remarks on result:

other: Borstel soil

Remarks:

result given as mean value of 2 replicates

Transformation products:

no

Details on results (Batch equilibrium method):

PRELIMINARY TEST
- Weighed soil: Samples of 5 g of each soil (related to dry weight) were weighed into centrifuge tubes in duplicates.
- Volume of CaCl2 solution: 20 mL application solution (test substance in 0.01 M CaCl2) of the different concentrations were added to 5g soil and they were shaken for 48 h.
- Initial test substance concentration: The test substance was set up in 0.01 M CaCl2 solution with four concentrations (0.304, 0.228, 0.150, and 0.031 mg imidacloprid/L).

MAIN TEST: PERFORMANCE
- Test material stability during adsorption/desorption phase: The test material was stable during the adsorption/desorption phase.
- Experimental conditions maintained throughout the study: Yes

Table 1: Distribution of radioactivity (Balance in % of the applied radioactivity)*

 

	adsorption solution [%]	desorption solution [%]	soil combustion [%]	Recovery [%]
A	58.78 ± 1.25	20.38 ± 0.20	19.30 ± 0.75	98.46 ± 0.31
B	57.02 ± 0.26	20.58 ± 0.56	19.78 ± 0.59	97.37 ± 0.29
C	53.46 ± 0.41	20.11 ±0.04	23.58 ± 0.32	97.16 ±0.69
D	46.49 ± 0.90	22.53 ±0.16	30.35 ± 0.23	99.37 ± 0.83

* Mean and difference of the individual values calculated from two test batches; Laacherhof 0.304 (A), 0.228 (B), 0.150 (C), and 0.031 mg/L (D).

 

 

Table 2: Distribution of radioactivity (Balance in % of the applied radioactivity)*

	adsorption solution [%]	desorption solution [%]	soil combustion [%]	Recovery [%]
A	51.66 ±0.12	20.14 ±0.27	26.48 ± 0.26	98.27 ± 0.42
B	50.68 ± 0.05	19.53 ±0.15	27.89 ± 0.03	98.10 ±0.17
C	47.14 ± 0.20	19.56 ±0.12	30.11 ±0.14	96.81 ±0.17
D	39.05 ± 0.77	19.12 ±0.38	38.36 ± 0.23	96.52 ± 0.92

* Mean and difference of the individual values calculated from two test batches; Borstel 0.304 (A), 0.228 (B), 0.150 (C), and 0.031 mg/L (D).

Table 3: Adsorption Constants of FREUNDLICH isotherms

 

Soil	Kd mL/g	1/n	r*	Koc mL/g
Laacherhof	1.52	0.7830	0.9996	109
Borstel	2.14	0.7857	0.9999	165

* coefficient of correlation

 

 

Table 4: Desorption Constants of FREUNDLICH isotherms

 

Soil	Kd mL/g	1/n	r*	Koc mL/g
Laacherhof	3.82	0.8771	0.9955	273
Borstel	4.21	0.8384	0.9987	324

* coefficient of correlation

Validity criteria fulfilled:

not applicable

Reference 2

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: EPA, Pesticide Assessment Guidelines, Subdivision N, Chemistry: Environmental Fate § 163-1, Leaching and Adsorption/Desorption Studies; October 18, 1982

Qualifier:

according to guideline

Guideline:

other: EPA, Pesticide Assessment Guidelines, Subdivision N, Chemistry: Environmental Fate § 163-1, Addendum on Data Reporting, Prep, by S. M. Creeger; September 30, 1986

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

20 ± 1 °C

Matrix type:

other: Borstel soil

% Clay:

7.2

% Silt:

24.5

% Sand:

68.3

% Org. carbon:

1.2

pH:

5.7

Matrix type:

other: Laacher Hof

% Clay:

5

% Silt:

22.6

% Sand:

72.4

% Org. carbon:

1.35

pH:

>= 6.4 - <= 6.9

Type:

Koc

Value:

153 L/kg

pH:

6.3

Temp.:

20 °C

Matrix:

Borstel soil

% Org. carbon:

1.2

Type:

Koc

Value:

235 L/kg

pH:

6.8

Temp.:

20 °C

Matrix:

Laacher Hof Soil

% Org. carbon:

1.35

Validity criteria fulfilled:

not applicable

Conclusions:

The adsorption of the test substance was investigated on two soils originated from "Borstel" and "Laacher Hof". When applying the active ingredient at concentrations corresponding to the 0.5 fold, 0.375 fold, 0.25 fold and 0.05 fold concentration of the maximum water solubility, the percentage of parent compound adsorbed to the soil phase varied between 18% and 28%.
The adsorption constant KD calculated by means of the Freundlich adsorption isotherm resulted in a value of 1.83 for soil "Borstel" and a value of 3.17 for soil "Laacher Hof". The soil carbon-based sorption KOC were calculated to 153 and 235.
Desorption tests showed that from the soil between 47% and 69% of the parent compound were desorbed again.

Reference 3

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

13 May - 16 Jun 1992

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: EPA, Pesticide Assessment Guidelines, Subdivision N, Chemistry: Environmental Fate § 163-1, Leaching and Adsorption/Desorption Studies; October 18, 1982

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

25 ± 1 °C

Matrix type:

other: Soil identification: Sand #296

% Clay:

1

% Silt:

0.3

% Sand:

98.7

% Org. carbon:

0.4

pH:

5.1

CEC:

3.9 meq/100 g soil d.w.

Bulk density (g/cm³):

1.41

Matrix type:

other: Soil identification:Loamy Sand #398

% Clay:

5.5

% Silt:

15.2

% Sand:

79.3

% Org. carbon:

0.6

pH:

4.5

CEC:

6 meq/100 g soil d.w.

Bulk density (g/cm³):

1.47

Matrix type:

other: Soil identification: Silt Loam #307

% Clay:

19.5

% Silt:

51.2

% Sand:

29.3

% Org. carbon:

2.6

pH:

5.8

CEC:

16.1 meq/100 g soil d.w.

Bulk density (g/cm³):

1.13

Matrix type:

other: Soil identification: Loam #318

% Clay:

23.5

% Silt:

47.2

% Sand:

29.3

% Org. carbon:

2

pH:

6.5

CEC:

10.8 meq/100 g soil d.w.

Bulk density (g/cm³):

1.05

Type:

Koc

Value:

411 L/kg

pH:

6.6

Temp.:

25 °C

Matrix:

Soil identification: Sand #396

% Org. carbon:

0.233

Type:

Koc

Value:

292 L/kg

pH:

6.9

Temp.:

25 °C

Matrix:

Soil identification: Loamy sand #398

% Org. carbon:

0.349

Type:

Koc

Value:

277 L/kg

pH:

7

Temp.:

25 °C

Matrix:

Soil identification: Silt loam #307

% Org. carbon:

1.51

Type:

Koc

Value:

315 L/kg

pH:

6.9

Temp.:

25 °C

Matrix:

Soil identification: Silt loam #307 (with sodium azide)

% Org. carbon:

1.51

Type:

Koc

Value:

296 L/kg

pH:

7.3

Temp.:

25 °C

Matrix:

Soil identification: Loam #318

% Org. carbon:

1.16

Validity criteria fulfilled:

not applicable

Conclusions:

Aqueous solutions of radiolabelled test substance were equilibrated with four soil types (sand, loamy sand, silt loam, loam) and the adsorption and desorption coefficients and constants were determined. Liquid scintillation counting analysis was employed to measure the test material concentrations in the aqueous phases. Following desorption, combustion-radioanalysis was used to demonstrate 14C-mass balance. The nominal concentrations of the 14C-labelled test substance for all soil types were 250, 187.5, 125, and 25 ppm.
The results of this study for the test substance on the four soil types studied yield a mean adsorption Koc value of 319, a medium mobility class for the test substance.

Reference 4

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

18 Jun - 11 Nov 1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: EPA, Pesticide Assessment Guidelines, Subdivision N, Chemistry: Environmental Fate § 163-1, Leaching and Adsorption/Desorption Studies; October 18, 1982

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

20 ± 1 °C

Matrix type:

other: Soil identification: Greenhouse soil (Kansas)

% Clay:

6

% Silt:

27

% Sand:

67

% Org. carbon:

1.4

pH:

5.2

CEC:

22 meq/100 g soil d.w.

Bulk density (g/cm³):

2.6

Matrix type:

other: Soil identification: Experimental farm Höfchen (Burscheid FRG)

% Clay:

9

% Silt:

89

% Sand:

2

% Org. carbon:

1.8

pH:

5.3

CEC:

10.5 meq/100 g soil d.w.

Bulk density (g/cm³):

1.7

Matrix type:

other: Soil identification: Standard soil (Jockgrim, Südpfalz, FRG)

% Clay:

3.5

% Silt:

8.7

% Sand:

87.8

% Org. carbon:

0.75

pH:

5.6

CEC:

4 meq/100 g soil d.w.

Bulk density (g/cm³):

2.4

Matrix type:

other: Soil identification: Soil Ranschbach (Landau, FRG)

% Clay:

42.7

% Silt:

42.3

% Sand:

15

% Org. carbon:

0.64

pH:

7.4

CEC:

21.1 meq/100 g soil d.w.

Bulk density (g/cm³):

2.1

Type:

Koc

Value:

256 L/kg

pH:

6.7

Temp.:

20 °C

Matrix:

Greenhouse soil (sandy loam soil)

% Org. carbon:

1.4

Type:

Koc

Value:

132 L/kg

pH:

6.4

Temp.:

20 °C

Matrix:

Soil Höfchen (silt soil)

% Org. carbon:

1.8

Type:

Koc

Value:

157 L/kg

pH:

6.6

Temp.:

20 °C

Matrix:

Standard soil 2.1 (low-humus sandy soil)

% Org. carbon:

0.75

Type:

Koc

Value:

212 L/kg

pH:

7.7

Temp.:

20 °C

Matrix:

Soil Ranschbach (silty clay soil)

% Org. carbon:

0.64

Validity criteria fulfilled:

not applicable

Conclusions:

The adsorption constants for NTN 33893 were determined in soil/water suspensions with sandy loam soil, silt soil, low-humus sandy soil as well as silty clay soil using parent compound concentrations of 290 mg/L - 29 mg/L. Depending upon the soil type the K values varied between 1.17 and 3.59.

The correlation between adsorption constants and leaching behaviour is known from the literature 5 /6. Thus, Guth 6) could show that substances having an adsorption constant ≥ 20 are retained in the upper 2 cm soil layer after rainfall at an amount of 200 mm. In contrast to that only those plant protectants having an adsorption constant of < 1, are washed into the soil deeper than 30 cm.

NTN 33893 is partly reversibly adsorbed to the soil colloids so that the parent compound remains available and is thus accessible to further degradation without the risk of leaching. The results of this study agree with those of leaching tests with packed columns 7 /8. The parent compound is to be classified as immobile.

Description of key information

log Koc = 2.14

Key value for chemical safety assessment

Koc at 20 °C:

137

Additional information

The mobility of (2E)-1-[(6-chloropyridin-3-yl)methyl]-N-nitroimidazolidin-2-imine in soil can be estimated based on its sorption constant. Four GLP studies are available for the substance.

 

The first study employed a batch equilibrium method according to OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method). Freundlich adsorption constants normalised to the organic carbon (OC) content Koc were determined for the substance in two different soils at 20 °C with values ranging from 109 to 165 (mean values: Koc 137, log Koc 2.14).

 

This result is supported by three more studies applying batch equilibrium methods according to EPA, Pesticide Assessment Guidelines, Subdivision N, Chemistry: Environmental Fate § 163-1, Leaching and Adsorption/Desorption Studies; October 18, 1982. Freundlich adsorption constants Koc were determined with values ranging from 132 to 411 (mean values: Koc 249, log Koc 2.40).