Dimethyl(octyl)amine

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption, other

Type of information:

experimental study

Adequacy of study:

key study

Study period:

4th May 2017 to 7th July 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Source - Albemarle (Magnolia), batch no. 4500083770
- Expiration date of the lot/batch: 20/1/18
- Purity test date: 21/1/15

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: ambient ( - Stability under test conditions: Stable, based on parental mass balance.
- Solubility and stability of the test substance in the solvent/vehicle:Stable under the test conditions (in 0.01 M CaCl2 solution) for at least 24 hours. Concentrations used accounted for the water solubility. No adsorption of the test item to the surface of the test vessel was observed after 24 hours of incubation
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium: No reactivity observed.

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: Stock solution (5500 mg/L of N,N-dimethyloctyamine, purity of 95% considered) was prepared in acetonitrile then stored deep frozen for the time scale of the test.
- Preliminary purification step (if any): None
- Final dilution of a dissolved solid, stock liquid or gel: Stock solution was diluted with acetonitrile to a concentration of 500 mg/L for use in tier 1 and 2 and tier 3 desorption kinetics. For the tier 3 adsorption/desorption experiments, five different application solutions were prepared from the 5500 mg/L stock solution by appropriate dilution with acetonitrile. The concentrations of the resulting application solutions were 5000 mg/L, 2000 mg/L, 500 mg/L, 200 mg/L and 50 mg/L N,N-dimethyloctylamine

Radiolabelling:

no

Test temperature:

20-25° C

Analytical monitoring:

yes

Details on sampling:

- Sampling interval:
For tier 1, selection of optimal soil/solution ratios, sampling time was at 0 and 24 hours after application
For tier 2, adsorption kinetics at one concentration of test item, sampling times were 0 (control only), 2,4,6,24 and 48 hours after application
For tier 3, desorption kinetics at one concentration of test item, sampling times were 2,4,6,24 and 48 hours after adsorption equilibrium was reached.
For tier 3, adsorption/desorption sampling times as for tier 3 desorption kinetics, except that the
aqueous phase was analysed only once after 24 hours of adsorption or desorption, respectively
- Sample storage before analysis: not stored before analysis

Matrix no.:

#1

Matrix type:

loamy sand

% Clay:

3.5

% Silt:

10.5

% Sand:

86

% Org. carbon:

0.68

pH:

4.84

CEC:

4.3 meq/100 g soil d.w.

Matrix no.:

#2

Matrix type:

loam

% Clay:

24.9

% Silt:

40.6

% Sand:

34.5

% Org. carbon:

1.89

pH:

7.41

CEC:

32 meq/100 g soil d.w.

Matrix no.:

#3

Matrix type:

clay

% Clay:

42

% Silt:

34.3

% Sand:

23.7

% Org. carbon:

1.68

pH:

7.29

CEC:

26.5 meq/100 g soil d.w.

Matrix no.:

#4

Matrix type:

silt loam

% Clay:

13.7

% Silt:

80.9

% Sand:

5.5

% Org. carbon:

1.2

pH:

6.01

CEC:

9.5 meq/100 g soil d.w.

Matrix no.:

#5

Matrix type:

loam

% Clay:

18.3

% Silt:

41

% Sand:

40.7

% Org. carbon:

2.25

pH:

4.32

Details on matrix:

See table under 'any other information on materials and methods incl. tables'

Details on test conditions:

TEST CONDITIONS
- pH: test item in 0.01 M CaCl2 = 6.61
The pH values after contact with the sorbent were measured after 24 hours of agitation at the appropriate soil to solution ratio and were 5.25, 7.25, 7.18, 6.24 and 4.52 for soils 2.1, 2.4, 6S, 02-A and 05-G, respectively. For Tier 1, the pH of the aqueous phase was measured before and after contact with the soil (after 24 hours of incubation) since it plays an important role in the whole adsorption process, especially for ionisable substances.
-Temperature: all experiments were done at a temperature always between 20 °C and 25 °C.


TEST SYSTEM
- Type, size and further details on reaction vessel: The test was performed by serial method in 100 mL glass flasks with PTFE screw caps.
- Water filtered: No
- Amount of soil and water per treatment (if simulation test): 10, 5,2 and 1 g of soil was used with 50 cm3 aqueous solution of test sustance to produce ratios of 1/5, 1/10, 1/25 and 1/50 respectively. 1 g soil with 100 cm3 aqueous solution was used to produce 1/100 ratio.
- Soil-water ratio (if simulation test):
The Tier 1 test was performed at three soil/solution ratios per soil in order to determine the optimum values for tier 2 and 3 tests. For Lufa 2.1, the ratios were 1/5, 1/10 and 1/25. For the other 4 soils, Lufa 2.4, Lufa 6S, RefeSol 02-A and RefeSol 05-G, the ratios were 1/25, 1/50 and 1/100.
The Tier 2 test was peformed at ratios based on Tier 1. The ratios were Lufa 2.1: 1/5; Lufa 2.4, 1/25; Lufa 6S, 1/100; RefeSol 02-A, 1/25 and RefeSol 05-G, 1/100.
Tier 3 tests were performed at same ratios as for Tier 2.
- Number of reaction vessels/concentration: 2
- Method of preparation of test solution:
A stock solution containing 5500 mg/L N,N-dimethyloctylamine (purity of 95 % considered) was prepared by weighing 0.1162 g of N,N-dimethyloctylamine into a 20 mL volumetric flask and adjusting the volume to 20.071 mL with acetonitrile. The stock solution was stored deep frozen in the dark for the time scale of the test.The stock solution was diluted with acetonitrile to a concentration of 500 mg/L. The diluted stock solution with the concentration of 500 mg/L N,N-dimethyloctylamine was used as application solution for Tier 1 and 2 and for Tier 3 Desorption Kinetics. For the Tier 3 experiment five different application solutions were prepared from the 5500 mg/L stock solution by appropriate dilution with acetonitrile. The concentrations of the resulting application solutions were 5000 mg/L, 2000 mg/L, 500 mg/L, 200 mg/L and 50 mg/L N,N-dimethyloctylamine.

Desorption kinetics - the five soils LUFA 2.1, 2.4 and 6S and RefeSol 02-A and 05-G were used for the desorption kinetic test at the soil/solution ratios that were determined in Tier 1. To each soil type, and appropriate soil/solution ratio, an aliquot of 50 µL test item solution (corresponding to 25 µg test item) were applied to the 1/5 and 1/25 samples and 100 µL of the test item solution (corresponding to 50 µg test item) were applied to the 1/100. After 24 h the suspensions were centrifuged at 2300 rpm (1266 g) for 4 minutes. The centrifugation speed was sufficient to remove particulate matter from the aqueous solution. The aqueous phase was recovered as completely as possible and an aliquot was diluted and measured by HPLC-MS/MS. Then, the desorption test followed using the samples from adsorption by adding fresh 0.01 M CaCl2 to adjust to 50 or 100 cm3, respectively. The sampling times were 2, 4, 6, 24 and 48 hours after adsorption equilibrium was reached.

Sample No.:

#1

Duration:

24 h

Initial conc. measured:

0.515 other: mg/L N,N-dimethyloctylamine in 0.01 M CaCl2 solution

pH:

5.25

Temp.:

>= 20 - <= 25 °C

Remarks:

pH is after 24 hours of equilibration. Soil type = LUFA 2.1.

Sample No.:

#2

Duration:

24 h

Initial conc. measured:

0.515 other: mg/L N,N-dimethyloctylamine in 0.01 M CaCl2 solution

pH:

7.35

Temp.:

>= 20 - <= 25 °C

Remarks:

pH is after 24 hours. Soil type = LUFA 2.4.

Sample No.:

#3

Duration:

24 h

Initial conc. measured:

0.515 other: mg/L N,N-dimethyloctylamine in 0.01 M CaCl2 solution

pH:

7.18

Temp.:

>= 20 - <= 25 °C

Remarks:

pH is after 24 hours. Soil type = LUFA 6S.

Sample No.:

#4

Duration:

24 h

Initial conc. measured:

0.515 other: mg/L N,N-dimethyloctylamine in 0.01 M CaCl2 solution

pH:

6.24

Temp.:

>= 20 - <= 25 °C

Remarks:

pH is after 24 hours. Soil type = RefeSol 02-A.

Sample no.:

#1

Duration:

24 h

Conc. of adsorbed test mat.:

1.43 mg/kg soil d.w.

pH:

5.25

Temp.:

20 °C

Remarks:

Concentration of adsorbed test material was calculated from the data in table 17 of study report after 24 hours, by using the values for mass adsorbed and mass of soil. Soil Type LUFA 2.1.

Sample no.:

#2

Duration:

24 h

Conc. of adsorbed test mat.:

6.6 mg/kg soil d.w.

pH:

7.35

Temp.:

20 °C

Remarks:

As for sample #1, except soil type = LUFA 2.4.

Sample no.:

#3

Duration:

24 h

Conc. of adsorbed test mat.:

26.54 mg/kg soil d.w.

pH:

7.18

Temp.:

20 °C

Remarks:

As for sample #1 and 2, except soil type = LUFA 6S

Sample no.:

#4

Duration:

24 h

Conc. of adsorbed test mat.:

9.14 mg/kg soil d.w.

pH:

6.24

Temp.:

20 °C

Remarks:

As for #1,2 and 3, except soil type = RefeSol 02-A

Sample no.:

#5

Duration:

24 h

Conc. of adsorbed test mat.:

39.6 mg/kg soil d.w.

pH:

4.52

Temp.:

20 °C

Remarks:

As for #1,2,3 and 4 except soil type RefeSol 05-G.

Key result

Sample No.:

#1

Type:

Koc

Value:

1 046 L/kg

pH:

5.25

Temp.:

20 °C

Matrix:

LUFA 2.1

% Org. carbon:

0.68

Key result

Sample No.:

#1

Type:

other: KFoc

Value:

651 other: [µg^1-1/n (cm 3 )^1/n g^-1]

pH:

5.25

Temp.:

20 °C

Matrix:

LUFA 2.1

% Org. carbon:

0.68

Key result

Sample No.:

#1

Type:

Kd

Value:

7.11 L/kg

pH:

5.25

Temp.:

20 °C

Matrix:

LUFA 2.1

% Org. carbon:

0.68

Key result

Sample No.:

#2

Type:

Koc

Value:

1 486 L/kg

pH:

7.35

Temp.:

20 °C

Matrix:

LUFA 2.4

% Org. carbon:

1.86

Key result

Sample No.:

#2

Type:

other: Kfoc

Value:

15.6 other: [µg^1-1/n (cm 3 )^1/n g^-1]

pH:

7.35

Temp.:

20 °C

Matrix:

LUFA 2.4

% Org. carbon:

1.89

Key result

Sample No.:

#2

Type:

Kd

Value:

28.1 L/kg

pH:

7.35

Temp.:

20 °C

Matrix:

LUFA 2.4

% Org. carbon:

1.89

Key result

Sample No.:

#3

Type:

Koc

Value:

5 966 L/kg

pH:

7.18

Temp.:

20 °C

Matrix:

LUFA 6S

% Org. carbon:

1.68

Key result

Sample No.:

#3

Type:

other: Kfoc

Value:

2 974 other: [µg^1-1/n (cm 3 )^1/n g^-1]

pH:

7.18

Temp.:

20 °C

Matrix:

LUFA 6S

% Org. carbon:

1.68

Key result

Sample No.:

#3

Type:

Kd

Value:

100 L/kg

pH:

7.18

Temp.:

20 °C

Matrix:

LUFA 6S

% Org. carbon:

1.68

Key result

Sample No.:

#4

Type:

Koc

Value:

7 297 L/kg

pH:

6.24

Temp.:

20 °C

Matrix:

RefSol 02-A

% Org. carbon:

1.2

Key result

Sample No.:

#4

Type:

other: Kfoc

Value:

2 644 other: [µg^1-1/n (cm 3 )^1/n g^-1]

pH:

6.24

Temp.:

20 °C

Matrix:

LUFA 6S

% Org. carbon:

1.2

Key result

Sample No.:

#4

Type:

Kd

Value:

87.6 L/kg

pH:

6.24

Temp.:

20 °C

Matrix:

LUFA 6S

% Org. carbon:

1.2

Key result

Sample No.:

#5

Type:

Koc

Value:

19 804 L/kg

pH:

4.52

Temp.:

20 °C

Matrix:

RefeSol 05-G

% Org. carbon:

2.25

Key result

Sample No.:

#5

Type:

other: Kfoc

Value:

5 648 other: [µg^1-1/n (cm 3 )^1/n g^-1]

pH:

4.52

Temp.:

20 °C

Matrix:

RefeSol 05-G

% Org. carbon:

2.25

Key result

Sample No.:

#5

Type:

Kd

Value:

446 L/kg

pH:

4.52

Temp.:

20 °C

Matrix:

RefeSol 05-G

% Org. carbon:

2.25

Adsorption and desorption constants:

Freundlich adsorption exponent (1/n):
LUFA 2.1, 1/n = 0.719
LUFA 2.4, 1/n = 0.653
LUFA 6S, 1/n = 0.604
*RefeSol 02-A, 1/n = 0.598
*RefeSol 05-G, 1/n = 0.566
*the replicates below LOQ were included for the calculation of the Freundlich adsorption coefficient, because of the low variance between the replicates and the high R^2 values for the linear plots

Freundlich desorption exponent (1/n):
LUFA 2.1, 1/n = 0.727
LUFA 2.4, 1/n = 0.717
LUFA 6S, 1/n = 0.652
*RefeSol 02-A, 1/n = 0.635
*RefeSol 05-G, 1/n = 0.579
*the replicates below LOQ were included for the calculation of the Freundlich adsorption coefficient, because of the low variance between the replicates and the high R^2 values for the linear plots

Recovery of test material:

In the two control samples (only 0.01 M CaCl2 solution containing the test item without soil) of the Tier 1 experiment, the mean recovery was 101.3 % after 24 hours of application. Therefore the test item was stable under test conditions for at least 24 hours. Furthermore, no adsorption of the test item to the surface of the test vessel was observed after 24 hours of incubation.

Concentration of test substance at end of adsorption equilibration period:

See table under section for 'any other information on results incl.tables'

Concentration of test substance at end of desorption equilibration period:

See table under section for 'any other information on results incl.tables'

Sample no.:

#1

Duration:

48 h

% Adsorption:

96.8

Remarks on result:

other: % Mass Balance

Remarks:

Result shown is % mass balance (taken from table 15 of study report), NOT % adsorption. The %adsorption header in the third column is misleading, given that the title of this section is 'mass balance(%) at end of adsorption phase'

Sample no.:

#2

Duration:

48 h

% Adsorption:

94.9

Remarks on result:

other: As above

Remarks:

As above

Sample no.:

#3

Duration:

48 h

% Adsorption:

97.5

Remarks on result:

other: As above

Remarks:

As above

Sample no.:

#4

Duration:

48 h

% Adsorption:

93.1

Remarks on result:

other: As above

Remarks:

As above

Sample no.:

#5

Duration:

48 h

% Adsorption:

92.5

Remarks on result:

other: As above

Remarks:

As above

Sample no.:

#1

Remarks on result:

not measured/tested

Sample no.:

#2

Remarks on result:

not measured/tested

Sample no.:

#3

Remarks on result:

not measured/tested

Sample no.:

#4

Remarks on result:

not measured/tested

Sample no.:

#5

Remarks on result:

not measured/tested

Transformation products:

no

Remarks:

High mass balance supports lack of any major transformation products.

Details on results (Batch equilibrium method):

Tier 3 - Desorption kinetics - The amount of desorption was < 75 % of the amount adsorbed within 24 hours.
Tier 3 - Results for the concentrations of the test material in soil and aqueous solution at adsorption and desorption equilibrium for different soil types and initial concentrations for the test material, are shown in tabular form under section 'any other information on results incl. tables'.

Statistics:

The arithmetic mean was calculated for averaging replicate analysis data and residue data from the duplicate test systems analysed per sampling interval.
No statistical outlier rejection procedures were used.

Concentration of AD 1 at adsorption equilibrium after 24 hours in the aqueous phase and bound

SOIL TYPE	Initial concentration (mg/L)	Mean concentration in aqueous solution (mg/L)	Mean concentration in soil [µg/g]
LUFA 2.1 (soil: solution ratio 1/5)	4.95	3.08	9.35
	2.00	1.03	4.86
	0.488	0.208	1.40
	0.201	0.0679	0.667
	0.0508	0.0130	0.189
LUFA 2.4 (soil: solution ratio 1/25)	4.95	3.46	37.3
	2.00	1.31	17.3
	0.488	0.243	6.11
	0.201	0.0802	3.03
	0.0508	0.0132	0.939
LUFA 6S (soil: solution ratio 1/100)	4.95	3.86	108
	2.00	1.39	61.4
	0.488	0.251	23.6
	0.201	0.0880	11.3
	0.0508	0.0140	3.68
RefeSol 02-A (soil: solution ratio 1/25)	4.95	2.71	56.0
	2.00	0.853	28.7
	0.488	0.118	9.24
	0.201	0.0329	4.21
	0.0508	0.00424*	1.16
RefeSol 05-G (soil: solution ratio 1/100)	4.95	2.89	206
	2.00	0.813	119
	0.488	0.101	38.7
	0.201	0.0260	17.5
	0.0508	0.00367*	4.71

 

*value below LOQ, but above LOD (calculated value from the analysis is used for evaluation), low variance between the replicates so data deemed acceptable for use in the calculation of the Freundlich

Concentration of AD 1 at desorption equilibrium after 24 hours in the aqueous phase and bound to soil:

SOIL TYPE	Initial concentration (mg/L)	Mean concentration in aqueous solution (mg/L)	Mean concentration in soil [µg/g]
LUFA 2.1 (soil: solution ratio 1/5)	2.12	0.903	6.00
	1.06	0.364	3.46
	0.293	0.0821	1.05
	0.140	0.0304	0.538
	0.0392	0.00604	0.163
LUFA 2.4 (soil: solution ratio 1/25)	1.62	0.740	22.0
	0.742	0.342	9.95
	0.254	0.0871	4.15
	0.123	0.0357	2.20
	0.0380	0.00762	0.759
LUFA 6S (soil: solution ratio 1/100)	1.13	0.584	54.1
	0.629	0.287	34.2
	0.239	0.0699	16.9
	0.114	0.0315	8.28
	0.0369	0.00704	2.99
RefeSol 02-A (soil: solution ratio 1/25)	2.32	0.797	38.0
	1.17	0.311	21.5
	0.374	0.0655	7.69
	0.170	0.0183	3.78
	0.0468	0.00306*	1.09
RefeSol 05-G (soil: solution ratio 1/100)	2.11	0.742	136
	1.20	0.344	85.4
	0.389	0.0560	33.3
	0.176	0.0167	15.9
	0.0473	0.00217*	4.50

*value below LOQ, but above LOD (calculated value from the analysis is used for evaluation), low variance between the replicates so data deemed acceptable for use in the calculation of the Freundlich

Validity criteria fulfilled:

yes

Conclusions:

The adsorption/desorption properties of N,N-dimethyloctylamine were determined in five soils covering a range of physico-chemical properties from Germany (2.1, 2.4, 6S, 02-A and 05-G), according to OECD guideline 106 (2000).

Tier 1 was initially performed at a concentration of 0.486 mg/L N,N-dimethyloctylamine in 0.01 M CaCl2 solution with the soils 2.1 (soil/solution ratio 1/5, 1/10 and 1/25) and 2.4, 6S, 02-A and 05-G (soil/solution ratios 1/25, 1/50 and 1/100) using the indirect method under sterile conditions with an equilibration time of 24 hours.

The adsorption 24 hours after application was 57.4 % for soil 2.1 at a soil/solution ratio of 1/5, 52.9 % for soil 2.4 at a soil/solution ratio of 1/25, 54.0 % for soil 6S at a soil/solution ratio of 1/100, 77.4 % for soil 02-A at a soil/solution ratio of 1/25 and 85.5 % for soil 05-G at a soil/solution ratio of 1/100.

The mean parental mass balance showed good recovery for the appropriate soil/solution ratios (average of recovery between 99.7 to 101.9 %). Due to the results of Tier1, Tier 2 was performed at a concentration of 0.515 mg/L N,N-dimethyloctylamine in 0.01 M CaCl2 solution with all soils at the appropriate soil/solution ratio using the serial method under sterile conditions.

The mass balance was between 92.5 % and 97.5 % for all soils, indicating thatthe test item was stable during the test period under sterile conditions. The Koc value after 24 hours of incubation ranged from 1046 cm3/g to 19804 cm3/g. The mobility class according to Briggs (1973) is classified as Immobile for all five soils.

Tier 3 Desorption Kinetics was performed at a concentration of 0.491 mg/L N,N-dimethyloctylamine in 0.01 M CaCl2 solution with all soils at the appropriate soil/solution ratio using the serial method under sterile conditions.As desorption in all soils was below 75 %, the adsorption of N,N-dimethyloctylamine is not considered to be reversible according to OECD 106.

The organic carbon normalized Freundlich adsorption coefficient ranged from 651 to 5648 µg^1-1/n (cm3)^1/n g^-1. The organic carbon normalized Freundlich desorption coefficient was between 991 and 7310 µg^1-1/n (cm3)^1/n g^-1.

Executive summary:

The adsorption/desorption properties of N,N-dimethyloctylamine were determined in five different soils of European origin (LUFA 2.1, 2.4 and 6S, RefeSol 02-A and 05-G), applying the batch equilibrium method according to OECD guideline 106 (2000). The soils exhibited a range of different properties important for sorption i.e. organic carbon content, cation exchange capacity, pH value and clay content.The method validation according to guideline SANCO/3029/99, rev. 4 was performed successfully within this study.

The Tier 1 test was performed at a concentration of 0.486 mg/L test item in 0.01 M CaCl2solution under sterile conditions at three soil/solution ratios per soil using the indirect method.

The mass balance was carried out after extraction of the soils at the appropriate soil/solution ratio of the Tier 1 experiment after 24 hours of incubation. For soils 2.1, 2.4, 6S, 02-A and 05-G 99.8 %, 99.7 %, 101.9 %, 101.0 % and 100.9 % were recovered, respectively. The recovery for the glass flasks containing CaCl2-solution without soil was 101.3 %. Based  on  the  results  of  Tier 1,  Tier 2  was  performed  at  a  concentration  of  0.515 mg/L N,N-dimethyloctylamine in 0.01 M CaCl2solution under sterile conditions at the appropriate soil/solution ratio using the indirect and serial method. Tier 2 Adsorption kinetics were measured after 2, 4, 6, 24 and 48 hours of incubation.

The mass balance was carried out after extraction of the soils at the appropriate soil/solution ratio of the Tier 2 experiment after 48 hours of incubation. For soils 2.1, 2.4, 6S, 02-A and 05-G 96.8 %, 94.9 %, 97.5 %, 93.1 % and 92.5 % were recovered, respectively. Desorption kinetics were determined 2, 4, 6, 24 and 48 hours after a 24 hours adsorption phase in Tier 3 experiments. The desorption of the test item from soils 2.1, 2.4, 6S, 02-A and 05-G ranged from 13.1 % to 31.8 % after 24 hours of agitation, thus indicating that adsorption is irreversible according to OECD 106.

The adsorption isotherms (Tier 3) were determined under sterile conditions at the appropriate soil/solution ratio and at five actual test item concentrations (4.95, 2.00, 0.488, 0.201 and 0.0508 mg/L) and an adsorption equilibration time of 24 hours.

The desorption isotherms (Tier 3) were estimated at the appropriate soil/solution ratio and at five test item concentrations resulting from the adsorption test concentrations and a desorption equilibration time of 24 hours.

Description of key information

The Koc values ranged from 1046 to 19804 depeding upon the soil type, these Koc values are high and all it can be concluded that AD-1 is immobile in soil. The mean value of all of the reported values will be used as the key value for the environmental risk assessment.

Key value for chemical safety assessment

Koc at 20 °C:

7 120