N-ethylpropylamine

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

01.2022 - 05.2022

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)

Qualifier:

according to guideline

Guideline:

other: SANTE/2020/12830, rev.1 (2021)

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Specific details on test material used for the study:

TEST ITEM
- Name of test substance: N-ethylpropylamine
- Test substance No.: 05/0042-4
- Batch identification: B987 - 20210115
- CAS No.: 20193-20-8
- Contents: 87.4 +/- 0.3g/100g; water: 10.8g/100g
- Homogeneity: Homogeneous
- Physical state/Appearance: Liquid/colorless, clear

Radiolabelling:

no

Test temperature:

All experiments were done at a temperature between 20°C and 25°C.

Details on study design: HPLC method:

HPLC system
- HPLC system: Agilent 1290 Series HPLC system (vacuum solvent degasser, binary HPLC pump), MayLab ComboSwitch column oven and CTC Analytics HTS-xt PAL Autosampler.
- Pre-column: Phenomenex C18 guard column (AJO-4287): Length 4 mm, i.d. 3 mm.
- Column: Phenomenex Luna PFP 3µ C18 (2) 100A, No. 466862-1, 150 mm × 3 mm, 3 µm
- Column oven temperature: 40°C
- Injection volume: 10 µL
- Retention time: N-Ethylpropylamine: approx. 1.2 min

Mass spectrometer system
- MS system: TripleQuad 6500+ System, SCIEX (Triple quadrupole mass spectrometer)
- Ionisation type: Electrospray ionisation (ESI, TurboIonSpray)
- Scan type: MS/MS, Multiple Reaction Monitoring (MRM)

MOBILE PHASES
- Type: Eluent A: Water containing 0.1% Formic Acid; Eluent B: Acetonitrile containing 0.1% Formic acid

Analytical monitoring:

yes

Details on sampling:

- Tier 1 Adsorption Preliminary study:
The sampling times were 0 (only control samples) and 24 hours after application.

- Tier 2 Adsorption Kinetics:
The sampling times were 0, 2, 6, 18, 24 and 48 hours after application.

- Tier 3 Desorption Kinetics and Adsorption and Desorption Isotherm:
The sampling times were 2, 4, 6, 24 and 48 hours after adsorption equilibrium was reached (single concentration).
The sampling times were 24 hours after application for the adsorption test and 18 hours after adsorption for the desorption test (five concentrations).

Matrix no.:

#1

Matrix type:

loamy sand

% Clay:

3.9

% Silt:

8.7

% Sand:

87.5

% Org. carbon:

0.61

pH:

4.7

CEC:

3.1 meq/100 g soil d.w.

Bulk density (g/cm³):

1.435

Matrix no.:

#2

Matrix type:

sandy loam

% Clay:

10.6

% Silt:

15

% Sand:

74.4

% Org. carbon:

1.77

pH:

5.6

CEC:

8.5 meq/100 g soil d.w.

Bulk density (g/cm³):

1.224

Matrix no.:

#3

Matrix type:

sandy loam

% Clay:

7.4

% Silt:

33.1

% Sand:

59.5

% Org. carbon:

0.66

pH:

6.2

CEC:

6 meq/100 g soil d.w.

Bulk density (g/cm³):

1.302

Matrix no.:

#4

Matrix type:

loam

% Clay:

24.5

% Silt:

42.9

% Sand:

32.6

% Org. carbon:

1.83

pH:

7.5

CEC:

17.6 meq/100 g soil d.w.

Bulk density (g/cm³):

1.206

Matrix no.:

#5

Matrix type:

silty clay

% Clay:

11.1

% Silt:

48.8

% Sand:

40

% Org. carbon:

2.66

pH:

7.4

CEC:

not specified

Details on matrix:

The study was carried out in five different soil types soil 2.1; 2.2, 2.3, 2.4 and 0-6A varying in their properties e.g. texture, pH, total organic carbon, or cation exchange capacity. The soils were sampled from the top 20 cm soil layer in December 2021 by LUFA Speyer and January 2022 by Fraunhofer Institute IME.

The soils were delivered already sieved to a particle size ≤ 2 mm. The soils were air-dried at the test facility at ambient temperature. The dry mass of the soil was determined in accordance to the facility’s SOP. For all calculations the mass of soil refers to dry mass, i.e., the weight of soil corrected for moisture content.

Details on test conditions:

APPLICATION PROCEDURE

- Tier 1 Adsorption Preliminary study:
An aliquot of 0.50 mL application solution (corresponding to 50 µg test item) was added to the soil/0.01 M-CaCl2 suspension (soil/solution ratio 1/1 and 1/2) and an aliquot of 1.25 mL application solution (corresponding to 125 µg test item) was added to the soil/0.01 M CaCl2 suspension (soil/solution ratio 1/5). With the addition of the application solution the final volume was achieved and the test vessel was sealed. The test system was then well mixed.
The nominal test concentration for the preliminary test (Tier 1) was 5.0 µg/mL and the actual test item concentration was determined in the control samples by LC-MS/MS analysis to be 5.19 µg/mL.

- Tier 2 Adsorption Kinetics:
An aliquot of 0.5 mL application solution (corresponding to 50 µg test item) was added to the soil/0.01 M CaCl2 suspension (soil/solution ratio 1/1). With the addition of the application solution the final volume was achieved and the test vessel was sealed. The test system was then well mixed.
The nominal test concentration for the preliminary test (Tier 2) was 5.0 µg/mL and the actual test item concentration was determined in the control samples by LC-MS/MS analysis to be 5.26 µg/mL.

- Tier 3 Desorption Kinetics and Adsorption and Desorption Isotherm:
The nominal test concentration for the Tier 3 Desorption kinetic experiment was 5.0 µg/mL and the actual test item concentration was determined in the control samples by LC-MS/MS analysis to be 5.29 µg/mL. The nominal test concentrations for the Tier 3 Adsorption/ Desorption experiment were 5.0, 1.0, 0.50, 0.10 and 0.050 µg/mL and the actual test item concentrations were determined in the control samples by LC-MS/MS analysis to be 5.7, 1.1, 0.55, 0.097 and 0.047 µg/mL, respectively, for the soil 2.2.
For the soils 2.4 and 06-A, the nominal test concentrations for the Tier 3 experiment were 25, 5.0, 2.5, 0.50 and 0.25 µg/mL and the actual test item concentrations were determined in the control samples by LC-MS/MS analysis to be 28, 5.6, 2.7, 0.50 and 0.26 µg/mL, respectively, for the soils 2.4 and 06-A.


TEST PROCEDURE

- Tier 1 Adsorption Preliminary study:
All five soils and three soil/solution ratios were used.
--> 10 g soil and 10 cm^3 aqueous solution of the test substance (ratio 1/1);
--> 5 g soil and 10 cm^3 aqueous solution of the test substance (ratio 1/2);
--> 5 g soil and 25 cm^3 aqueous solution of the test substance (ratio 1/5);
All experiments, including controls and blanks, were performed with the parallel method in duplicate. 0.50 mL of the test item solution (corresponding to 50 µg test item) were applied to the 1/1 and 1/2 samples and 1.25 mL (corresponding to 125 µg test item) of the test item solution were applied to the 1/5 samples for the non-sterile Tier 1 experiments (duplicates were used for each soil type). The sampling times were 0 (only control samples) and 24 hours after application.
Per various sample volume (10 and 25 cm^3) ,two adsorption control samples were prepared in 0.01 M CaCl2 solution by treatment with the test item and were subjected to the same steps as the test systems, in order to check the stability of the test item in 0.01 M CaCl2 solution and its possible adsorption on the surfaces of the test vessels. The pH of the aqueous phase was measured before and after contact with the soil (after 48 hours of incubation) since it plays an important role in the whole adsorption process, especially for ionisable substances.

- Tier 2 Adsorption Kinetics:
Based on the results of Tier 1 experiments, the Tier 2 test was performed at a soil/solution ratio of 1/1 (10 g soil and 10 cm^3 aqueous solution) for all soils (2.1, 2.2, 2.4, 12-060, 06-A) using the parallel method in duplicate. An aliquot of 0.50 mL test item solution were applied (corresponding to 50 µg test item) to each sample (duplicates were used for each soil type).
The sampling times were 0, 2, 6, 18, 24 and 48 hours after application.
Two dose and absorption control samples containing only 0.01 M CaCl2 solution were treated with the test item and were subjected to the same steps as the test systems, in order to check the stability of the test item in 0.01 M CaCl2 solution and its possible adsorption to the surface of the test vessel.
During the adsorption test, the pH of the aqueous phase was measured before and after contact with the soil since it plays an important role in the whole adsorption process, especially for ionisable substances.

- Tier 3 Desorption Kinetics and Adsorption and Desorption Isotherm at one Concentration of the test item:
The three soils 2.2, 2.4 and 06-A were used for the desorption kinetic test at the soil/solution ratio 1/1. All experiments, including controls, were performed with the serial method. 0.50 mL of application solution were applied (corresponding to 50µg test item) to each sample (duplicates were used for each soil type). After 18 h the suspensions were centrifuged at 4000 rpm for 5 minutes. 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 10 cm^3. The sampling times were 2, 4, 6, 24 and 48 hours after adsorption equilibrium was reached.

- Tier 3 Desorption Kinetics and Adsorption and Desorption Isotherm at five Concentrations of the test item:
Five test item concentrations (5.7, 1.1, 0.55, 0.097 and 0.047 µg/mL, equivalent to 57, 11, 5.5, 0.97 and 0.47 µg N-Ethylpropylamine for the soil 2.2 and 28, 5.6, 2.7, 0.50 and 0.26 µg/mL, equivalent to 276, 56, 27, 5.0 and 2.6 µg N-Ethylpropylamine for the soils 2.4and 06-A, respectively) were used, covering two orders of magnitude; in the choice of these concentrations the water solubility and the resulting aqueous equilibrium concentrations were taken into account. The soil/solution ratio 1/1 (10 g soil and 10 cm3 aqueous solution of the test substance) per soil was kept along the study.
The adsorption and desorption test was performed as followed.
Each experiment (one soil and five treatment levels) was done in duplicate to allow estimation of the variance of the results. For each soil, one blank control (no test item) were prepared and treated in the same manner as the spiked soil samples and an aliquot of the aqueous phase of each blank was measured by LC MS/MS. The test was performed by the parallel method in 50mL PE tubes with sealed screw caps. Agitation was performed on a horizontal shaker with a frequency of around 300 rpm to keep the soil dispersed in the aqueous volume.
After 24 h the suspensions were centrifuged at 4000 rpm for 5 minutes. The aqueous phase was recovered as completely as possible. Then, the desorption test followed using the samples from adsorption by adding 0.01 M CaCl2 to adjust 10 cm^3. The sampling times were 24 hours after application for the adsorption test and 18 hours after adsorption for the desorption test. The adsorption and desorption test were performed as described in chapter 4.4, except that the aqueous phase was analysed only once after 24 hours of adsorption or 18 hours of desorption, respectively. The equilibrium concentrations in the solution were determined.
The amount adsorbed was calculated from the depletion as a function of the equilibrium concentration of the test item. The desorbed mass per unit mass of soil was plotted as a function of the equilibrium concentration of the test item. The logarithm of the desorbed mass was plotted as a function of the logarithm of the equilibrium concentration of the test item.

Computational methods:

The Freundlich coefficient KF and 1/n were obtained by regression analysis of the plotted function using the logarithm of the concentration of the test item bound to soil versus the test item in the aqueous phase. The y axis intercept of the regression function is equivalent to the log KF value and the slope is equivalent to 1/n.

Key result

Sample No.:

#1

Type:

Koc

Value:

41.36 other: (µg^(1-1/n))*((cm^3)^1/n)*g^-1)

Matrix:

Soil 2.2, Soil 2.4 and Soil 06-A

Remarks on result:

other: Arithmetic mean of all 3 soils

Sample No.:

#2

Type:

Koc

Value:

26.4 other: (µg^(1-1/n))*((cm^3)^1/n)*g^-1)

pH:

6.3

Matrix:

Soil 2.2

% Org. carbon:

1.77

Sample No.:

#3

Type:

Koc

Value:

32.5 other: (µg^(1-1/n))*((cm^3)^1/n)*g^-1)

pH:

7.4

Matrix:

Soil 2.4

% Org. carbon:

1.83

Sample No.:

#4

Type:

Koc

Value:

65.2 other: (µg^(1-1/n))*((cm^3)^1/n)*g^-1)

pH:

7.4

Matrix:

Soil 06-A

% Org. carbon:

2.66

Details on results (HPLC method):

Based on the results of Tier 1 and 2, Tier 3 was performed with three soils at a soil/solution ratio of 1/1 and a sampling time of 24 hours after application.
For the soil 2.2, each samples contained an actual initial amount of 5.5, 1.1, 0.55, 0.097 and 0.047 µg/mL test item in 10 mL 0.01 M CaCl2, respectively.
For the soils 2.4 and 06-A, each samples contained an actual initial amount of 28, 5.6, 2.7, 0.50 and 0.26 µg/mL test item in 10 mL 0.01 M CaCl2, respectively.
In the two adsorption control samples (only 0.01 M CaCl2 solution containing the test item without soil) of the Tier 3 experiment the mean recovery was in the range of 87 % and 106 % after 42 hours of application. Therefore the test item was stable in solution without soil during the whole experimental period. Furthermore, no adsorption of the test item to the surface of the test vessel was observed 42 hours after incubation. The logarithm transformed data showed linear fits. Therefore, the Freundlich adsorption coefficient was calculated by linear regression.

Adsorption and desorption constants:

Desorption constant Koc [(µg^(1-1/n))*((cm^3)^1/n)*g^-1)]: 254 (Soil 2.2), 9,77 (Soil 2.4), 177 (Soil 06-A)

Recovery of test material:

Mean recovery [%]: 106 (Soil 2.2), 110 (Soil 2.4), 107 (Soil 06-A)

Transformation products:

not specified

 

Amount Adsorbed Soil after 24 hours for Soil to Solution Ratio 1/1, 1/2 and 1/5 (Tier 1)
	Parameters	Soil/Solution Ratio	Soil/Solution Ratio	Soil/Solution Ratio
		1/1	1/2	1/5
Soil 2.1	A %	15	5.4	3.5
Soil 2.2	A %	12	-3.9	-14
Soil 2.3	A %	9.4	-4.6	-2.8
Soil 2.4	A %	37	24	10
Soil 06-A	A %	60	42	22

 

Adsorption Coefficient after 24 and 48 hours for Soil to Solution Ratio 1/1 (Tier 2, Adsorption Kinetic)
	Parameters	Soil 2.1	Soil 2.2	Soil 2.3	Soil 2.4	Soil 06-A
Indirect Method
Mean 24 hours and	A [%]	11	25	20	39	61
48 hours	Kd [cm^3/g]	0.119	0.327	0.254	0.647	1.59
1/1	Koc [cm^3/g]	19.5	18.5	38.5	35.4	59.6
	% oc	0.61	1.77	0.66	1.83	2.66
Direct Method
Mean 24 hours and	A [%]	7.3	20	17	31	48
48 hours	Kd [cm^3/g]	0.0814	0.26	0.216	0.517	1.23
1/1	Koc [cm^3/g]	13.3	14.7	32.8	28.3	46.3
	% oc	0.61	1.77	0.66	1.83	2.66

 

Parental Mass Balance after 24 and 48 hours of Incubation (Tier 2 Adsorption Kinetic)
Sample	Equilibration Time	Ratio	Replicate	Recovery [%]	Mean Recovery [%]
Soil 2.1	24	1/1	1	96	97
			2	94
	48		1	98
			2	99
Soil 2.2	24	1/1	1	97	95
			2	94
	48		1	95
			2	93
Soil 2.3	24	1/1	1	97	97
			2	97
	48		1	96
			2	99
Soil 2.4	24	1/1	1	93	92
			2	93
	48		1	92
			2	90
Soil 06-A	24	1/1	1	90	86
			2	88
	48		1	84
			2	82

 

Time Dependent Course of Desorption (Soil 2.2, 2.4 and 06-A) for Soil to Solution Ratio 1/1 (Tier 3 Desorption Kinetics)
Soil 2.2	Desorption [%]
time [h]		4	18			24		48
1/1	Sample 1	55	39			41		34
	Sample 2	52	38			41		31
Soil 2.4	Desorption [%]
time [h]		2		4		24	48
1/1	Sample 1	34		22		21	-37
	Sample 2	31		21		19	-4
Soil 06-A	Desorption [%]
time [h]		2			4	24	48
1/1	Sample 1	21			20	12	-34
	Sample 2	20			17	13	-33

 

Validity criteria fulfilled:

yes

Conclusions:

The arithmetic mean of the adsorption Koc for the three tested soils was determined at 41.36.

Executive summary:

The adsorption/desorption properties of N-Ethylpropylamine were determined in three different soils from European based to OECD guideline 106 (2000).

Tier 1 was performed at a concentration of 5 µg/mL N-Ethylpropylamine in 0.01 M CaCl₂ solution with all five soils at all soil/solution ratios (1/1, 1/2 and 1/5) using the parallel method. Due to the results of Tier1, Tier 2 was performed at a nominal concentration of 5 µg/mL N-Ethylpropylamine in 0.01 M CaCl₂ solution with all five soils at a soil solution ratio of 1/1 using the parallel method. Insignificant adsorption of N-Ethylpropylamine at equilibrium (soil / solution ratio 1/1) was observed (Tier 2 testing) for the soils 2.1 and 2.3. Using the indirect method, the distribution coefficients K_d were calculated and were well below 0.3 mL/g for both soil types and the 1/1 soil/solution ratio used. Therefore, accurate determination of subsequent Freundlich adsorption desorption isotherms are considered not possible and was not performed.

For the soil 2.2, 2.4 and 06-A, the amount of desorption was < 75% of the amount adsorbed within 18 hours, so the adsorption is considered to be irreversible.

The mass balance showed good recovery for the three soils 2.2, 2.4 and 06-A of Tier 3 experiments (average of recovery: 106 – 110 %). The test item was stable during the incubation period of 24 hours adsorption and 18 hours desorption.

The organic carbon normalized Freundlich adsorption coefficient [(µg^(1-1/n))*((cm^3)^1/n)*g^-1)] were 26.4 (Soil 2.2), 32.5 (Soil 2.4), 65.2 (Soil 06-A). The arithmetic mean of the adsorption Koc was 41.36.

The organic carbon normalized Freundlich desorption coefficient [(µg^(1-1/n))*((cm^3)^1/n)*g^-1)] were 254 (Soil 2.2), 9.77 (Soil 2.4), 177 (Soil 06-A).

 

Description of key information

An Adsorption study conducted according to OECD Guideline 106 resulted in an adsorption Koc of 41.36 (mean of three tested soils)

Key value for chemical safety assessment

Koc at 20 °C:

41.36