Tetrasodium 4,4'-bis[[4-morpholino-6-(p-sulphonatoanilino)-1,3,5-triazin-2-yl]amino]stilbene-2,2'-disulphonate

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption

Remarks:

adsorption

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Principles of method if other than guideline:

Calculation using SRC PCKOCWIN v2.0

GLP compliance:

no

Type of method:

other: calculation using SRC PCKOCWIN v2.0

Media:

soil

Type:

log Koc

Value:

11.637 - 11.782

Remarks on result:

other: Estimated, MCI method.

Type:

log Koc

Value:

0.951 - 2.606

Remarks on result:

other: Estimated, Kow method.

Estimation based on the acid form

Koc: 1E+010 l/kg (MCI method)

Koc : 403.5 l/kg (Kow method)

Log Koc: 11.782 (MCI method)

Log Koc: 2.606 (Kow method)

Estimation based on the bound [Na] form

Koc: 1E+010 l/kg (MCI method)

Koc : 8.936 l/kg (Kow method)

Log Koc: 11.637 (MCI method)

Log Koc: 0.951(Kow method)

Conclusions:

MCI method:
log Koc: 11.637 - 11.782 (acid form - bound [Na] form, respectively)
Kow method:
log Koc: 0.951 - 2.606 (acid form - bound [Na] form, respectively)

Executive summary:

Method

The partition coefficient octanol/carbon was calculated using SRC PCKOCWIN v2.0. Kocwin is an application contained in the EpiSuite 4.1, the suite of physical/chemical property and environmental fate estimation programs developed by the EPA’s Office of Pollution Prevention Toxics and Syracuse Research Corporation (SRC).

Results

MCI method:

log Koc: 11.637 - 11.782 (acid form - bound [Na] form, respectively)

Kow method:

log Koc: 0.951 - 2.606 (acid form - bound [Na] form, respectively)

Reference 2

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Experiment start date - 15 March 1993; Experiment end date - 24 March 1993; Study completion date - 19 May 1993.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Read-across based on grouping of substances (category approach). A detailed category justification is included in chapter 13 of this dossier.

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted May 12, 1981

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Test temperature:

Room temperature

Analytical monitoring:

yes

Details on matrix:

SOIL TYPES
For the study three different soils differing in pH, clay content, organic matter content, and thus in cation exchange capacity were used:
Origin:
1. Soil l (Standard soil LUFA 2.1, sand)
2. Soil II (Standard soil LUFA 2.2, loamy sand)
3. Soil III (Standard soil LUFA 2.3, sandy loam)
- Source: Landwirtschaftliche Untersuchungs- und Forschungsanstalt (LUFA), D-6720 Speyer/F.RG.
- Storage: at room temperature until use.

Details on test conditions:

TEST SYSTEM
- Soil preparation: already conditioned, sieved soils (2.0 mm screen) were used for the experiment. Before experimental start the dry weight of the standard soils was determined. Therefore, subsamples of approximately 20 g of each soil type were dried for 16 hours at 110 °C.

STOCK SOLUTION
- Preparation: 10.9 mg of the test item were dissolved in 100 ml of deionised water to prepare a stock solutions of 109.0 µ/ml of the test compound.
- Diluted solutions: calculated volumes of this stock solutions were diluted with deionised water to obtain standard solutions in the range from 0.055 µg/ml to 10.9 µg/ml test item.

Type:

Koc

Value:

>= 2 840 - <= 10 000 L/kg

Matrix:

Sand

% Org. carbon:

0.7

Type:

log Koc

Value:

> 3.45 - <= 4 dimensionless

Matrix:

Sand

% Org. carbon:

1.34

Adsorption and desorption constants:

The obtained results show that the amounts of test item adsorbed by the chosen soils ranged from 85 % (LUFA 2.1, sand) to 98 % (LUFA 2.2 loamy sand). From these amounts less than 5 % of the total initially adsorbed amounts of test item were desorbed.

Recovery of test material:

Recoveries were performed to proof the analytical method during the study. Therefore, water control samples were fortified with test compound.
Screening Adsorption: 100.9-108.3 %
Screening Desorption: 90.9-100.9 %

Details on results (Batch equilibrium method):

BLANKS
No test item could be detected in the supernatants after blank tests with three soils, which were treated with 0.01 M CaCl2-solution without test article.

PRELIMINARY TEST
The obtained results show that the chosen chemical analysis is reproducible and satisfy.

SCREENING TEST
Adsorption
Recovery tests without soil were performed parallel to the screening adsorption test to eliminate the influence of the test system (e. g. centrifugation tubes) on the results of the tests performed in the presence of soil. Therefore, two duplicate blank tests were performed for a concentration of 4.91 mg/l.
A significant difference to the applied amount of the test compound was not found. Hence, a correction was not necessary.

Overview of results

	LUFA 2.3 sandy loam	LUFA 2.1 sand	LUFA 2.2 loamy sand
pH	6.6	5.9	5.8
max. water cap. (g/100 g TM)	35.3	26.1	44
Organic Carbon [%]	1.34	0.7	2.29
<0.02 mm [%]	19.6	7.9	10.1
Clay (<0.002 mm) [%]	8.3	3.5	5.1
Silt (0.002-0.063 mm)[%]	3.9	1.9	2.1
Sand (0.063-2 mm) [%]	88	94.6	92.9
Cation Exchange Capacity [mval/100g]	9.5	4.9	9.7
Total-N [%]	0.11	0.06	0.17
Koc [dm³/g]	2.84	4.21	10
Koc [ml/g]	2840	4210	10000
logkoc	3.4	3.6	4
% of asdorbed test item not desorbed	>96.1 >96.2	>95.4 >94.9	>96.2 >96.1

Results obtained for the validation of the analytical method.

Nominal concentration of the test item [mg/l]	Concentration of the test item found, calc. on basis of its peak area [mg/l]	Recovery [%]
0.11	0.117 0.100	106.5 88.5
0.55	0.535 0.536	97.0 97.5
1.09	1.107 1.061	101.5 97.0
Mean		98.0 ± 6.0 SD

Results obtained for the concentrations of test substance in the blanks of the screening adsorption test.

Soil	Concentration of test item found calculated on basis of its peak area [mg/l]
A (LUFA, 2.1)	n. d./n. d.*
B (LUFA, 2.2)	n. d./n. d.*
C (LUFA, 2.3)	n. d./n. d.*

*: not detectable

CALIBRATION CURVE

The lowest practical quantification limit found was 0.11 µg/ml of the test item. Water control samples (soil A, duplicate test) were fortified with test item. The spiking levels ranged from 0.11 µg/ml to 1.09 µg/ml. A mean recovery of 98 % with a standard deviation of ± 6.0 % was determined. Therefore the study is considered to be valid.

RECOVERIES DURING THE STUDY

Results obtained for the recovery of the test item during the study.

Test phase	Nominal concentration of the test item [mg/l]	Concentration of the test item found, calc. on basis of its peak area [mg/l]	Recovery [%]
Screening adsorption	2.18	2.2	100.9
		2.21	101.4
	4.36	4.72	108.3
		4.41	101.1
Screening desorption	0.11	0.1	90.9
		0.1	90.9
	2.18	2.18	100
		2.2	100.9
Mean			99.3 ± 5.8 SD

PRELIMINARY TEST

Soil	Nominal concentration of test item [mg/l]	Concentration of test item found calculated on basis of its peak area [mg/l]	Recovery [%]
A (LUFA, 2.1)	4.36	4.61 4.65	105.7 106.7
B (LUFA, 2.2)	4.36	4.58 4.60	105.0 105.5
C (LUFA, 2.3)	4.36	4.69 4.70	107.6 107.8
Mean			106.4 ±1.2 SD

SCREENING TEST

Results obtained for the recovery of test item without soil matrix of screening adsorption test.

Nominal concentration of test item [mg/l]	Concentration of test item found calculated on basis of its peak area [mg/l]	Recovery [%]
4.91	4.90 4.92	99.8 100.2

Distribution of the test item between soil and aqueous phase of various soils at room temperature.

Test item conc. In aqueous medium after correction [µg/ml]	A (LUFA, 2.1)		B (LUFA, 2.2)		C (LUFA, 2.3)
	Ce [µg/ml]	x/m [µg/g]	Ce [µg/ml]	x/m [µg/g]	Ce [µg/ml]	x/m [µg/g]
4.91	0.73	21.9	0.11	27.4	0.59	24.4
	0.76	22.0	0.13	27.4	0.68	23.6

Ce: concentration of the test article in aqueous phase [µg/ml]; x/m: amount of the test article adsorbed per unit mass [g] of adsorbent.

Freundlich adsorption constants and adsorption constants as a function of the organic carbon content of various soils treated.

Parameter	Unit	Soil
		A (LUFA, 2.1)	B (LUFA, 2.2)	C (LUFA, 2.3)
Amount of the test item absorbed	%	84.8	97.6	87.1
K	(ml/g)	29.5	230	38.1
Koc	(dm^3/g)	4.2	10.0	2.84
organic carbon	%	0.70	2.29	1.34

K: adsorption constant, equivalent units ml/g = dm³/kg; Koc: Adsorption constant as a function of the organic carbon content [ml/g = dm³/kg].

The tabulated values represent rounded results obtained by calculation used the mean values of the exact raw data.

DESORPTION

Desorption of the test substance from soils after equilibration with test article at an initial concentration of 4.06 mg/l = 406 µg absolute. Values expressed as microgram (µg) of test item and in % of the amount adsorbed.

Soil	D1		D2		Total D		%of adsorbed test item not desorbed
	µg	%	µg	%	µg	%
A (LUFA, 2.1)	10.1	2.4	< 9.3	< 2.2	< 19.4	< 4.6	> 95.4
	12.0	2.9	< 9.0	< 2.2	< 21.1	< 5.1	> 94.9
B (LUFA, 2.2)	< 9.2	< 1.9	< 9.0	< 1.9	< 18.3	< 3.8	> 96.2
	< 9.2	< 1.9	< 9.2	< 1.9	< 18.5	< 3.9	> 96.1
C (LUFA, 2.3)	7.5	1.7	< 9.2	< 2.1	< 16.7	< 3.9	> 96.1
	7.3	1.7	< 8.6	< 2.0	< 15.9	< 3.8	> 96.2

D1: amount of the test item desorbed after the first desorption step; D2: amount of the test item desorbed after the second desorption step. DTot.: total amount of the test item desorbed during both desorption steps: D1 + D2.

The test item concentration of all desorption solutions was determined to be below the quantification limit. Therefore, 0.11 µg/ml (quantification limit) were used for the further calculations.

Validity criteria fulfilled:

not specified

Conclusions:

The obtained results show that the amounts of test item adsorbed by the chosen soils ranged from 85 % (soil A) to 98 % (soil B). From these amounts less than 5 % of the total initially adsorbed amounts were desorbed.

Executive summary:

The adsorption/desorption was evaluated following internationally accepted testing guidelines (OECD 106) and the test was performed according to GLP. Adsorption and desorption of the test substance were determined on three different soils, namely a sand (soil A), a loamy sand (soil B), and a sandy loam (soil C) for a chosen test concentration of 4.91 mg/l.

Results

The obtained results show that the amounts of test item adsorbed by the chosen soils ranged from 85 % (soil A) to 98 % (soil B). From these amounts less than 5 % of the total initially adsorbed amounts were desorbed.

The Freundlich adsorption constants and their corresponding koc- values obtained were determined as follows:

Soil type	Organic carbon %	Adsorption
		k (ml/g)	koc (dm^3/g)
A. sand	0.70	29.5	4.21
B: loamy sand	2.29	230	10.0
C: sandy loam	1.34	38.1	2.84

Reference 3

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Experiment start date - 01 April 1993; Experiment end date - 16 April 1993; Study completion date - 09 June 1993.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Read-across based on grouping of substances (category approach). A detailed category justification is included in chapter 13 of this dossier.

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted May 12, 1981

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Test temperature:

Room temperature.

Analytical monitoring:

yes

Details on matrix:

SOIL TYPES
For the study three different soils differing in pH, clay content, organic matter content, and thus in cation exchange capacity were used:
Origin:
1. Soil l (Standard soil LUFA 2.1, sand)
2. Soil II (Standard soil LUFA 2.2, loamy sand)
3. Soil III (Standard soil LUFA 2.3, sandy loam)
- Source: Landwirtschaftliche Untersuchungs- und Forschungsanstalt (LUFA), D-6720 Speyer/F.RG.
- Storage: at room temperature until use.

Details on test conditions:

TEST SYSTEM
- Soil preparation: already conditioned, sieved soils (2.0 mm screen) were used for the experiment. Before experimental start the dry weight of the standard soils was determined. Therefore subsamples of approximately 15 g of each soil type were dried for 16 hours at 110 °C.

STOCK SOLUTION
- Preparation: stock solutions were prepared in the range from 99.2 µg/ml to 96.5 µg/ml by dissolving the test substance in 100 ml deionised water.
- Diluted solutions: calculated volumes of this stock solutions were diluted with deionized water to obtain standard solutions in the range from 0.19 µg/ml to 9.92 µg/ml test item.

Computational methods:

EVALUATION OF RESULTS
Injected samples were quantified by peak area with reference to the calibration curve. The latter was obtained by correlation of the peak area of the analytical standards with their corresponding concentration. The correlation is performed using a least squares fit of a linear function. The amount of the adsorbed test article in the soil was obtained by subtraction of the total amount of the test article in aqueous phase from the initial amount applied to the system. Furthermore, the adsorption constants were calculated as a function of the organic carbon content of the respective soils. The results of the screening test: adsorption values were assessed with the aid of the Freundlich adsorption equation. Desorption data are presented in % of the amount of the test item adsorbed.

Type:

Koc

Value:

1.04

% Org. carbon:

0.7

Remarks on result:

other: sand

Type:

Koc

Value:

0.86

% Org. carbon:

2.29

Remarks on result:

other: loamy sand

Type:

Koc

Value:

2.24

% Org. carbon:

1.34

Remarks on result:

other: sandy loam

Adsorption and desorption constants:

The obtained results show that the amounts of test item adsorbed by the chosen soils ranged from 58 % (LUFA 2.1, sand) to 84 % (LUFA 2.3 sandy loam). From these amounts less than 33 % (LUFA 2.1 sand) of the total initially adsorbed amounts of test item were desorbed.

Recovery of test material:

Screening adsorption: 100.6-103.3 %
Screening desorption: 112-104 %

Details on results (Batch equilibrium method):

BLANKS
No test item could be detected in the supernatants after blank tests with three soils, which were treated with deionised water without test article.

PRELIMINARY TEST
The obtained results show that the chosen chemical analysis is reproducible and satisfy.

Overview of results

	LUFA 2.2 loamy sand	LUFA 2.1 sand	LUFA 2.3 sandy loam
pH	5.8	5.9	6.6
max. water cap. (g/100 g TM)	44	26.1	35.3
Total N [%]	0.17	0.06	0.11
Organic Carbon [%]	2.29	0.7	1.34
<0.02 mm [%]	10.1	7.9	19.6
Clay (<0.002 mm) [%]	5.1	3.5	8.3
Silt (0.002-0.063 mm)[%]	2.1	1.9	3.9
Sand (0.063-2 mm) [%]	92.9	94.6	88
Cation Exchange Capacity [mval/100g]	9.7	4.9	9.5
Koc [dm^3/g]	0.86	1.04	2.24
Koc [ml/g]	860	1040	2240
logkoc	2.9	3	3.3
% of asdorbed test item not desorbed	>73.9 75.6	67.2 >72.0	>83.8 >84.0

Results obtained for the validation of the analytical method.

Nominal concentration of the test item [mg/l]	Concentration of the test item found, calc. on basis of its peak area [mg/l]	Recovery [%]
0.25	0.26 0.25	104.0 100.0
1.19	1.23 1.22	103.4 102.5
2.38	2.42 2.41	101.7 101.3
Mean		102.2 ± 1.5 SD

Results obtained for the concentrations of test substance in the blanks of the screening adsorption test.

Soil	Concentration of test item found calculated on basis of its peak area [mg/l]
A (LUFA, 2.1)	n. d./n. d.*
B (LUFA, 2.2)	n. d./n. d.*
C (LUFA, 2.3)	n. d./n. d.*

*: not detectable

CALIBRATION CURVE

The lowest practical quantification limit found was 0.25 µg/ml of the test item. Water control samples (soil A, duplicate test) were fortified with test item. The spiking levels ranged from 0.25 µg/ml to 2.38 µg/ml. A mean recovery of 102.2 % with a standard deviation of ± 1.5 % was determined. Therefore the study is considered to be valid.

RECOVERIES DURING THE STUDY

Results obtained for the recovery of the test item during the study.

Test phase	Nominal concentration of the test item [mg/l]	Concentration of the test item found, calc. on basis of its peak area [mg/l]	Recovery [%]
Screening adsorption	4.83	4.86 4.99	100.6 103.3
Screening desorption	0.25	0.28 0.26	112.0 104.0
Mean			105.0 ± 4.9 SD*

PRELIMINARY TEST

Soil	Nominal concentration of test item [mg/l]	Concentration of test item found calculated on basis of its peak area [mg/l]	Recovery [%]
A (LUFA, 2.1)	4.96	5.18 5.19	104.4 104.6
B (LUFA, 2.2)	4.96	5.12 5.26	103.2 106.0
C (LUFA, 2.3)	4.96	5.26 5.25	106.0 105.8
Mean			105.0 ±1.1 SD*

SCREENING TEST

ADSORPTION

Recovery tests without soil were performed parallel to the screening adsorption test to eliminate the influence of the test system (e. g. centrifugation tubes) on the results of the tests performed in the presence of soil. Therefore, two duplicate blank tests were performed for a concentration of 4.83 mg/l.

Results obtained for the recovery of test item without soil matrix of screening adsorption test.

Nominal concentration of test item [mg/l]	Concentration of test item found calculated on basis of its peak area [mg/l]	Recovery [%]
4.83	3.78 4.96	783.0 102.7

A significant difference to the applied amount of the test item was not found. Hence, a correction was not necessary.

Distribution of the test item between soil and aqueous phase of various soils at room temperature.

Test item conc. In aqueous medium after correction [µg/ml]	A (LUFA, 2.1)		B (LUFA, 2.2)		C (LUFA, 2.3)
	Ce [µg/ml]	x/m [µg/g]	Ce [µg/ml]	x/m [µg/g]	Ce [µg/ml]	x/m [µg/g]
4.83	2.13	14.1	1.11	21.3	0.77	23.3
	1.95	15.4	1.06	21.5	0.78	23.2

Ce: concentration of the test article in aqueous phase [µg/ml]; x/m: amount of the test article adsorbed per unit mass [g] of adsorbent.

Freundlich adsorption constants and adsorption constants as a function of the organic carbon content of various soils treated.

Parameter	Unit	Soil
		A (LUFA, 2.1)	B (LUFA, 2.2)	C (LUFA, 2.3)
Amount of the test item absorbed	%	57.8	77.6	84.0
K	(ml/g)	7.3	19.8	30.1
Koc	(dm^3/g)	1.04	0.86	2.24
organic carbon	%	0.7	2.29	1.34

K: adsorption constant, equivalent units ml/g = dm³/kg; Koc: Adsorption constant as a function of the organic carbon content [ml/g = dm³/kg]. The tabulated values represent rounded results obtained by calculation used the mean values of the exact raw data.

DESORPTION

Desorption of the test substance from soils after equilibration with test article at an initial concentration of 4.83 mg/l = 483 µg absolute. Values expressed as microgram (µg) of test item and in % of the amount adsorbed.

Soil	D1		D2		Total D		%of adsorbed test item not desorbed
	µg	%	µg	%	µg	%
A (LUFA, 2.1)	66.5	24.6	22.0	8.1	88.5	32.8	67.2
	60.6	21.0	<20.2	<7.0	<80.8	<28.0	>72.0
B (LUFA, 2.2)	81.5	21.9	<15.7	<4.2	<97.2	<26.1	>73.9
	72.8	19.3	19.2	5.1	91.9	24.4	75.6
C (LUFA, 2.3)	45.0	11.1	<20.6	<5.1	<65.7	<16.2	>83.8
	44.0	10.9	<20.7	<5.1	<64.7	<16.0	>84.0

D1: amount of the test item desorbed after the first desorption step; D2: amount of the test item desorbed after the second desorption step. DTot.: total amount of the test item desorbed during both desorption steps: D1 + D2. If the test item concentration of all desorption solutions was determined to be below the quantification limit, 0.25 µg/ml (quantification limit) were used for the further calculations.

Validity criteria fulfilled:

yes

Conclusions:

The results obtained show that the amounts of the test substance adsorbed by the chosen soils ranged from 58 % to 84 %. From these amounts, less than 33 % of the total initially adsorbed amount of the test substance were desorbed.

Executive summary:

The adsorption/desorption was evaluated following internationally accepted testing guidelines (OECD 106) and the test was performed according to GLP. Adsorption and desorption of the test substance were determined on three different soils, namely a sand (soil A), a loamy sand (soil B), and a sandy loam (soil C) for a chosen test concentration of 4.83 mg/l.

Results

The obtained results show that the amounts of test item adsorbed by the chosen soils ranged from 58 % (soil A) to 84 % (soil C). From these amounts less than 33 % (soil A) of the total initially adsorbed amounts were desorbed.

The Freundlich adsorption constants and their corresponding koc- values obtained were determined as follows:

Soil type	Organic carbon %	Adsorption
		k (ml/g)	koc (dm^3/g)
A. sand	0.70	7.3	1.04
B: loamy sand	2.29	19.8	0.86
C: sandy loam	1.34	30.1	2.24

Description of key information

The available information suggests that Stilbene Fluorescent Whitening Agents have not an univocal adsorption/desorption behaviour describable by a range of values: they are expected to be more or less mobile depending on the soil type and conditions.

Key value for chemical safety assessment

Koc at 20 °C:

10 000

Additional information

Adsorption/desorption screening with HPLC cannot technically be performed on the members of the Stilbene Fluorescent Whitening Agents category. Three studies are available for the assessment of the adsorption potential of the substances belonging to the Stilbene Fluorescent Whitening Agents category: they were performed on CAS 16090-02-1 (morpholino derivative, disulphonate), CAS 16470-24-9 (dihydroxyethylamino tetrasulphonated salt) and on CAS 68971-49-3 (dihydroxyethylamino, esasulphonated).

Results of the test performed on CAS 68971-49-3
6 Na^+	Eurosoil 5	Eurosoil 3	LUFA 2.3	Eurosoil 2	Eurosoil 4
Water solubility: 278 g/l at 20 °C pH 9
Dry Weight [%]	97.7	96.9	94.6	96.5	97.3
pH (Aqua demin.)	3.59	6.98	6.9	7.04	7.09
Organic Carbon [%]	5.96	3.01	0.64	3.72	1.31
Clay (<0.002 mm) [%]	6	17	10	22.6	20.3
Silt (0.002-0.063 mm)[%]	12.7	36.8	31	64.1	75.7
Sand (0.063-2 mm) [%]	71.6	46.4	59.1	13.4	4.1
Cation Exchange Capacity [mval/100g]	24.1	16.6	5.2	28.9	17.3
Koc [ml/g]	72.1	110	423	761	874
log Koc	1.8	2.04	2.6	2.8	2.9
Mobility	High	High	medium	low	low

Results of the test performed on CAS 16470-24-9					Results of the test performed on CAS 16090-02-1
4 Na^+	LUFA 2.3 sandy loam	LUFA 2.1 sand	LUFA 2.2 loamy sand		2 Na^+	LUFA 2.2 loamy sand	LUFA 2.1 sand	LUFA 2.3 sandy loam
Water solubility: 650 g/l at 20 °C pH 9; 406 g/l at 20 °C pH 7.9					Water solubility: 1.9 g/l at 20 °C pH 10.5
pH	6.6	5.9	5.8		pH	5.8	5.9	6.6
max. water cap. (g/100 g TM)	35.3	26.1	44		max. water cap. (g/100 g TM)	44	26.1	35.3
Organic Carbon [%]	1.34	0.7	2.29		Total N [%]	0.17	0.06	0.11
<0.02 mm [%]	19.6	7.9	10.1		Organic Carbon [%]	2.29	0.7	1.34
Clay (<0.002 mm) [%]	8.3	3.5	5.1		<0.02 mm [%]	10.1	7.9	19.6
Silt (0.002-0.063 mm)[%]	3.9	1.9	2.1		Clay (<0.002 mm) [%]	5.1	3.5	8.3
Sand (0.063-2 mm) [%]	88	94.6	92.9		Silt (0.002-0.063 mm)[%]	2.1	1.9	3.9
Cation Exchange Capacity [mval/100g]	9.5	4.9	9.7		Sand (0.063-2 mm) [%]	92.9	94.6	88
Total-N [%]	0.11	0.06	0.17		Cation Exchange Capacity [mval/100g]	9.7	4.9	9.5
Koc [dm³/g]	2.84	4.21	10		Koc [dm3/g]	0.86	1.04	2.24
Koc [ml/g]	2840	4210	10000		Koc [ml/g]	860	1040	2240
logKoc	3.4	3.6	4		logKoc	2.9	3	3.3
Mobility	slight	slight	immobile		Mobility	low	low	slight
% of asdorbed test item not desorbed	>96.1	>95.4	>96.2		% of asdorbed test item not desorbed	>73.9	67.2	>83.8
	>96.2	>94.9	>96.1			75.6	>72.0	>84.0

As all the substances belonging to the category, the test items are very soluble in water and they are characterized by a negative log kow. The experimental Koc values obtained describe different adsorption potentials: in the cases of CAS 16090-02-1 and CAS 16470-24-9 the substances can be slightly mobile to immobile. In the case of CAS 68971-49-3 the substances resulted to be high, medium and low mobile on the basis of the different soils used. The distribution of a chemical between soil and aqueous phases is a complex process depending on a number of different factors: the chemical nature of the substance, the characteristics of the soil and climatic factors such as rainfall, temperature, sunlight and wind. The increasing (or decreasing) of the mobility seems to be not clearly influenced by a particular condition assayed in the studies. Analysing the tables data, the pH is the parameter that mainly undergoes to changes related to Koc values, nevertheless its effective impact can be considered not linear. Furthermore, the pH values do not help to trace a common behaviour: in the case CAS 68971-49-3 and CAS 16090-02-1 lower pHs correspond to higher mobility, while in the case of CAS 16470-24-9 the trend resulted inverted. In the case of CAS 68971-49-3 the clay and sand soil contents seems to be related to the Koc. In all cases, the organic carbon content and the soil cation exchange capacity seem not directly influence the chemicals’ mobility. The numerous phenomena and mechanisms involved in the process of adsorption of a chemical by soil cannot be completely defined by a simplified laboratory model: the tests performed give an indication about adsorption as process of the binding of a chemical to surfaces of soils but they do not distinguish between different adsorption processes (physical and chemical adsorption) and such processes as surface catalysed degradation, bulk adsorption or chemical reaction.

No calculation of the mass balance as well as no desorption kinetic was possible during the test conducted on CAS 68971-49-3 because an accurate quantization method has not been found during the test. On the contrary, in the two studies performed with CAS 16090-021 and CAS 16470-24-9 the percentages of substance not desorbed were in the range of 67 -84 % and 94 – 96 %, respectively. The low percentage of desorption recorded during the tests can be considered as an indication that the substances under investigation are able to interact with the soil substrates chemically; however, it cannot be established the strength of this interaction. In conclusion, the available information suggests that Stilbene Fluorescent Whitening Agents have not an univocal adsorption/desorption behaviour describable by a range of values: they are expected to be more or less mobile depending on the soil type and conditions.

[LogKoc: 4.0]