Tributylethylammonium ethyl sulphate

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:

04 April 2017 - 30 June 2017

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:

2000

Deviations:

yes

Remarks:

see principles below

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.1110 (Activated Sludge Sorption Isotherm)

Version / remarks:

1998

Deviations:

yes

Remarks:

see principles below

Principles of method if other than guideline:

No desorption study was conducted.
The validity criterium of accuracy (i.e. within the range of 70-110%) for the QC samples accompanying the sample analysis of the cation during the kinetics and isotherm tests was not met. Corrections were applied for the cation analyses. With the correction, the adsorption of the cation was relatively low (KF,oc between 67.5 and 1328 mL/g). It can be argued that, without the correction applied, the adsorption of the cation would be even lower. It is therefore decided that the deviation of the guideline does not lead to complete different results. Therefore, the report is considered to be acceptable with the restriction that the results should be viewed as indicative.

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

no

Test temperature:

20 +/- 2 ºC

Analytical monitoring:

yes

Details on sampling:

Analytical runs were performed on April 13, May 01, June 20 (rejected based on QC samples for cation and repeated for anion and cation) and June 30, 2017 (repeat from June 20, 2017) for both anion and cation analysis. On May 19, 2017 an analytical run for anion only was performed.

Matrix no.:

#1

Matrix type:

sandy loam

% Clay:

8

% Silt:

15.8

% Sand:

76.2

% Org. carbon:

1.61

pH:

5.4

CEC:

9.7 meq/100 g soil d.w.

Matrix no.:

#2

Matrix type:

sandy loam

% Clay:

6.5

% Silt:

33.8

% Sand:

59.7

% Org. carbon:

0.67

pH:

5.7

CEC:

7.5 meq/100 g soil d.w.

Matrix no.:

#3

Matrix type:

clay

% Clay:

40.5

% Silt:

34.1

% Sand:

25.4

% Org. carbon:

1.78

pH:

7.2

CEC:

27.3 meq/100 g soil d.w.

Details on matrix:

COLLECTION AND STORAGE
- Geographic location: see specification soils in attached background material
- Sampling depth (cm): no information
- Storage conditions: see specification soils in attached background material
- Storage length: see specification soils in attached background material
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): Sieved (2 mm) air-dried soil samples were taken from storage. Storage was at ambient temperature and did not exceed three years after sampling. Moisture content was determined after oven drying until constant weight.
- When required, the soils were sterilized by autoclaving.
- The moisture content was determined by oven-drying at approximately 105°C for 2 days for the Speyer 2.2, Speyer 2.3 and Speyer 6S soils prior to start of the study. For all calculations the weight of soil was corrected for moisture content. The moisture content of the soils was 1.0% (Speyer 2.2), 0.75% (Speyer 2.3) and 3.9% (Speyer 6S).

Details on test conditions:

TEST CONDITIONS
- Type and further details on reaction vessel:
A preliminary experiment was performed to test the adsorption of test item to container walls and its stability in 0.01 M CaCl2 solution. The amount of test item recovered in the solutions after 24 hours of contact time with the container material in the absence of soil was between 90% and 102% of the nominal concentration in polypropylene vials and between 84% and 99% of the nominal concentration in glass containers. These results indicate that the adsorption of the test item to the container materials is negligible for polypropylene.Therefore, the tests were performed in polypropylene containers.
- Water: Tap water purified by a Milli-Q water purification system
- Temperature: 20 +/- 2 ºC
- pH supernatants after adsorption kinetics anion: 6.8-7.1
pH supernatants after adsorption kinetics cation: 6.7-7.1
pH supernatants after adsorption isotherms anion: 6.2-7.5
pH supernatants after adsorption isotherms cation: 5.9-7.0
- adsorption kinetics: the soils were equilibrated in polypropylene tubes on a roller mixer at 20 +/- 2°C for three days in the dark prior to spiking. One vial per soil per sampling point was prepared. The initial concentration of the test item in the solution was approximately 0.5 mg/L. A blank sample was included for each test system using the same amounts of soil and 0.01 M CaCl2 solution without test item. Two control samples were also included, containing known amounts of 0.01 M CaCl2 solution and spike solution without a test system. The samples were placed on a roller mixer at 20.3 ± 1.2°C in the dark. At the adsorption sampling times (3, 6, 24 and 48 hours), the soil suspensions were removed from the roller
mixer and centrifuged for 5 min at 540 g and 20°C. After centrifugation, a 2 mL aliquot of the supernatant was taken from each sample and added to glass containers. These samples were stored in the freezer (≤ -15°C) until analysis. Blanks and controls were sampled only after 48 hours. At the end of the experiment the pH of the supernatants was determined after decanting.
- adsorption isotherms: Autoclaved soil suspensions (soil:solution ratio of 1:1 for anion determination in Speyer 2.2 and 2.3, 1:2 for anion determination in Speyer 6S and cation determination in Speyer 2.2 and 2.3 and 1:50 for cation determination in Speyer 6S) in glass containers were equilibrated on a roller mixer at 20 ± 2 °C overnight in the dark prior to spiking (duplicate samples per soil and test substance concentration). A blank sample was included for each test system using a known amount of 0.01 M CaCl2 solution and no test substance. Two control samples for each test system were also included, containing known amounts of 0.01 M CaCl2 solution and spike solution but without soil. The adsorption isotherms experiment was initiated by adding the spike volume to the ten pre-equilibrated soil slurries (two replicates per concentration). Initial test item concentrations of approximately 0.05, 0.2, 1, 2 and 5 mg/L were obtained. The samples were incubated on a roller mixer at 20.1 +/- 0.8°C in the dark. After 48 hours of contact time, the soil suspensions were removed from the roller mixer and centrifuged for 15 minutes at 160 g and 20°C. Aliquots of 2 mL of the supernatant were taken from each sample and added to glass containers. These samples were stored in the freezer (≤ -15°C) until analysis. The pH of the supernatants after the adsorption part of the experiment (one replicate of highest and lowest concentration of each test system) was determined.

Duration:

48 h

Initial conc. measured:

ca. 0.5 other: mg/L initally added to the test systems

pH:

7

Temp.:

> 18 - < 22 °C

Remarks:

adsorption equilibrium of cation in non-sterilized test systems and of the anion in sterilized test systems was reached at 48 hours

Sample No.:

#1

Type:

Koc

Value:

67.5 L/kg

pH:

6

Temp.:

20 °C

Matrix:

sandy loam Speyer 2.2

% Org. carbon:

1.6

Remarks on result:

other: Type: organic carbon normalized Freundlich adsorption coefficient

Remarks:

cation

Sample No.:

#2

Type:

Koc

Value:

244 L/kg

pH:

6.4

Temp.:

20 °C

Matrix:

sandy loam Speyer 2.3

% Org. carbon:

0.67

Remarks on result:

other: Type: organic carbon normalized Freundlich adsorption coefficient

Remarks:

cation

Sample No.:

#3

Type:

Koc

Value:

1 328 L/kg

pH:

6.95

Temp.:

20 °C

Matrix:

clay Speyer 6S

% Org. carbon:

1.8

Remarks on result:

other: Type: organic carbon normalized Freundlich adsorption coefficient

Remarks:

cation

Sample No.:

#4

Type:

Kd

Remarks:

anion

Value:

< 0.3 L/kg

pH:

7

Temp.:

20 °C

Matrix:

All

Remarks on result:

other: for all matrices

Remarks:

anion

Adsorption and desorption constants:

See attached background material.

Recovery of test material:

Not performed

Concentration of test substance at end of adsorption equilibration period:

Anion without sterilization: 0.079 mg/L for Speyer 2.2; 0.403 mg/L for Speyer 2.3; 0.285 mg/L for Speyer 6S
Anion with sterilization: 0.417 mg/L for Speyer 2.2; 0.458 mg/L for Speyer 2.3; 0.45 mg/L for Speyer 6S
Cation without sterilization: 0.424 mg/L for Speyer 2.2; 0.393 mg/L for Speyer 2.3; 0.403 mg/L for Speyer 6S

Concentration of test substance at end of desorption equilibration period:

Not performed

Details on results (Batch equilibrium method):

PRELIMINARY TEST
- Sample purity: no correction applied
- Weighed soil and volume of CaCl2 solution: Approximately 30 mL of 0.01 M CaCl2 solution were added to 15 g soil for a soil:solution ratio of 1:2, 45 mL of 0.01 M CaCl2 solution to 4.5 g soil for a ratio of 1:10 and 45 mL of 0.01 M CaCl2 solution to 0.9 g soil for a ratio of 1:50.
- Initial test substance concentration: ca. 0.5 mg/L
- Analytical test substance concentration in final solution: anion: 0.444 - 0.461 mg/L for Speyer 2.2; 0.421 - 0.451 mg/L for Speyer 2.3; 0.352 - 0.433 mg/L for Speyer 6S
cation: 0.270 - 0.495 mg/L for Speyer 2.2; 0.223 - 0.486 mg/L for Speyer 2.3; 0.013 - 0.224 mg/L for Speyer 6S

MAIN TEST: PERFORMANCE
- Test material stability during adsorption phase: see details on analytical methods.
Cation: Stability of the analytical system was proven in all analytical runs throughout the entire calibration curve.
- Experimental conditions maintained throughout the study: Yes
- Degradation of test substance: For the anion, it was observed that soil bioactivity influenced the results in the adsorption kinetics test and thus the test was repeated using sterilized soils.
- Anomalies or problems encountered:
Since adsorption of the anion was extremely low ≤10%, no Freundlich adsorption isotherm parameters could be calculated.
For cation calculations the control samples (spiking solutions without soil) were observed to have significant higher analysed concentration levels than the calculated initial concentration levels, for this reason all adsorption samples were corrected based on this difference.

Validity criteria fulfilled:

yes

Remarks:

Stability of the analytical system was proven in all analytical runs throughout the entire calibration curve

Conclusions:

Adsorption parameters were determined using the batch equilibrium method with three soils in accordance with OECD 106 and GLP principles.
Adsorption kinetics were determined at an initial test item concentration of approximately 0.5 mg/L. Adsorption equilibrium was reached after 48 hours contact time for all three soils. The test item was shown to be stable during the time frame of the experiment for all soils.
Adsorption isotherms were determined over a concentration range from approximately 0.05 to 5 mg/L at a soil:0.01 M CaCl2 solution ratio of 1:1 for anion determination in Speyer 2.2 and 2.3, 1:2 for anion determination in Speyer 6S and cation determination in Speyer 2.2 and 2.3 and 1:50 for cation determination in Speyer 6S. The adsorption isotherms of the cation of the test item could be described by the Freundlich equation. The equilibrium adsorption coefficient (Kd) for the anion was observed to be <0.3 mg/kg and no Freundlich adsorption isotherm parameters could be calculated.
Organic carbon normalized Freundlich adsorption coefficients for the cation were 67.5, 244 and 1328 L/kg for the Speyer 2.2, Speyer 2.3 and Speyer 6S soils, respectively. These values should be considered as indicative as not all validity criteria for the analytical method were met.

Description of key information

Adsorption parameters were determined using the batch equilibrium method with three soils in accordance with OECD 106 and GLP principles. Adsorption kinetics were determined at an initial test item concentration of approximately 0.5 mg/L. Adsorption equilibrium was reached after 48 hours contact time for all three soils. The test item was shown to be stable during the time frame of the experiment for all soils. Adsorption isotherms were determined over a concentration range from approximately 0.05 to 5 mg/L at a soil:0.01 M CaCl2 solution ratio of 1:1 for anion determination in Speyer 2.2 and 2.3, 1:2 for anion determination in Speyer 6S and cation determination in Speyer 2.2 and 2.3 and 1:50 for cation determination in Speyer 6S. The adsorption isotherms of the cation of the test item could be described by the Freundlich equation.

The equilibrium adsorption coefficient (Kd) for the anion was observed to be <0.3 mg/kg. Since adsorption of the anion was extremely low (≤10%), no Freundlich adsorption isotherm parameters could be calculated. Organic carbon normalized Freundlich adsorption coefficients (KFoc) for the cation were 67.5, 244 and 1328 L/kg for the Speyer 2.2, Speyer 2.3 and Speyer 6S soils, respectively. These values should be considered as indicative as not all validity criteria for the analytical method were met.

Key value for assessment:

For the anion, adsorption was extremely low and no KFoc could be calculated. For chemical safety assessment of the anion, it is assumed that no adsorption occurs, and therefore the Koc is set at 1 L/kg which is the minimum value for this parameter in EUSES.

Key value for chemical safety assessment

Koc at 20 °C:

1