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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017-02-20 to 2017-05-15
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Version / remarks:
Samples were centrifuged < 3000 g because glass vessels had to be used. Higher centrifugation forces could have been destructive to these vials.
For the adsorption isotherms, the use of a concentration range in the order of two magnitudes was not feasible. With regard to the limit of quantification, relativelyhigh test item concentrations were required when using a soil solution ratio of 1 g soil to 100 mL of aqueous phase. The non-linearity of the adsorption is already observed at the concentration range used, as can be seen by the 1/n values.
Limited stability of the test item in 0.01 M CaCl2 solution was observed, which is presumably related to the chemical structure of the test item and the formation of metal complexes with Ca2+. Therefore, adaptions of the test system were necessary and demineralized water was used as aqueous medium.

These deviations are considered to have no impact on the quality and the integrity of the study.
Deviations:
yes
Remarks:
see above at "Version / remarks"
Qualifier:
according to
Guideline:
other: Council Regulation (EC) No. 440/2008, Method C.18 (2008)
GLP compliance:
yes (incl. certificate)
Type of method:
batch equilibrium method
Media:
soil
Radiolabelling:
no
Test temperature:
Nominal: 20 ± 2 °C
Analytical monitoring:
yes
Details on sampling:
Medium: CaCl2-solutionwas used during Tier 1. Deionised water was used to prepare the CaCl2 solution (0.01 M).
Deionised water was used during Tier 2 and Tier 3.

Soil / Solution ratio: 1:100

Agitation: By horizontal shaker. Frequency was adjusted to avoid sedimentation of soil particles during treatment.

Test temperature: 20 +/- 2 °C

Test Procedure:

Test vessels: Disposable glass bottles (120 mL)
Concentration for adsorption / desorption experiments: Tier 2: 7.00 mg/L; Tier 3: 3.00 mg/L, 16.5 mg/L, 23.5 mg/L, 30.0 mg/L

Stock solutions: Stock solutions of Sodium oleylamphopolycarboxyglycinate were prepared in HPLC water and stored at room temperature.


Preparation

Preparation of the Soil samples (conditioning):
The soils were weighed into the test vessels and an appropriate volume of 0.01 M CaCl2 solution or test medium was added. After agitation overnight (12 h minimum), the samples were used for adsorption experiments.

Preparation of the samples for adsorption experiments:
The soil samples were conditioned as described above. 0.1 volume-% of the stock solutions, related to the volume of the
aqueous phase in the soil suspensions was added in order to adjust the test concentrations. Afterwards, the samples were agitated.

Preparation of the samples for desorption experiments:
Test vessels from the adsorption experiments were used for this purpose. After completion of the adsorption experiments the test vessels were centrifuged, weighed and the supernatant was replaced by fresh test medium. Then the test vessels were agitated again to investigate the desorption behavior of the test item.

Preparation of samples for analysis:
The soil suspensions were centrifuged at 3000 rpm (2504 g) after agitation to separate the phases, followed by analysing the concentration of the main component of Sodium oleylamphopolycarboxyglycinate in aqueous phase by LC-MS/MS. For analysis of the soil, the aqueous phase was decanted and the soil was extracted. Extracts were also analysed by LC-MS/MS.

Replicates: All samples were prepared in duplicate.

Controls:
CaCl2 solution or test medium was conditioned as described above, followed by separation of the aqueous phase by centrifugation. Then the aqueous phase was fortified acc. to the concentrations used for the test item samples to verify the stability of the test item in the aqueous phase under test conditions. The samples were agitated as long as the test item sample with the longest agitation period.
Additional control replicates were prepared during Tier 1 without conditioning the CaCl2 solution prior to spiking. Samples without conditioning were prepared for comparison of the test item stability with and without soil-conditioning (e.g. different ionic environment and pH value).

Replicates: Duplicates

Blank:
Blank samples were prepared for all soils as described for the test item samples but without fortification with the test item. The samples were agitated as long as the samples with the longest agitation period.

Replicates: Duplicates (Tier 1), single (Tier 2 and Tier 3)

Sample Preparation:

Dilution medium: 2-Propanol / matrix-conditioned demineralized water (50:50)

Standards:
Stock solutions of 10 g/L of the test item in HPLC water were prepared and were diluted to calibration standards.
Tier 1: 8 calibration standards in the range of 50 to 1000 µg/L were prepared using methanol : HPLC water (50 : 50).
Tier 2 and Tier 3: 8 calibration standards in the range of 50 to 1000 µg/L were prepared using dilution medium.

Aqueous phase:
Samples were centrifuged at 3000 rpm (2504 g) for 5 min. An aliquot of each aqueous sample was stabilized by dilution with 2-propanol or methanol during Tier 1 (factor 2). Samples were diluted to calibration range with dilution medium, if necessary.

Test vessel adsorption
After sampling of the aqueous phase, the test vessels were emptied and rinsed with 0.01 M CaCl2. 2-Propanol was used for extraction of the test item from the test vessel. Therefore, the vessel was shaken by hand for 1 min, ultrasound was used for 5 min and the vessel was shaken 20 min on a shaker. 0.01 M CaCl2 was used if dilution factor 2 was needed, dilution medium for further dilutions to calibration range, if necessary.

Soil extraction:
After decantation of the aqueous phase, the soil was used for extraction. The wet soil was extracted by using an accelerated solvent extractor (ASE) and was weighed into a solvent extractor cell (approx. 1 g dry weight). To each sample, 2 g magnesium chloride hexahydrate and 4 g silica gel were added and homogenised carefully with the soil. Then, the samples were extracted with 2-propanol : HPLC water (50 : 50). For parameters of the extraction method see below. Extracts were transferred quantitatively into a 100 mL measuring flask and filled up with 2-propanol : HPLC water (50 : 50). Aliquots were diluted with 2-propanol : HPLC water (50 : 50) to calibration range.

Parameters of the extraction method:
Preheat: 1 min
Heat: 6 min
Static: 10 min
Flush: 50 % (v/v)
Purge: 90 sec
Cycles: 3
Pressure: 1500 psi
Temperature: 125 °C
Solvent: 2-propanol : HPLC water (50 : 50)

Samples for method validation:
Samples were prepared as described above (‘soil samples (conditioning)’). The aqueous phases were decanted and spiked with test item at 1 x LOQ level. Blank samples were prepared accordingly but without spiking with test item. Samples were diluted with 2-propanol by a factor 2.

Sample storage: All samples were stored at room temperature prior and after analysis.
Matrix no.:
#1
Matrix type:
loamy sand
% Clay:
8.5
% Silt:
11.3
% Sand:
80.2
% Org. carbon:
1.47
pH:
5.4
CEC:
7.6 meq/100 g soil d.w.
Matrix no.:
#2
Matrix type:
clay loam
% Clay:
25.2
% Silt:
42.3
% Sand:
32.6
% Org. carbon:
1.74
pH:
7.4
CEC:
22 meq/100 g soil d.w.
Matrix no.:
#3
Matrix type:
loamy sand
% Clay:
10.2
% Silt:
31.1
% Sand:
58.7
% Org. carbon:
0.916
pH:
7.3
CEC:
10 meq/100 g soil d.w.
Matrix no.:
#4
Matrix type:
other: Dystric Cambisol
% Clay:
17
% Silt:
36.8
% Sand:
46.4
% Org. carbon:
3.01
pH:
5.5
CEC:
16.6 meq/100 g soil d.w.
Matrix no.:
#5
Matrix type:
Luvisol
% Clay:
20.3
% Silt:
75.7
% Sand:
4.1
% Org. carbon:
1.31
pH:
6.8
CEC:
17.3 meq/100 g soil d.w.
Details on matrix:
Relevant Characteristics of Soils for Adsorption / Desorption

Soil Parameter LUFA 2.2 LUFA 2.4 LUFA 5M Eurosoil 3 Eurosoil 4
Soil type (LUFA Soils) 1) Loamy sand Clayey loam Loamy sand
FAO soil unit (Eurosoils) 2) Dystric Cambisol Orthic Luvizol
pH (0.01 M CaCl2) 5.4 3) 7.4 3) 7.3 3) 5.5 5) 6.8 5)
Organic Carbon [%] 1.47 4) 1.74 4) 0.916 4) 3.01 5) 1.31 5)
Clay (< 0.002 mm) [%] 8.5 4) 25.2 4) 10.2 4) 17.0 2) 20.3 2)
Silt (0.002-0.063 mm) [%] 11.3 4) 42.3 4) 31.1 4) 36.8 2) 75.7 2)
Sand (0.063-2 mm) [%] 80.2 4) 32.6 4) 58.7 4) 46.4 2) 4.1 2)
Cation exchange capacity [mval/100 g] 7.6 4) 22 4) 10 4) 16.6 2) 17.3 2)
1) according to German DIN
2) data taken from Gawlik and Muntau, Eurosoils II Laboratory and Reference Materials for Soil-related Studies, Environment Institute 1999
3) data obtained from LUFA Speyer, analysis data sheet from 2016-03-15
4) determined externally at AGROLAB GMBH (non-GLP)
5) values taken from soil certificates

Origin of soils:
Landwirtschaftliche Untersuchungs- und Forschungsanstalt LUFA Speyer, Obere Langgasse 40, 67346 Speyer, Germany

European Commission, Joint Research Centre, Institute for Reference Materials and Measurements IRMM Retieseweg, B-2440 Geel, Belgium


Storage at test facility: Room temperature, in closed containers


Date of receipt:
LUFA 2.2 (batch: F2.24016): 2016-10-24
LUFA 2.4 (batch: F2.44116): 2016-10-24
LUFA 5M (batch: F5M5015): 2016-12-17
Eurosoil 3 (IRMM-443-3 batch: 102): 2016-09-27
Eurosoil 4 (IRMM-443-4 batch: 27): 2017-03-09

Expiry date:
According to test facility standard operation procedure, the expiry date was set to five years after receipt of the soils.
LUFA 2.2 (batch: F2.24016): 2021-10-24
LUFA 2.4 (batch: F2.44116): 2021-10-24
LUFA 5M (batch: F5M5015): 2021-12-17
Eurosoil 3 (IRMM-443-3 batch: 102): 2021-09-27
Eurosoil 4 (IRMM-443-4 batch: 27): 2022-03-09

Characterization date:
LUFA soils were characterized in relation to their organic carbon content and cation exchange capacity externally at Agrolab GmbH.
LUFA 2.2 (batch: F2.24016): 2017-02-13
LUFA 2.4 (batch: F2.44116): 2017-02-13
LUFA 5M (batch: F5M5015): 2017-02-13

Key result
Sample No.:
#1
Phase system:
soil-water
Type:
other: Koc
Value:
63 732 L/kg
Temp.:
20 °C
pH:
6.7
Matrix:
LUFA 2.2
% Org. carbon:
1.47
Remarks on result:
other: Koc at 7 mg/L
Remarks:
Concentration in water at equilibrium: 290 ug/L
Sample No.:
#1
Phase system:
soil-water
Type:
other: Koc Fads
Remarks:
From Freundlich isotherm
Value:
56 689 L/kg
Temp.:
20 °C
pH:
6.7
Matrix:
LUFA 2.2
% Org. carbon:
1.47
Key result
Sample No.:
#2
Phase system:
soil-water
Type:
other: Koc
Value:
98 867 L/kg
Temp.:
20 °C
pH:
8.4
Matrix:
LUFA 2.4
% Org. carbon:
1.74
Remarks on result:
other: Koc at 7 mg/L
Remarks:
concentration in water at equilibrium: 166 ug/L
Sample No.:
#2
Phase system:
soil-water
Type:
other: Koc fads
Remarks:
from Freundlich isotherm
Value:
68 742 L/kg
Temp.:
20 °C
pH:
8.4
Matrix:
LUFA 2.4
% Org. carbon:
1.74
Key result
Sample No.:
#3
Phase system:
soil-water
Type:
other: Koc at 7 mg/L
Value:
20 765 L/kg
Temp.:
20 °C
pH:
8.8
Matrix:
LUFA 5M
% Org. carbon:
0.916
Remarks on result:
other: Concentration in water at equilibrium 1015 ug/L
Sample No.:
#3
Phase system:
soil-water
Type:
other: Koc Fads
Remarks:
Freundlich isotherm Koc
Value:
19 464 L/kg
Temp.:
20 °C
pH:
8.8
Matrix:
LUFA 5M
% Org. carbon:
0.916
Key result
Sample No.:
#4
Phase system:
soil-water
Type:
other: Koc at 7 mg/L
Value:
31 279 L/kg
Temp.:
20 °C
pH:
7
Matrix:
Eurosoil 3
% Org. carbon:
3.01
Remarks on result:
other: Concentration in water at equilibrium 276 ug/L
Sample No.:
#4
Phase system:
soil-water
Type:
other: Koc Fads
Remarks:
Freundlich isotherm Koc
Value:
20 925 L/kg
Temp.:
20 °C
pH:
7
Matrix:
Eurosoil 3
% Org. carbon:
3.01
Key result
Sample No.:
#5
Phase system:
soil-water
Type:
other: Koc at 7 mg/L
Value:
203 597 L/kg
Temp.:
20 °C
pH:
7.9
Matrix:
Eurosoil 4
% Org. carbon:
1.31
Remarks on result:
other: Concentration in water at equilibrium 261 ug/L
Sample No.:
#5
Phase system:
soil-water
Type:
other: Koc Fads
Remarks:
Freundlich isotherm Koc
Value:
150 645 L/kg
Temp.:
20 °C
pH:
7.9
Matrix:
Eurosoil 4
% Org. carbon:
1.31
Concentration of test substance at end of adsorption equilibration period:
24 hours equilibrium time with 7 mg/L starting concentration with a soil/solution ratio of 1/100:
Soil #1: LUFA 2.2: 290 µg/L
Soil #2: LUFA 2.4: 166 µg/L
Soil #3: LUFA 5M: 1015 µg/L
Soil #4: Eurosoil 3: 276 µg/L
Soil #5: Eurosoil 4: 261 µg/L

Temperature: The temperature was in the range of 20 ± 2 °C during the course of the studie.

Dry Weights: The dry weight of each solid matrix was determined.

 

Soil Dry Weights Mean values (n = 3)

 

Soil type

LUFA 2.2

LUFA 2.4

LUFA 5M

Eurosoil 3

Eurosoil 4

soil dry weight [%]

92.8

92.9

93.2

97.7

96.9

 pH Values:

The pH values of the aqueous media of the test systems were measured before and after equilibration with the corresponding soils and after addition of the test item in the highest test item concentration. Results are shown in the following table.

 

 pH Values of the Aqueous Media Soil / solution ratio 1:100

 

Soil type

LUFA 2.2

LUFA 2.4

LUFA 5M

Eurosoil 3

Eurosoil 4

demineralized water

7.1

7.1

7.1

7.8

7.8

after soil contact

7.2

8.5

8.4

6.9

7.1

after addition of the test item

6.7

8.4

8.8

7.0

7.9

 Results of Tier 1:

DuringTier 1 experiments have been conducted to find the optimal matrix / solution ratio and the time to reach equilibrium for each matrix. Therefore, the amount adsorbed at equilibrium was determined. In addition, test item stability was demonstrated by measuring test item control samples with conditioned CaCl2 solution but without soil and test item control samples without conditioning with soil during the experiments. The mass balance was evaluated.

 

Adsorption Experiments using 0.01 M CaCl2

Experiments have been conducted in LUFA soils 2.2 and 2.4 using a soil / solution ratio of 1:100. Samples were taken after 4, 24 and 48 hours and the aqueous phase was analysed.

Adsorption of ≥ 94% was already observed after 4 h. In addition, solubility was visually determined in aqueous solutions. The solubility is high in demineralized water (demin.) but when CaCl2 0.01 M is used, precipitation occurred (visually confirmed). The test item can be redissolved if the pH value is increased. If the solution in demin. is acidified, precipitation is observed as well. Based on these observations, sodium hydroxide was added to the test item control samples at the end of the experiment to demonstrate that the low recovery observed was caused by precipitation of the test item. Addition of sodium hydroxide and thereby increase of the pH value led to a recovery improvement from 73% to 90% for LUFA 2.2. The solubility of the test substance in the test system is therefore considered to be dependent on pH and the calcium cations in the aqueous solution. In addition, un-conditioned 0.01 M CaCl2 was used for additional test item control samples. The results observed were comparable. Recovery rates of 58% and 51% were obtained prior to adding sodium hydroxide.


 Tier 1:Adsorption Experiments LUFA 2.2 1:100
Applied test item concentration: 10000 µg/L, n=2

Sampling point

 

 

[h]

Adsorption

 

 

 

[%]

Recovery rate of un-conditioned control
pH = 6.4
[%]

Recovery rate of un-conditioned control after addition of NaOH

[%]

Recovery rate of conditioned control
pH = 6.5
[%]

Recovery rate of conditioned control after addition of NaOH

[%]

0

-

99

-

86

-

4

94

-

-

-

-

24

96

-

-

-

-

48

96

58

85

73

90

-                 not determined

 

Tier 1:Adsorption Experiments LUFA 2.4 1:100
Applied test item concentration: 10000 µg/L, n=2

Sampling point

 

 

[h]

Adsorption

 

 

 

[%]

Recovery rate of un-conditioned control
pH = 6.4
[%]

Recovery rate of un-conditioned control after addition of NaOH

[%]

Recovery rate of conditioned control
pH = 7.5
[%]

Recovery rate of conditioned control after addition of NaOH

[%]

0

-

97

-

90

-

4

98

-

-

-

-

24

> 981)

-

-

-

-

48

> 981)

51

106

92

87

1)               measured concentration of aqueous phase was lower than the lowest calibration level

-                 not determined

The lower recovery in CaCl2 solution (conditioned and un-conditioned) can be presumably attributed to the calcium binding to the chelating part of the molecule and consequently precipitation of the test item calcium complex.

By increasing the pH, calcium is replaced by sodium and the sodium complex is apparently better soluble. Since the precipitation of the test item is also expected to occur in the test vessels with soil, this would result in an overestimation of the fraction sorbed.


 

Test Item Stability in the Aqueous Phase and Test Vessel Adsorption

Since CaCl2 should be added to the test medium to mimic environmental conditions, stability of test item control samples was additionally investigated in 0.001 M CaCl2 solution and 0.01 M NaCl solution.

Sodium was used instead of calcium since the solubility of the sodium complex is apparently higher than the calcium complex. Solubility/ stability was compared in 0.01 M CaCl2solution, 0.001 M CaCl2solution, 0.01 M NaCl solution and also demineralized water.

 

Tier 1:Stability in Test Item Control Samples of LUFA 2.2 – 1 mg/L

Soil / solution ratio 1:100, test item concentration 1 mg/L, n=2

Matrix

pH after addition of test item

Sampling point

[h]

Recovery rate1)

[%]

0.01 M CaCl2(un-conditioned)

7.4

0

85

4

70

24

47

0.01 M CaCl2conditioned

7.0

0

105

4

50

24

32

0.001 M CaCl2(un-conditioned)

6.8

0

102

4

73

24

59

0.001 M CaCl2conditioned

7.2

0

84

4

80

24

61

0.01 M NaCl (un-conditioned)

-

0

66

4

76

24

35

0.01 M NaCl conditioned

7.3

0

64

4

91

24

69

demin. (un-conditioned)

7.8

0

99

4

70

24

87

demin. conditioned

7.8

0

89

4

85

24

68

1)         recovery from nominal concentration at 0h, recovery rate from initially measured concentration at 4 h and 24 h

2)         one replicate shown, second replicate not taken into account

-          not determined


 Tier 1:Stability in Test Item Control Samples of LUFA 2.2 – 10 mg/L

Soil / solution ratio 1:100, test item concentration 10 mg/L, n=2

Matrix

pH after addition of test item

Sampling point

[h]

Recovery rate1)

[%]

0.01 M CaCl2(un-conditioned)

7.1

0

86

4

43

24

30

0.01 M CaCl2conditioned

7.1

0

108

4

40

24

26

0.001 M CaCl2(un-conditioned)

-

0

123

4

74

24

51

0.001 M CaCl2conditioned

-

0

130

4

74

24

53

0.01 M NaCl (un-conditioned)

-

0

110

4

86

24

69

0.01 M NaCl conditioned

-

0

118

4

95

24

78

demin. (un-conditioned)

8.1

0

105

4

80

24

75

demin. conditioned

7.9

0

98

4

91

24

80

1)     recovery from nominal concentration at 0 h, recovery rate from initially measured concentration at 4 h and 24 h

-       not determined

 

After 24 h, the test vessels of the 10 mg/L samples of conditioned matrices were rinsed with sodium hydroxide solution to redissolve the precipitated substance from test vessel walls. The recovery rates to the nominal concentration were 3% and 6% for samples in 0.001 M CaCl2 solution and 0.01 M NaCl solution, respectively and 9% and 24% for samples in demin. and 0.01 M CaCl2 solution, respectively (not shown in the tables). These results demonstrated that the highest amount of test item could be rinsed from test vessel walls in 0.01 M CaCl2 solution.

Compared to samples in 0.01 M CaCl2 solution, the test item control samples in 0.001 M CaCl2 solution showed a slightly better recovery rate but the recovery was still only approx. 50% after 24 h. Samples in NaCl or demin. showed higher stabilities (less precipitation) after 24 h. Therefore, additional adsorption experiments were conducted with these test media.

 

Test vessel adsorption has been evaluated in these preliminary experiments and was observed to be 9% for test item control samples in demin. As test vessel adsorption is higher in control samples than in test item replicates (due to absence of soil and the higher adsorption to soil than to the test vessel) and as the mass balance is 90% in test item replicates (see below), the test vessel adsorption is considered to be negligible and was not further taken into account in Tier 2 and Tier 3.

 

Adsorption Experiments using 0.01 M NaCl and Demin:

Additional adsorption experiments were performed with 0.01 M NaCl solution and demin. as test medium. Test item control samples were observed to be stable in demin. for a duration of the experiment of 29 h , whereas the recovery rate of samples in 0.01 M NaCl was lower.

 

Tier 1:Adsorption Experiments LUFA 2.2 – 0.01 M NaCl + Demin.
soil / solution ratio: 1:100, applied test item concentration: 7000 µg/L, n=2

Matrix

 

Sampling point

 

[h]

Adsorption

 

[%]

Recovery rate test item control [%]

demin.

0

-

123

4

90

-

24

96

70

281)/ 292)

84

128

0.01 M NaCl

0

-

135

4

90

-

24

95

51

-                 not determined

1)               adsorption sample

2)               test item control sample

 

With regard to these results and the higher stability of the test item control sample, demineralized water was used as test medium for Tier 2 and Tier 3.

 

 

 

Mass Balance:

The soil extraction efficiency was evaluated with LUFA 2.2 and 2.4 soils using a soil solution ratio of 1:40. This ratio was chosen for the determination of the soil extraction efficiency for practical reasons.

Smaller centrifuge tubes could be used at this soil solution ratio which facilitated the transfer of the soil pellet after centrifugation.

The test item was extractable from soil using accelerated solvent extraction (ASE). Based on the observed total substance recovery (mass balance) of 90% it is considered justified to use the indirect method as basis for the calculation of the equilibrium adsorption constants.

 

Tier 1:Mass Balance
soil / solution ratio 1:40, applied test item concentration: 7000 µg/L, n=2

Matrix

Sampling point
[h]

Recovery rate from aqueous phase
[%]

Recovery rate from solid phase
[%]

Mass balance1)

[%]

LUFA 2.2

24

9

81

90

LUFA 2.4

24

6

84

90

1)          Sum of aqueous and solid phase

Tier 2–Adsorption Kinetics:

The adsorption kinetics was evaluated using a nominal test item concentration of 7.00 mg/L. A soil / solution ratio of 1:100 was used for each soil. After spiking, samples of the aqueous phase were measured at defined sampling points. In addition, test item control samples were analysed at each sampling point. The following table shows the amount of test item measured in the aqueous phase and based on this value the calculated amount adsorbed to the solid matrix (indirect method). The percentage of adsorption and recovery rate for the test item control are given after 24 h (adsorption equilibrium) and this sampling was used to calculate the distribution coefficients Kd and the corresponding organic carbon normalized distribution coefficients KOC.


 Measured Amounts in Aqueous Phase, Calculated Amount for Solid Matrices, Percent of Adsorption and Distribution Coefficients Kd and KOC

Applied test item concentration: 7000 µg/L, n = 2
equilibration time: 24 h

Soil type

msoil

[g]

Vaq

[mL]

madsaq(eq)


[µg]

madss(eq)


[µg]

Kd


[mL/g]

KOC


[mL/g]

Adsorption


[%]

Recovery Control [%]1)

LUFA 2.2

0.928

100

29.0

252

937

63732

90

90

LUFA 2.4

0.929

100

16.6

265

1720

98867

94

90

LUFA 5M

0.932

100

101

180

190

20765

64

86

Eurosoil 3

0.977

100

27.6

254

942

31279

90

81

Eurosoil 4

0.969

100

10.5

271

2667

203597

96

79

msoil          = used amount of soil (dry weight)

Vaq            = used volume of aqueous phase

madsaq        = amount of a.i. in the aqueous phase at equilibrium

madss          = amount of a.i. in the soil at equilibrium

1)              = recovery from initially measured (0 h) concentration after 24 h

Tier 3– Desorption Kinetics:

The desorption kinetics of the test item was evaluated during 24 h, using the soils of the adsorption kinetics test (after 24 h adsorption).The table below shows the 24 h desorption coefficient Kdes. Since the desorption coefficient is for certain soils higher than the adsorption coefficient Kd, the test item adsorption is considered to be not completely reversible.

Percent of Desorption and Desorption Coefficient Kdes 

Applied test item concentration: 7000 µg/L, n = 2

Soil Type

msoil[g]

Vaq[mL]

mdesaq(eq) [µg]

madss(eq) [µg]

Kdes[mL/g]

Desorption [%]

LUFA 2.2

0.928

100

12.4

252

2087

5

LUFA 2.4

0.929

100

15.1

265

1785

6

LUFA 5M

0.932

100

42.8

180

344

24

Eurosoil 3

0.977

100

14.8

254

1647

6

Eurosoil 4

0.969

100

12.5

271

2132

5

msoil          = used amount of soil (dry weight)

Vaq            = used volume of aqueous phase

mdesaq        = amount a.i. measured in the aqueous phase after desorption step

(without entrained water)

madss          = amount of a.i. adsorbed to soil at equilibrium

Tier 3– Adsorption Isotherms:

The adsorption isotherm was determined with additional concentrations of 3.00 mg/L, 16.5 mg/L, 23.5 mg/L and 30.0 mg/L after adsorption for 24 h. Deviating from the guideline, no concentration range in the order of two magnitudes was feasible. With regard to the limit of quantification, relatively high test item concentrations were required and applied to approx.1 g soil dry weight. The non-linearity of the adsorption is already observed at the concentration range used. This is demonstrated by the 1/n values (especially for LUFA 5M with 1/n = 0.69).

The table below shows the Freundlich adsorption coefficient Kd and the organic carbon normalized Freundlich adsorption coefficient KOCF.

 

Freundlich AdsorptionIsotherms

Applied test item concentrations: 3500, 7000, 16500, 23500, 30000 µg/L

Soil Type

msoil[g]

Vaq[mL]

r2

1/n

KadsF

KOCF

LUFA 2.2

0.928

100

0.993

0.94

833

56689

LUFA 2.4

0.929

100

0.946

0.91

1196

68742

LUFA 5M

0.932

100

0.955

0.69

178

19464

Eurosoil 3

0.977

100

0.969

0.85

630

20925

Eurosoil 4

0.969

100

0.926

0.93

1973

150645

msoil    = used amount of soil (dry weight) [g]

Vaq      = used volume of aqueous phase

n         = regression constant

%OC   = percentage of organic carbon content in the soil

KadsF    = Freundlich adsorption coefficient [µg1-1/n(mL)1/ng-1]

KOCF     = Freundlich adsorption coefficient normalized to content of organic carbon [µg1-1/n(mL)1/ng-1]

Tier 3– Desorption Isotherms:

The desorption isotherm was determined after adsorption for 24 h and desorption for 24 h. The non-linearity of the desorption is observed at the concentration range used.The table below summarizes the Freundlich desorption isotherm characteristics.

 

Freundlich Desorption Isotherms

Applied test item concentrations: 3500, 7000, 16500, 23500, 30000 µg/L

Soil Type

msoil[g]

r2

1/n

KdesF

LUFA 2.2

0.928

0.953

1.42

5148

LUFA 2.4

0.929

0.974

1.24

3508

LUFA 5M

0.932

0.983

0.62

232

Eurosoil 3

0.977

0.960

0.91

1289

Eurosoil 4

0.969

0.950

1.22

3312

msoil=      used amount of soil (dry weight) [g]

n      =      regression constant

KdesF =      Freundlich desorption coefficient [µg1-1/n(mL)1/ng-1]

Control Samples:

The test item stability was confirmed by measurement of two test item control replicates during each adsorption experiment. The table below shows the recovery rate for control samples. The recovery is related to the initially measured concentration at 0 h (recovery rates for samples at 0 h are related to the nominal applied concentration). The test item is considered to be stable in the test system, if demineralized water is used as test medium.

 

Recovery Rates [%] of the Control Samples

ConcentrationTier 2– Adsorption kinetics:7000 µg/L

ConcentrationTier 3– Adsorption isotherm: 3500 µg/L

 

LUFA 2.2

LUFA 2.4

LUFA 5M

Eurosoil 3

Eurosoil 4

Tier 2- adsorption kinetics 0 h

83

96

96

110

102

Tier 2- adsorption kinetics 2 h

93

84

93

461)

481)

Tier 2- adsorption kinetics 4 h

94

96

91

92

89

Tier 2- adsorption kinetics 6 h

79

103

81

90

84

Tier 2- adsorption kinetics 24 h

90

90

86

81

79

Tier 3- adsorption isotherm 0 h

97

95

92

95

81

Tier 3- adsorption isotherm 24 h

90

89

101

83

114

1)    = value not plausible, presumably related to sampling error

 

Validity criteria fulfilled:
yes
Conclusions:
Valid Guideline study performed under GLP conditions
Executive summary:

The adsorption / desorption behavior of the test item Sodiumoleylamphopolycarboxyglycinate (batch no.1297986) was investigatedin five different soils accordingto OECD guideline 106 and EC C.18 from 2017-02-20 to 2017-05-15 at Noack Laboratorien GmbH, 31157 Sarstedt, Germany. Distribution coefficients Kd and organic carbon normalized distribution coefficients KOC were determined with a single concentration. The desorption behavior / reversibility of the adsorption from the soils and the degree of adsorption and desorption as a function of the test item loading level (Freundlich adsorption and desorption isotherms) in the aqueous phase were investigated.

 

Experiments have been conducted in LUFA soils 2.2 and 2.4 using a soil / solution ratio of 1:100 during Tier 1. The solubility is high in demineralized water (demin.) but when CaCl2 0.01 M was used, precipitation occurred. The lower solubility in CaCl2 solution (soil-conditioned and un-conditioned) is presumably attributed to the calcium binding to the chelating part of the molecule. Since the test item concentration could not be lowered because of the relatively high limit of quantification, solubility / stability was also proven in 0.001 M CaCl2 solution, 0.01 M NaCl solution and demineralized water. With regard to the results of these experiments and the stability of the test item control samples (samples in soil-conditioned test medium without soil, spiked with the test item), demineralized water was used as test medium for Tier 2 and Tier 3. The mass balance was 90% in LUFA 2.2 and LUFA 2.4 and therefore the indirect method is considered acceptable for deriving the equilibrium constants throughout the study.

Experiments for adsorption and desorption kinetics were conducted with a soil / solution ratio of 1:100 and a nominal test item concentration of 7.00 mg/L. The adsorption equilibrium was reached after 24 hours. For investigations concerning the Freundlich adsorption and desorption isotherms, additional concentrations of 3.00 mg/L, 16.5 mg/L, 23.5 mg/L and 30.0 mg/L have been applied. The test substance concentrations used, did not cover a concentrationrange in the order of two magnitudes. With regard to the limit of quantification, relatively high test item concentrations were required with a soil solution ratio of 1 g soil to 100 mL of aqueous phase. The non-linearity of the adsorption is already observed at the concentration range used.

The table presents the observed distribution coefficients Kd and their corresponding organic carbon normalized distribution coefficients KOC. Furthermore, the mobility of the test item in the investigated matrices was classified according to McCallet al.(1980). Additionally, the desorption coefficient Kdes, the organic carbon normalized Freundlich adsorption coefficient KOCF as well asthe Freundlich desorption coefficient KdesF are presented in the summarizing table.


Summarized Endpoints

Mobility according to Mc Call et al.(1980): KOC 0 – 50 very high, KOC 50 – 150 high, KOC 150 – 500 medium, KOC 500 – 2000 low, KOC 2000 – 5000 slight, KOC > 5000 immobile; based on results of Tier 2
Kd and Koc were determined during Tier 2

Kdes, KOCF and KdesF were determined duringTier 3

 

ca.i.1)
[µg/L]

Kd[mL/g]

KOC[mL/g]

Kdes [mL/g]

KOCF
 
[µg1-1/n(mL)1/ng-1]

1/n

KdesF
 
[µg1-1/n(mL)1/ng-1]

Mobility according to McCallet al.

Soil type

Soil /solution ratio 1:100

LUFA 2.2

290

937

63732

2087

56689

0.94

5148

immobile

LUFA 2.4

166

1720

98867

1785

68742

0.91

3508

immobile

LUFA 5M

1015

190

20765

344

19464

0.69

232

immobile

Eurosoil 3

276

942

31279

1647

20925

0.85

1289

immobile

Eurosoil 4

261

2667

203597

2132

150645

0.93

3312

immobile

1)    = concentration of the active ingredient in the aqueous phase at equilibrium (Tier 2)

n    = regression constant (Freundlich adsorption isotherm)

 

The test item adsorbs strongly to all tested soils with Koc values > 5000. The desorption was determined to be not completely reversible. The adsorption does not show a linear correlation to the applied concentration (Freundlich adsorption isotherm). The 1/n values obtained from the isotherms demonstrate the non-linearity.

Description of key information

The adsorption / desorption behavior of Sodium oleylamphopolycarboxyglycinate was investigated in five different soils according to OECD guideline 106.

Freundlich adsorption and desorption isotherms using 5 different test concentrations were determined for each of the 5 soils. In addition distribution coefficients Kd and organic carbon normalized distribution coefficients KOC were determined at 7 mg/L. The mean Koc of Sodium oleylamphopolycarboxyglycinate for the 5 soils is 83648 L/kg

Key value for chemical safety assessment

Koc at 20 °C:
83 648

Additional information

The adsorption / desorption behavior of Sodiumoleylamphopolycarboxyglycinate was investigated in five different soils according to OECD guideline 106.

Freundlich adsorption and desorption isotherms using 5 different test concentrations were determined for each of the 5 soils. In addition distribution coefficients Kd and organic carbon normalized distribution coefficients KOC were determined with a single concentration.

 

During Tier 1 the soil solution ratio, the equilibration time, sorption to the test vessel and test substance stability were evaluated using LUFA soils 2.2 and 2.4. The solubility of the test item is high in demineralized water (demin.) but when CaCl20.01 M was used, precipitation occurred. The lower solubility in CaCl2 solution (soil-conditioned and un-conditioned) is presumably attributed to the calcium binding to the chelating part of the molecule. In relation to the detection limit and limited solubility of the test item in test media the test concentration in Tier 1 and 2 was 7 mg/L. Solubility and stability of the test item was shown in 0.001 M CaCl2solution, 0.01 M NaCl solution and demineralized water. The Tier 1 results showed that equilibrium was reached with 24 hours, that a soil solution ratio of 1:100 is needed and that there is a mass balance of 90% in LUFA 2.2 and LUFA 2.4 and that therefore the indirect method (back calculation of the concentration sorbed based on the observed concentration in the aqueous phase assuming 100% mass balance) is considered acceptable for deriving the equilibrium constants throughout the study.

In Tier 2 the adsorption coefficients Kd and Koc were determined for each of the 5 soils.

For Tier 3, measurement of the Freundlich adsorption and desorption isotherms, additional concentrations of 3.00 mg/L, 16.5 mg/L, 23.5 mg/L and 30.0 mg/L were introduced. The test substance concentrations used, did not cover a concentrationrange in the order of two magnitudes. With regard to the limit of quantification, relatively high test item concentrations were required with a soil solution ratio of 1 g soil to 100 mL of aqueous phase. The non-linearity of the adsorption is already observed at the concentration range used.

Kd and Koc for 5 soils were determined during Tier 2 at 7 mg/L

Kdes,KOCF and KdesF were determined duringTier 3

 

ca.i.1)
[µg/L]

Kd[mL/g]

KOC[mL/g]

Kdes [mL/g]

KOCF
 
[µg1-1/n(mL)1/ng-1]

1/n

KdesF
 
[µg1-1/n(mL)1/ng-1]

Mobility according to McCallet al.

Soil type

Soil /solution ratio 1:100

LUFA 2.2

290

937

63732

2087

56689

0.94

5148

immobile

LUFA 2.4

166

1720

98867

1785

68742

0.91

3508

immobile

LUFA 5M

1015

190

20765

344

19464

0.69

232

immobile

Eurosoil 3

276

942

31279

1647

20925

0.85

1289

immobile

Eurosoil 4

261

2667

203597

2132

150645

0.93

3312

immobile

1)    = concentration of the active ingredient in the aqueous phase at equilibrium (Tier 2)

n    = regression constant (Freundlich adsorption isotherm)

 

The test item adsorbs strongly to all tested soils withKocvalues > 5000. The desorption was determined to be not completely reversible. The adsorption does not show a linear correlation to the applied concentration (Freundlich adsorption isotherm). The 1/n values obtained from the isotherms demonstrate the non-linearity.