2,2'-(octadecylimino)bisethanol

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
See for Read-Across justification chapter 13

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

3 soils tested instead of 5 soils as required in OECD 106

Principles of method if other than guideline:

The number of soils which was used in this test deviates from the recommendation in OECD guideline 106 (2000) in that three soils were used instead of the recommended five soils. The partitioning to soil is not based on a Freundlich isotherm but evaluated based on only one test concentration. These deviations are based on results of earlier adsorption desorption tests with cationic surfactants. The amines in the test substance will to a large extent be protonated under ambient conditions and will therefore interact with the negative surface of mineral particles or with negative charges of humic substances. The ionic interactions play a more important role than hydrophobic partitioning with organic matter. The log Koc is therefore considered as a poor predictor of the partitioning behaviour of cationic surfactants in the environment. These earlier results showed that using three soils with at least one loamy sand and a clay soil, can give as much information as using the full number of soils. These earlier tests also revealed that only rarely linear adsorption isotherms were obtained for cationic surfactants and that extrapolation to lower concentrations based on these non-linear isotherms leads to unrealistic results (e.g. RAR primary fatty amines Oct. 2008). According to the Danish EPA (EPA (http://www.mst.dk/udgiv/publications/2004/87-7614-251-5/html/appd_eng.htm) a more reliable method of extrapolation to lower concentrations, is to use the data originating from the lowest measured concentration and to assume that the coefficient remains constant at lower concentrations. The test as described in this report is therefore performed using only one concentration which is as low as reasonably possible in relation to the detection limit.

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

no

Test temperature:

20 ± 1°C

Details on study design: HPLC method:

EQUIPMENT
- Apparatus: Agilent 1200 HPLC systeem
- Type, material and dimension of analytical (guard) column: LC column Hypersil Gold 2.1 mm * 100 mm, 1.9 µm particle size, Thermoquest
part no 25002-102130
- Detection system: Triple quadrupole MS, Agilent 6410


MOBILE PHASES
HPLC phase A:
To a 2000 ml volumetric flask (in a fume hood):
Add water to approximately ¾ of the volume.
Add 1.3 ml TFA using an Eppendorf Multipette with a 10 ml tip
Add 1.5 ml NH3 (conc, aq) using an Eppendorf Multipette with a 10 ml tip
Add 2.3 ml acetic acid using an Eppendorf Multipette with a 10 ml tip
Fill to the mark with water.

HPLC phase B:
To a flask with at least 2000 ml capacity (in a fume hood):
Add 1 l methanol with a measuring cylinder to the flask.
Add 1.3 ml TFA using an Eppendorf Multipette with a 10 ml tip
Add 1.5 ml NH3 (conc, aq) using an Eppendorf Multipette with a 10 ml tip
Add 2.3 ml acetic acid using an Eppendorf Multipette with a 10 ml tip
Add 1 l 2-propanol to the flask.

- Experiments with additives carried out on separate columns: no

- Solutes for dissolving test and reference substances:
Leaching solution:
Weigh 100 g of MgCl2 * 6 H2O to a 1 l flask.
Add 500 ml of methanol.
Add 500 ml of 2-propanol.
Shake until the salt has dissolved.

REFERENCE SUBSTANCES
- Identity: Internal standard Hexadecylamine-d31


DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 60 µL


REPETITIONS
- Number of determinations: 3

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0.25 - 250 µg/L
- Sample storage before analysis: no

Details on matrix:

Speyer 2.2 soil
Name Speyer standard soil type 2.2 (Sp2.2 1109)
Location "Grosser Striet", Nr.585, Hanhofen, Rheinland-Pfalz, Germany
Sampling date 2009.03.12
Received from Landwirtschaftliche Untersuchungs- und Forschungsanstalt Speyer, Obere Langgasse 40, 67346 Speyer, Germany
Sieved/air dried on March 23, 2009
Storage Received on March 30 from Speyer and further air dried on April 16. Stored at ambient temperature.
Texture (USDA) Loamy sand
pH (0.01 M CaCl2) 5.4 ± 0.1
Organic carbon (%) 2.16 ± 0.40
Particle size distribution % clay (< 2 µm) 6.4 ± 0.9
(USDA) % silt (2-50 µm) 12.2 ± 0.6
% sand (50-2000 µm) 81.4 ± 1.2
CEC (meq/100g) 10 ± 1
Water holding capacity (%) 48.2 ± 5.0

Eurosoil no 4
Name Eurosoil 4. Certified Reference Material IRMM-443-4. No 0034
Location Data can be obtained from IRMM
Sampling date Data can be obtained from IRMM
Received from EC-JRC-IRMM, Unit for Reference Materials, Retieseweg 111, 2440 Geel, Belgium
Sieved/air dried on Data can be obtained from IRMM
Storage Received on March 17 from Speyer . Stored at ambient temperature.
Texture (USDA) Silt
pH (0.01 M CaCl2) 6.8 ± 0.6
Organic carbon (%) 1.31
Particle size distribution % clay (< 2 µm) 20.3
(USDA) % silt (2-50 µm) 75.7
% sand (50-2000 µm) 4.1
CEC (meq/100g) 17.3
Water holding capacity (%) Data can be obtained from IRMM

Speyer 6S soil
Name Speyer standard soil type 6S (Speyer 6S 0809)
Location "In der unteren Hohnert", Nr.3412, Siebeldingen, Rheinland-Pfalz, Germany
Sampling date 2009-02-18
Received from Landwirtschaftliche Untersuchungs- und Forschungsanstalt Speyer, Obere Langgasse 40, 67346 Speyer, Germany
Sieved/air dried on February 26, 2009
Storage Received on March 30 from Speyer and further air dried on April 16. Stored at ambient temperature.
Texture (USDA) Clay
pH (0.01 M CaCl2) 7.2 ± 0.1
Organic carbon (%) 1.75 ± 0.11
Particle size distribution % clay (< 2 µm) 42.1 ± 1.8
(USDA) % silt (2-50 µm) 36.0 ± 2.3
% sand (50-2000 µm) 21.9 ± 1.6
CEC (meq/100g) 22 ± 6
Water holding capacity (%) 40.7 ± 5.0

Details on test conditions:

TEST CONDITIONS
- pH: see results
- Suspended solids concentration: 1:100


TEST SYSTEM
- Type, size and further details on reaction vessel: Glass containers 40 mL with teflon lined caps, suitable for centrifugation at 3000*g
- Water filtered (i.e. yes/no; type of size of filter used, if any): Purified water, Milli-Q, Millipore, Bedford, MA, USA
- Amount of soil/sediment/sludge and water per treatment (if simulation test): 250 mg soil + 24.9 mL CaCl2 solution + 100 µL test substance dissolved in MeOH
- Soil/sediment/sludge-water ratio (if simulation test): 1:100
- Number of reaction vessels/concentration: 3
- Measuring equipment: Metrohm 704 pH Meter, Analytical balance with 0.1 mg accuracy
- Test performed in closed vessels due to significant volatility of test substance: yes
- Method of preparation of test solution:
About 250 mg soil (Speyer 2.2 and 6S) and 24.9 mL of 0.01 M CaCl2 solution was equilibrated in a capped glass centrifugation tube on a shaker at 20 ± 1°C during one night in the dark prior to spiking. pH was measured before adding spiking. The test, conducted in triplicate for each soil, was started by adding 100 µL of spike solution to the pre-equilibrated soil slurries, giving a final concentration of approximately 1 mg/L

Sample No.:

#1

Duration:

24 h

Initial conc. measured:

2 other: *10^3 cm3/g

pH:

5.4

Temp.:

20 °C

Sample No.:

#2

Duration:

24 h

Initial conc. measured:

4.6 other: *10^3 cm3/g

pH:

6.8

Temp.:

20 °C

Sample No.:

#3

Duration:

24 h

Initial conc. measured:

4.5 other: *10^3 cm3/g

pH:

7.2

Temp.:

20 °C

Sample no.:

#1

Duration:

48 h

Conc. of adsorbed test mat.:

5.8 other: *10^3 cm3/g

Temp.:

20 °C

Sample no.:

#2

Duration:

48 h

Conc. of adsorbed test mat.:

11.3 other: *10^3 cm3/g

Temp.:

20 °C

Sample no.:

#3

Duration:

48 h

Conc. of adsorbed test mat.:

4.5 other: *10^3 cm3/g

Temp.:

20 °C

Type:

Kd

Value:

2 025

Temp.:

20 °C

% Org. carbon:

2.16

Remarks on result:

other: Speyer 2.2

Type:

Kd

Value:

4 639

Temp.:

20 °C

% Org. carbon:

1.75

Remarks on result:

other: Speyer 6S

Type:

Kd

Value:

4 526

Temp.:

20 °C

% Org. carbon:

1.31

Remarks on result:

other: Eurosoil 4

Details on results (HPLC method):

Linearity: All individual calibration curves were found to be quadratic with a regression value R2 > 0.99

Selectivity/specificity: The selectivity and specificity of the method is assured by using MRM parameters


Detection and Quantification Limit

The detection limit (LOD) is estimated by comparing blank samples with standards.
Component Quantification Detection
limit limit
C16’ 2EO 0.2 µg/l 0.1 µg/l
C18’ 2EO 0.2 µg/l < 0.2 µg/l
C18’’ 2EO 0.1 µg/l 0.02 µg/l
Tentative 0.5 µg/l 0.3 µg/l
total value

Accuracy
The accuracy is calculated from performed recovery experiments
Matrix Spiked mass Corresponding Recovery
conc. in sample
DSW 40 ng 2 µg/l 79 % (73, 84)

Adsorption and desorption constants:

- Adsorption and desorption coefficients (Kd):

Soil type Component Replicate Kd Koc Kdes
(103 cm3/g) (104 cm3/g) (103 cm3/g)


Speyer 2.2 C16’ A 0.694 2.96 1.84
B 0.916 3.91 1.31
C 0.722 3.08 1.66
C18’’ A 1.10 4.70 4.55
B 2.10 8.95 2.80
C 1.19 5.08 4.15
C18’ A 1.45 6.18 9.76
B 4.56 19.5 4.53
C 1.56 6.65 8.82
Speyer 6s C16’ A 1.39 7.48 3.88
B 2.59 13.9 5.08
C 1.34 7.19 6.86
C18’’ A 2.01 10.8 5.01
B 5.27 28.3 8.12
C 1.71 9.22 12.3
C18’ A 2.63 14.1 4.41
B 13.4 72.2 10.6
C 2.23 12.0 25.2
Eurosoil 4 C16’ A 1.81 13.7 1.07
B 0.917 6.93 1.54
C 1.35 10.2 1.47
C18’’ A 2.34 17.7 1.69
B 1.92 14.5 3.46
C 2.95 22.3 3.13
C18’ A 6.45 48.7 2.91
B 4.74 35.9 8.73
C 7.83 59.2 6.49

Recovery of test material:

Analyte Replicate Added test Amount found Amount des. Recovery Adsorption to
substance in water from glass (total) glass container
(µg) (µg) (µg) (%) (%)

C16’ A 1.82 1.361 0.042 77.0 2.3
B 1.82 1.362 0.065 78.3 3.6
C 1.82 1.446 0.030 80.9 1.7
C18’’ A 2.34 1.609 0.140 74.6 6.0
B 2.34 1.540 0.214 74.8 9.1
C 2.34 1.686 0.110 76.6 4.7
C18’ A 21.88 11.644 3.762 70.4 17.2
B 21.88 9.872 5.496 70.2 25.1
C 21.88 12.364 3.220 71.2 14.7

Concentration of test substance at end of adsorption equilibration period:

The nominal initial concentration in the aqueous phase was 1 mg/L
The equilibrium concentrations in the aqueous phase range from:
56 - 137.5 µg/L for Speyer 2..2, which equals 93.7% adsorption
20 - 89 µg/L for Speyer 6S, which equals 96.2% adsorption
34.8 - 56.3 µg/L for Eurosoil 4, which equals 97.1% adsorption

Speyer 2.2
Replicate Amount test subst. (µg)
in water from container wall adsorbed on soil
A 3.4383 0.4244 44.64
B 1.3977 0.3791 46.72
C 3.1655 0.3662 44.97

Speyer 6S
Replicate Amount test subst. (µg)
in water from container wall adsorbed on soil
A 1.9553 0.2359 46.31
B 0.5058 0.2611 47.71
C 2.2228 0.2758 46.00

Eurosoil 4
Replicate Amount test subst. (µg)
in water from container wall adsorbed on soil
A 0.6259 0.2477 47.27
B 1.4068 0.3989 46.69
C 0.8702 0.2640 47.37

Concentration of test substance at end of desorption equilibration period:

Amount test substance in water (µg)

Replicate Speyer 2.2 Speyer 6S Eurosoil 4
A 0.6555 1.0879 1.9256
B 1.2638 0.5108 0.7953
C 0.7136 0.2422 0.9601

Validity criteria fulfilled:

yes

Conclusions:

The observed Kd values increases with increased CEC values for the three soils, see Table.

Executive summary:

The Adsorption/desorption study was performed according to OECD 106 using three soils with different organic carbon content and CEC value. The observed distribution coefficient is the most important value for cationic surfactants like the current tested material. It is determined that the distribution coefficient for the different soil types increases with increased CEC value of the soils. No relationship with the corresponding organice carbon content of the soils has been observed.

Results of all 3 tested soils

Soil	Clay (%)	Silt (%)	Sand (%)	CEC (meq/100g)	pH	Org C (%)	Caq (µg/l)	Kd (10^3cm^3/g)	Koc (10^4cm^3/g)
Speyer2.2	6.4	12.2	81.4	10	5.4	2.16	107	2.0	8.6
Eurosoil 4	20.3	75.7	4.1	17.3	6.8	1.31	43	4.5	34
Speyer6S	42.1	36.0	21.9	22	7.2	1.75	62	4.6	25

Description of key information

A refined sorption/desorption test according to OECD 106 with 2,2’-(Octadec-9-enylimino) -bisethanol (CAS No 25307-17-9) resulted in equilibrium constants (Kd's) of 2025, 4526 and 4639 L/kg for loamy sand, silt and clay soil. As there is no direct relationship with the sorption behaviour of the substance and the organic carbon content of the soil because other soil properties like the Cation Exchange Capacity and the pH are more important to predict the sorption behaviour, no Koc's are given.

Despite of that mainly for practical reasons a Koc is calculated from this Kd applying the non-hydrophobics QSAR according to the (TGD, 2003). This Koc can be used to predict the sorption in other compartments than soil and sediment e.g. with a low CEC.

Key value for chemical safety assessment

Koc at 20 °C:

90 520

Other adsorption coefficients

Type:

log Kp (solids-water in soil)

Value in L/kg:

3.66

at the temperature of:

20 °C

Other adsorption coefficients

Type:

log Kp (solids-water in sediment)

Value in L/kg:

3.66

at the temperature of:

20 °C

Other adsorption coefficients

Type:

log Kp (solids-water in suspended matter)

Value in L/kg:

3.957

at the temperature of:

20 °C

Additional information

Due to the cationic surface-active properties will primary fatty amine ethoxylates adsorb strongly onto the solid phase of soil and sediments. These substances can adsorb both onto the organic fraction and, dependent on the chemical composition, onto the surface of the mineral phase, where sodium and potassium ions can be exchanged against the alkyl ammonium ion. The determination of a Koc from log Kow is not opportune, because the common equations for Koc derivation are not valid for both ionic and surface active substances.

 

The adsorption behaviour of primary fatty amine ethoxylates was assessed using 2,2’-(Octadec-9-enylimino) -bisethanol (CAS No 25307-17-9) as a worst-case representative of this category. The adsorption/desorption was studied in a batch equilibrium experiment according to a refined OECD 106 (Farnback, 2010). Three soils were used, encompassing a range of clay and organic matter. The test substance adsorbed partially onto the container walls which was considered for the determination of the adsorption coefficients. Adsorption kinetics was determined by measurements at different sampling times (up to 24 h), an equilibrium was reached after 3 hours. Desorption occurred to a lesser extent than adsorption. The table below presents a summary of the most important soil properties and observed partitioning constants.

Table1. Overview of soil properties of soils used for the sorption test and distribution coefficients observed for 2,2’-(Octadec-9-enylimino) -bisethanol (CAS No 25307-17-9)

Soil	Clay (%)	Silt (%)	Sand (%)	CEC (meq/100g)	pH	Org C (%)	Caq (µg/l)	Kd (10^3cm^3/g)	Koc (10^4cm^3/g)
Speyer2.2	6.4	12.2	81.4	10	5.4	2.16	107	2.0	8.6
Eurosoil 4	20.3	75.7	4.1	17.3	6.8	1.31	43	4.5	34
Speyer6S	42.1	36.0	21.9	22	7.2	1.75	62	4.6	25

From the results it can be observed that the sorption onto Speyer 6S (clay soil) is much higher than to Speyer 2.2 (loamy sand) despite of the higher organic matter content in the Speyer 2.2 soil. This can be explained that ionic interactions play a more important role than hydrophobic partitioning with organic matter. Alkyl ammonium ions can interact with the surface of mineral particles or with negative charges of humic substances. The influence of the chain length on the sorption behaviour is therefore expected to be less important and the experimental results obtained in the test with 2,2’-(Octadec-9-enylimino) -bisethanol can therefore be taken as a worst-case for other ethoxylated amines with equal or shorter alkyl chain lengths.

The number of soils which was used in this test deviates from the recommendation in OECD guideline 106 (2000) in that three soils were used instead of the recommended five soils. In addition is the partitioning to soil is not based on a Freundlich isotherm but evaluated based on only one test concentration. These deviations are based on results of earlier adsorption desorption tests with cationic surfactants. The ammonium ions will interact with the negative surface of mineral particles or with negative charges of humic substances. The ionic interactions play a more important role than hydrophobic partitioning with organic matter. The log Koc (alone) is therefore considered as a poor predictor of the partitioning behaviour of cationic surfactants in the environment. These earlier results showed that using three soils with at least one loamy sand and a clay soil, can give as much information as using the full number of soils. These earlier tests also revealed that only rarely linear adsorption isotherms were obtained for cationic surfactants and that extrapolation to lower concentrations based on these non-linear isotherms leads to unrealistic results (e. g. RAR primary fatty amines Oct. 2008). According to the Danish EPA (http: //www. mst. dk/udgiv/publications/2004/87-7614-251 -5/html/appd_eng. htm) a more reliable method of extrapolation to lower concentrations, is to use the data originating from the lowest measured concentration and to assume that the coefficient remains constant at lower concentrations. The test as described is therefore performed using only one concentration which is as low as reasonably possible in relation to the detection limit.

The initial concentration used for the determination of the soil partitioning constant was 1 mg/L. The observed aquatic equilibrium concentrations in the experiment range from 20 to 138 µg/L.

For the prediction of the partitioning of the 2,2’-(Octadec-9-enylimino) –bisethanol in soil, sediment and suspended matter not the K_d based on organic matter (Koc) will be used but the uncorrected K_d because the relation between the organic matter concentration alone and the sorption observed is not sufficient. Research sponsored by APAG CEFIC was performed on these difficult substances at UFZ (K. U. Goss, S. Droge) and IRAS (J. Hermens) to improve the knowledge on bioavailability and partitioning to soil and sediment.

Because there is no principal difference between soil and sediments considering the sorption properties and because for cationic surfactants the degree of sorption is not directly related to the organic carbon content, the Kd value for soil will also be used for sediment and suspended particles. For sludge which consists mainly of organic matter the sorption data as observed for soil is not considered to be representative. This is however not a serious problem because the removal by sorption in a waste water treatment plant will be close to what is observed in the waste water treatment simulation test i. e. 0.16% removal.

Despite of that mainly for practical reasons (e. g. in the exposure models) a Koc is calculated from this Kd applying the non-hydrophobics QSAR according to the (TGD, 2003). This Koc of 90520 L/kg can be used to predict the sorption in other compartments than soil and sediment.

In the table below the distribution constants used in this assessment is summarized:

Distribution constants to be used for 2,2'-(octadec-9-enylimino) bisethanol

Kpsoil		4526 L^.kg^-1		Ksoil-water		6792 m^3.m^-3
Kpsusp		9052 L^.kg^-1		Ksusp-water		2264 m^3.m^-3
Kpsed		4526 L^.kg^-1		Ksed-water		2264 m^3.m^-3

 

With a Kp_susp  of 9052 L/kg and a concentration of 15 mg/L suspended matter in surface waters, the adsorbed fraction is calculated as 12%.

 

[LogKoc: 4.95]