Glycine, N,N'-1,2-ethanediylbis-, reaction products with formaldehyde, iron chloride (FeCl3) and phenol, potassium salts

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:

2020-02-10 to 2020-03-13

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

The number of soils which were used deviates from the recommendation in the guideline as three soils were used instead of the recommended five soils. The Freundlich isotherm was not determined and the adsorption behavior was investigated based on two different test item concentrations. The desorption behavior was investigated.

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

Details are given below under "Principles of method if other than guideline"

Qualifier:

according to guideline

Guideline:

other: Council Regulation (EC) No. 440/2008, Method C.18 (2008)

Deviations:

no

Principles of method if other than guideline:

The number of soils which were used deviates from the test guideline recommendation in the guideline as three soils were used instead of the recommended five soils. Considering the low expected sorption, the Freundlich isotherm was not determined and the adsorption behavior was investigated based on two different test item concentrations. The desorption behavior was investigated.

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: HBED-Fe

CAS-No: 1463474-95-4

Batch number: FC-C 11140

Active substance: Reaction product of phenol, formaldehyde, ethylenediamine diacetic acid, iron chloride and metal hydroxide

Purity: 96.6% (UVCB)

Appearance: Dark red-brown microgranules (solid)

Stability under test: Stable
conditions

Expiry date: 2022-08-31

Recommended storage: Keep in a dry place. Store at room temperature in the original container. Keep container tightly closed.

Radiolabelling:

no

Test temperature:

Nominal: 20 - 25 °C

Analytical monitoring:

yes

Details on sampling:

Test Procedure

The study was performed in accordance to OECD-Guideline for Testing of Chemicals No. 106 (2000) and Council Regulation (EC) No. 440/2008, C.18 (2008).

Test vessels
50 mL and 225 mL polypropylene centrifugation tubes

Concentration for adsorption experiments
K1: 0.5 mg/L
K2: 5.0 mg/L

Stock solutions
A stock solution of 1000 mg/L of HBED-Fe in ultrapure water was prepared.

Preparation of the soil samples (conditioning)
The soils were weighed into the test vessels and an appropriate volume of 0.01 M CaCl2-solution 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. Max 0.5 volume-% of the stock solutions, related to the volume experiments of the aqueous phase in the soil suspensions were added in order to obtain the intended test concentrations. Afterwards, the samples were agitated.

Preparation of the samples for desorption experiments
Samples at adsorption equilibrium were used for this purpose. The test vessels were centrifuged after completion of the adsorption experiments, weighed to quantify the amount of entrained water in the solid phase and the supernatant was replaced by fresh 0.01 M CaCl2-solution. Then, the test vessels were agitated again to investigate the desorption behaviour of the test item at one sampling point (24 hours).

Samples for analysis
The soil suspensions were centrifuged after agitation at 4000 rpm to separate the phases, followed by analysing the concentration of the test item in aqueous phase by LC-MS/MS. Test vessel adsorption was determined in test item control samples. For analysis of the soil, the aqueous phase was decanted and the soil was extracted. Extracts were also analysed by LC-MS/MS.

Replicates
Duplicates

CONTROLS
CaCl2-solution was conditioned as described above, followed by separation of the aqueous phase by centrifugation at 4000 rpm . Then the aqueous phase was fortified acc. to the concentrations used for the test item samples of K1 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.

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

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

Sample Preparation

Dilution medium (DM A) 0.01 M CaCl2 solution conditioned with the respective soil (1:1) containing 10 mmol TbAOH and 2% formic acid

Dilution medium (DM) 0.01 M CaCl2 solution conditioned with the respective soil (1:1) containing 5 mmol TbAOH and 1% formic acid

Standards
A stock solution of 1000 mg test item/L in ultrapure water was prepared. The solution was diluted to 7 calibration standards in the range of 10 to 200 µg test item/L with DM.

Aqueous phase
After centrifugation with 4000 rpm for 5 min, an aliquot of each aqueous sample was stabilized by dilution with DM A (factor 2) and analysed. The samples were further diluted with DM. The samples were stored in the dark until analysis.

Soil extraction
The wet soil was used for extraction after decantation of the aqueous phase. The soil was extracted at room temperature. 3 mL methanol : ultrapure water (50 : 50 v/v) were added to the wet soil. The vessel was shaken for 45 min. The suspensions were centrifuged at 4000 rpm for 5 min. The extraction was repeated twice. The samples were stored in the dark during extraction and until analysis. The extracts were transferred quantitatively into a 10 mL measuring flask and filled up with methanol : water (50 : 50 v/v). For analysis the samples had to be filtered and diluted. The first dilution step was factor 2 with DM A. The samples were further diluted with DM, if necessary.

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 other: mval/100 g

Matrix no.:

#2

Matrix type:

other: silty sand

% Clay:

8.6

% Silt:

29.3

% Sand:

62.1

% Org. carbon:

0.412

pH:

5.9

CEC:

4.9 other: mval/100 g

Matrix no.:

#3

Matrix type:

clay loam

% Clay:

23.3

% Silt:

38.6

% Sand:

38.1

% Org. carbon:

1.85

pH:

7.4

CEC:

22 other: mval/100 g

Details on matrix:

Reason for the selection
These matrices are suitable for the conduction of the study because all parameters with impact on the adsorption / desorption behavior of a chemical substance were considered.

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

Storage at test facility
Room temperature, in closed containers

Details on test conditions:

CaCl2-solution:
Ultrapure water was used to prepare the CaCl2-solution (0.01 M).

Soil / Solution ratio
1:2 (only Lufa 2.2), 1:1

Sampling points
0h, 5h, 24h, 29h and 48h

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

Test temperature
The temperature was mainly in the range of 20 to 21 °C during the course of the study. The temperature dropped occasionally down to 19 °C.

Key result

Sample No.:

#1

Type:

Kd

Value:

0.3 L/kg

Temp.:

20 °C

Matrix:

LUFA 2.2 soil/solution ratio 1:1 0.5 mg/L

% Org. carbon:

1.47

Key result

Sample No.:

#1

Type:

Koc

Value:

20 L/kg

Temp.:

20 °C

Matrix:

LUFA 2.2 soil/solution ratio 1:1 0.5 mg/L

% Org. carbon:

1.47

Key result

Sample No.:

#2

Type:

Kd

Value:

0.076 L/kg

Temp.:

20 °C

Matrix:

LUFA 2.3 soil/solution ratio 1:1 0.5 mg/L

% Org. carbon:

0.412

Key result

Sample No.:

#2

Type:

Koc

Value:

18 L/kg

Temp.:

20 °C

Matrix:

LUFA 2.3 soil/solution ratio 1:1 0.5 mg/L

% Org. carbon:

0.412

Key result

Sample No.:

#3

Type:

Kd

Value:

0.26 L/kg

Temp.:

20 °C

Matrix:

LUFA 2.4 soil/solution ratio 1:1 0.5 mg/L

% Org. carbon:

1.85

Key result

Sample No.:

#3

Type:

Koc

Value:

14 L/kg

Temp.:

20 °C

Matrix:

LUFA 2.4 soil/solution ratio 1:1 0.5 mg/L

% Org. carbon:

1.85

Key result

Sample No.:

#1

Type:

Kd

Value:

0.2 L/kg

pH:

6.8

Temp.:

20 °C

Matrix:

LUFA 2.2 soil/solution ratio 1:1 5 mg/L

% Org. carbon:

1.47

Key result

Sample No.:

#1

Type:

Koc

Value:

14 L/kg

pH:

6.8

Temp.:

20 °C

Matrix:

LUFA 2.2 soil/solution ratio 1:1 5 mg/L

% Org. carbon:

1.47

Key result

Sample No.:

#2

Type:

Kd

Value:

0.067 L/kg

pH:

7.2

Temp.:

20 °C

Matrix:

LUFA 2.3 soil/solution ratio 1:1 5 mg/L

% Org. carbon:

0.412

Key result

Sample No.:

#2

Type:

Koc

Value:

16 L/kg

pH:

7.2

Temp.:

20 °C

Matrix:

LUFA 2.3 soil/solution ratio 1:1 5 mg/L

% Org. carbon:

0.412

Remarks on result:

other: The Koc is included only for comparison reasons. HBED is anionic and sorption data should therefore not be normalized to the organic carbon content

Key result

Sample No.:

#3

Type:

Kd

Value:

0.19 L/kg

pH:

7.5

Temp.:

20 °C

Matrix:

LUFA 2.4 soil/solution ratio 1:1 5 mg/L

% Org. carbon:

1.85

Key result

Sample No.:

#3

Type:

Koc

Value:

10 L/kg

pH:

7.5

Temp.:

20 °C

Matrix:

LUFA 2.4 soil/solution ratio 1:1 5 mg/L

% Org. carbon:

1.85

Results

 

The following table gives an overview on the obtained results of the study.

 

Overview on the Results

Parameter	Result
Determination of soil / solution ratios with the aim to obtain at least an adsorption of > 20%	Adsorption partly below 20%
Time to reach adsorption equilibrium	48 h for LUFA 2.2 and LUFA 2.3; 24 h for LUFA 2.4
Adsorption to the test vessel	No adsorption observed
Investigation of stability (parental massbalance)	Substance was stable
Desorption behavior	low (as adsorption is very low)

Adsorption and Stability in the Test System

Lufa 2.2 soil was used for the first experiment for preliminary investigations on the adsorption behavior of the test item with a soil / solution ratio of 1:2 at both concentrations (K₁ and K₂). Samples of the aqueous phase were taken after 0h, 5h, 24h, 29h and 48h agitation. Because of the low adsorption (see table below), further experiments were conducted with a soil / solution ratio of 1:1.

 

 

Adsorption Experiments Lufa 2.2, soil / solution ratio of 1:2

n = 2

Applied concentration, test item [mg/L]^1)	Sampling point [h]	Adsorption indirect [%]
0.478	0	13
	5	13
	24	15
	29	14
	48	15
4.78	0	6
	5	6
	24	7
	29	7
	48	7

1) = purity of the test item and weighing factor taken into account

 

Lufa 2.2, Lufa 2.3 and Lufa 2.4 with a soil / solution ratio of 1:1 at both concentrations (K₁ and K₂) were used for further investigations on the adsorption behavior of the test item. With regard to the amount of overlaying aqueous phase and to avoid sedimentation, 1:1 is the highest technically feasible soil / solution ratio for the used soils. Although this ratio was used, the adsorption was very low. The adsorption equilibrium was reached for all soils after 24 h. The following tables show the results, the adsorption is calculated based on measured concentrations in the aqueous phase.

 

Adsorption Experiments Lufa 2.2, soil / solution ratio of 1:1

n = 2

Applied concentration, test item [mg/L]^1)	Sampling point [h]	Adsorption indirect [%]
0.478	0	3
	5	0
	24	12
	29	7
	48	4
4.78	0	10
	5	16
	24	13
	29	12
	48	15

                         

1) = purity of the test item and weighing factor taken into account

 

Adsorption Experiments Lufa 2.3, soil / solution ratio of 1:1

n = 2

Applied concentration, test item [mg/L]^1)	Sampling point [h]	Adsorption indirect [%]
0.478	0	-2
	5	3
	24	2
	29	-1
	48	12
4.78	0	-2
	5	0
	24	2
	29	2
	48	19

                         1) = purity of the test item and weighing factor taken into account

 

Adsorption Experiments Lufa 2.4, soil / solution ratio of 1:1

n = 2

Applied concentration, test item [mg/L]^1)	Sampling point [h]	Adsorption indirect [%]
0.478	0	15
	5	21
	24	13
	29	13
	48	38
4.78	0	10
	5	22
	24	4
	29	-2
	48	31

                         1) = purity of the test item and weighing factor taken into account

 

The distribution coefficients K_d (indirect) ranged from 0.067 mL/g to 0.30 mL/g and the corresponding organic carbon normalized distribution coefficients K_OC from 10 mL/g to 20 mL/g. Results for K_d and K_OC are given in the table below for the indirect method, calculated from measured concentrations in the aqueous phase, for all tested soils and concentrations. As K_d is below 0.3 mL/g, the endpoints were also calculated from measured concentrations in aqueous and solid phase (direct method). Regarding K₂ in LUFA 2.3 and LUFA 2.4, ‘negative adsorption’ was calculated, since amounts of test item measured after soil extraction were very low and lower than the calculated remaining amount of test item in the pore water. Therefore, results obtained by using the indirect method should be considered to evaluate the adsorption behavior.

 

Endpoints forHBED-Fe

 

	indirect method		direct method
	Kd [mL/g]	KOC [mL/g]	Kd [mL/g]	KOC [mL/g]
K1 = 0.5 mg/L
LUFA 2.2	0.30	20	0.29	20
LUFA 2.3	00.076	18	0.14	33
LUFA 2.4	0.26	14	0.17	09
K2 = 5 mg/L
LUFA 2.2	0.20	14	0.014	1
LUFA 2.3	00.067	16	-^1)	-^1)
LUFA 2.4	0.19	10	-^1)	-^1)

1) not applicable

 

During experiments, test item control samples (the test item dissolved in the respective soil-conditioned 0.01 M CaCl₂) showed that the test item is stable in the aqueous phase and after 48h there was no indication of adsorption to the test vessel. As the recovery rate was below 90% for LUFA soil 2.4, the adsorption and the mass balance were determined after 24 h.

 

 

Test Item Control Samples

applied test item concentration¹⁾: 0.478 mg/L, n = 2

Soil	Soil : Solution Ratio	Sampling point [h]	Recovery [%]
Lufa 2.2	1:2	0	92
		48	99
	1:1	0	99
		48	100
Lufa 2.3	1:1	0	101
		48	97
Lufa 2.4	1:1	0	100
		48	84
		0	93
		24	104

1)    = purity of the test item and weighing factor taken into account

 

 Extraction from Soil / fresh Spikes

Various solvents have been tested (non-GLP) on freshly spiked Lufa 2.2 soil with a soil / solution ratio of 1:2. The best results were obtained with methanol / ultrapure water 50 / 50 without containing any chemical additives. Loss due to sorption to the filter was tested by filtering of one calibration standard (recovery rate 92%: acceptable). A blank soil extract was spiked with different concentrations of test item and diluted with the respective extraction medium at different ratios to evaluate if the impact of the co-extracted matrix components on the chemical analysis could be reduced. A summary of the tested extraction methods used is given in the following table.

 

Method Development Soil Extraction – Fresh Spikes

Lufa 2.2, soil / solution ratio 1:2, n = 2

 

Extraction method	Filtration needed	Applied test item	Dilution factor for analysis	Recovery rate [%]
Methanol / ultrapure water 50 / 50 containing 5 mmol TbAOH and 1% formic acid 3 x 30 mL	No	47.8 µg	10	81
Methanol / ultrapure water 50 / 50 3 x 30 mL	Yes	47.8 µg	10	101
Methanol 3 x 30 mL	No	47.8 µg	10	45
Methanol / ultrapure water 50 / 50 3 x 30 mL	Yes	47.8 µg/L	1	58
		95.6 µg/L	2	79
		239 µg/L	5	95
		478 µg/L	10	112
Methanol / ultrapure water 50 / 50 3 x 3 mL	Yes	4.78 µg	5	95

 

Mass Balance

 

Experiments concerning the mass balance were conducted with Lufa 2.2, Lufa 2.3 and Lufa 2.4 soils with both concentrations (K₁ and K₂). The resulting recoveries obtained are shown in the tables below. The test item is stable in the tested time range.

 

Adsorption and Mass Balance – Lufa 2.2

Soil / solution ratio: 1:1, n = 2

Applied concentration, test item [mg/L]^1)	Sampling Point [h]	Recovery Aqueous Phase [%]	Adsorption indirect [%]^1)	Recovery Soil [%]	Mass Balance [%]
0.478	48	78	22	21	100
4.78		84	16	1	85

1) = purity of the test item and weighing factor taken into account, adsorption calculated from determined concentrations in the aqueous phase (indirect method)

 

Adsorption and Mass Balance – Lufa 2.3

Soil / solution ratio: 1:1, n = 2

Applied concentration, test item [mg/L]^1)	Sampling Point [h]	Recovery Aqueous Phase [%]	Adsorption indirect [%]^1)	Recovery Soil [%]	Mass Balance [%]
0.478	48	93	7	12	105
4.78		94	6	-1	93

1) = purity of the test item and weighing factor taken into account, adsorption calculated from determined concentrations in the aqueous phase (indirect method)

 

Adsorption and Mass Balance – Lufa 2.4

Soil / solution ratio: 1:1, n = 2

Applied concentration, test item [mg/L]^1)	Sampling Point [h]	Recovery Aqueous Phase [%]	Adsorption indirect [%]^1)	Recovery Soil [%]	Mass Balance [%]
0.478	24	82	18	12	94
4.78		85	15	0	85

1) = purity of the test item and weighing factor taken into account, adsorption calculated from determined concentrations in the aqueous phase (indirect method)

 

 

Desorption

The desorption behavior of the test item was determined after 48 h adsorption. Details are shown in the table below. The test item shows very low adsorption to soils and consequently will have a high mobility. For LUFA 2.2 and LUFA 2.3 K₁, no desorption was observed. For LUFA 2.3 and LUFA 2.4, K_des was in the range of 4.8 mL/g to 11 mL/g.

A low fraction of the test item adsorbed to soil and only low amounts of the test item were measured in the desorption experiments. Therefore, high standard deviation was observed in the desorption experiments.

 

 

Desorption Experiments

Applied concentration, test item¹⁾:        K₁ = 0.478 mg/L, K₂ = 4.78 mg/L

Applied amount, test item¹⁾:                   K₁ = 4.78 µg, K₂ = 47.8 µg

time to reach equilibrium                      48 h

soil / solution ratio                                    1:1

n = 2; V_aq= 10 mL

Soil Type	Conc.	Rep	msoil [g]	m^desaq(eq) [µg]	m^adss(eq) [µg]	Desorption [%]	Kdes [mL/g]
LUFA 2.2	K1	I	9.28	< LCL	00.320	-	-
		II			00.443
	K2	I			9.37
		II			7.02
LUFA 2.3	K1	I	9.61	-0.0644	00.142	-	-
		II		-0.0257	00.208
	K2	I		-1.40	02.33	-	7.9
		II		2.58	7.82	33
LUFA 2.4	K1	I	8.87	0.254	1.52	17	4.8
		II		0.343	1.60	21
	K2	I		1.51	13.7	11	11
		II		0.857	12.7	7

1)        = purity of the test item and weighing factor taken into account

Conc. = concentration, see above

Rep     = replicate number

-          = could not be calculated, due to low measured concentrations

Validity criteria fulfilled:

yes

Conclusions:

The test material is concluded to have high mobility in soils.

Executive summary:

Summary

General Information

The adsorption / desorption behavior of the test item HBED-Fe (batch no.FC-C11140) was investigated in three different soils in a refined study setup according to OECD guideline 106 and Council Regulation (EC) No. 440/2008, C.18 from 2020-02-10 to 2020-03-13 at Noack Laboratorien GmbH, 31157 Sarstedt, Germany. Relevant properties of the used soils are given in the table below. Distribution coefficients K_d and organic carbon normalized distribution coefficients K_OC were determined with two concentrations. Furthermore, investigations about the desorption behavior were performed. The test item was analysed by LC-MS/MS and the analytical method was validated for the aqueous phase.

 

Relevant Characteristics of Test Matrices

	Soils
	LUFA 2.2	LUFA 2.3	LUFA 2.4
batch	F2.2 4016	F2.3 4116	F2.4 2617
Soil Type^1)	Loamy sand	Silty sand	Clayey loam
pH (0.01 M CaCl2)^3)	5.4	5.9	7.4
Organic Carbon [%]^2)	1.47	0.412	1.85
Clay (<0.002 mm) [%]^2)	8.5	8.6	23.3
Silt (0.002-0.063 mm) [%]^2)	11.3	29.3	38.6
Sand (0.063-2 mm) [%]^2)	80.2	62.1	38.1
Cation Exchange Capacity [mval/100g]^2)	7.6	4.9	22

1)according to German DIN

2)determined at Agrolab Agrar und Umwelt GmbH (non-GLP)

3) Analyses data sheet provided by LUFA

 

Results

Experiments for adsorption kinetics and desorption were conducted with nominal test item concentrations of 0.5 mg test item/L (K₁) and 5 mg test item/L (K₂). Though the highest feasible soil / solution ratio of 1:1 was used, only low adsorption (from 4 to 38%) of the test item to soil was observed after 24 hours (only Lufa 2.4) and 48 hours (LUFA 2.2 and LUFA 2.3). The distribution coefficients K_d (indirect) ranged from 0.067 mL/g to 0.30 mL/g and the corresponding organic carbon normalized distribution coefficients K_OC from 10 mL/g to 20 mL/g. These results indicate that the test item has a very high mobility in all soils. Results for K_d and K_OC are given in the table below for the indirect method, calculated from measured concentrations in the aqueous phase, for all tested soils and concentrations. As K_d is below 0.3 mL/g, the endpoints were also calculated from measured concentrations in aqueous and solid phase (direct method). Regarding K₂ in LUFA 2.3 and LUFA 2.4,‘negative adsorption’ was calculated, since amounts of test item measured after soil extraction were very low and lower than the calculated amount of test item in the pore water. Therefore, results obtained by using the indirect method should be considered to evaluate the adsorption behavior.

 

 

 

Summarized Endpoints forHBED-Fe

Mobility according to McCall et al. (1980): K_OC 0 – 50 very high, K_OC 50 – 150 high, K_OC 150 – 500 medium, K_OC 500 – 2000 low, K_OC 2000 – 5000 slight, K_OC > 5000 immobile; calculations with the results of the indirect and direct method

	indirect method						direct method
	Kd[mL/g]	KOC[mL/g]	Mass Balance [%]		Mobility according to McCall et al.	Kdes[mL/g]	Kd[mL/g]	KOC[mL/g]	Mobility according to McCall et al.
K1= 0.5 mg/L
LUFA 2.2	0.30	20		100	very high	-^1)	0.29	20	very high
LUFA 2.3	00.076	18		105	very high	-^1)	0.14	33	very high
LUFA 2.4	0.26	14		94	very high	4.1	0.17	09	very high
K2= 5 mg/L
LUFA 2.2	0.20	14	85		very high	-^1)	0.014	1	very high
LUFA 2.3	00.067	16	93		very high	5.1	-^1)	-^1)	very high
LUFA 2.4	0.19	10	85		very high	9.9	-^1)	-^1)	very high

1) not applicable

 

During experiments, test item control samples (the test item dissolved in the respective soil-conditioned 0.01 M CaCl₂) showed that the test item is stable in the aqueous phase and no indication for adsorption to the test vessel takes place.

The parental mass balance for the test item was determined after an equilibration time of 24 hours (only Lufa 2.4) and 48 hours (LUFA 2.2 and LUFA 2.3) and was calculated by taking into account the test item recovery in the aqueous phase, the soil and residual test item in pore water. A mass balance in the range of 85 to 105% was determined.

 

The desorption behavior of the test item was determined after 48 h equilibration. The test item shows a very low adsorption to soils and a high mobility. For LUFA 2.2 and LUFA 2.3 K1, no desorption was observed. For LUFA 2.3 and LUFA 2.4,K_des was in the range of 4.1 mL/g to 11 mL/g. As K_des is higher than K_d, if desorption was determined, the adsorption is assumed to be not completely reversible.

A low fraction of the test item adsorbed to soil and thus only low amounts of the test item were measured in the desorption experiments. Therefore, high standard deviations were observed in the desorption experiments.

 

The determined low adsorption after 24 h and 48 h, respectively, using the highest technically feasible soil / solution ratio of 1:1 confirmed the refined study setup.

Description of key information

Based on different types of information (calculation, sorption study and stability in the presence of soil), it is concluded HBED-Fe has a low potential for adsorption and can be concluded to have high mobility in soil.

Key value for chemical safety assessment

Koc at 20 °C:

15.33

Other adsorption coefficients

Type:

log Kp (solids-water in soil)

Value in L/kg:

0.067

at the temperature of:

20 °C

Other adsorption coefficients

Type:

log Kp (solids-water in soil)

Value in L/kg:

0.3

at the temperature of:

20 °C

Additional information

Based on the calculated Koc value (Kow method, KocWIN, Zvinavashe 2013), it was already concluded that HBED-Fe has a low potential for adsorption, log Koc was estimated between -3.3 and - 4.6. This low predicted sorption potential was confirmed in a refined (3 soils instead of 5) OECD 106 study by Landsberg. In this study experiments for adsorption kinetics and desorption were conducted with nominal test item concentrations of 0.5 mg test item/L (K₁) and 5 mg test item/L (K₂).Though the highest feasible soil / solution ratio of 1:1 was used, only low adsorption (from 4 to 38%) of the test item to soil was observed after 24 hours (only Lufa 2.4) and 48 hours (LUFA 2.2 and LUFA 2.3). The distribution coefficients K_d (indirect) ranged from 0.067 mL/g to 0.30 mL/g and the corresponding organic carbon normalized distribution coefficients K_OC from 10 mL/g to 20 mL/g (mean 15.33 mL/g). These results indicate that the test item has a very high mobility in all soils.

A non-guideline sorption study confirmed the limited adsorption for the structurally related UVCB EDDHMA-Fe when considering Ca-montmorillonite, peat and ferrihydrite as soil materials (low distribution coefficients, Hernandez-Apaolaza & Lucena, 2001). In this study, the influence of concentration, pH and type of isomer was also studied and proved of relevance to the sorption behavior. Full understanding of the adsorption of metal chelates by soils will always be impeded by the complexity of soil surfaces, continuing changes in chelate speciation and concurrent degradation of the chelating ligand.

Additionally, a stability study in water solution at different pH's and in the presence of three different suspended soils showed the stability of EDDHMA-Fe by measurement of Fe concentrations in solution (Bar-Yosef, 1985).