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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
December 06, 1996 to March 12, 1997
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)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
Swiss GLP
Type of method:
batch equilibrium method
Media:
soil
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: WP2/96
- Expiration date of the lot/batch: November 30, 2004

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Away from direct sunlight, at room temperature (approx. 20 °C)
- Stability under test conditions: Stable under storage conditions
- Solubility of the test substance in the solvent/vehicle: About 5 g/l (20 °C) in water.
Radiolabelling:
not specified
Test temperature:
20 °C
Details on study design: HPLC method:
The aqueous phases of all tubes were analysed for parent concentration. Standard solutions were analysed before and after a series of samples at each sampling. For each series a linear regression
curve was calculated using the standard solution concentrations and the corresponding peak areas. With this linear regression curve the concentrations in the aqueous samples were calculated.

Operating Conditions
Precolumn: 4 • 4 mm, 5 µm, Li Chrospher 100 (Merck), C-18
Column: 25 cm • 4.6 mm, 5 µm Supelcosil LC-18 DB
Flow: 1 ml/minute
Mobile phase: Solvent A: Titrisol buffer, pH 7 (Merck)* ; Solvent B: Acetonitrile

Injection: 50 µl
Instrument
Autosampler: Merck-Hitachi AS 2000 A
Pump: Merck-Hitachi L 6200 A
UV-Detector: Merck-Hitachi L 4000 (at 250 nm)

*1 ampoule per 2.5 I H20 (dilution factor 5).
Analytical monitoring:
yes
Details on sampling:
Sample aliquots of the CaCI2 solutions were taken 16 h after addition of FAT 45'176/A (5.04 mg FAT 45'176/A per litre CaCI2 solution) and were analysed for parent compound by HPLC. The three blanks and the control samples were subjected to the same adsorption step as the test samples. No stability for a single component was determined, but for the whole sample it can be stated that the entire amount was found in the control tubes after five days.
Details on matrix:
The screening test was performed in duplicate at a concentration of 5.04 mg/l using the three soil types. Blanks were included for each of the three soils containing only 0.01 mol CaCI2 per litre solution (no test chemical) and a single control of the test substance solution with no soil, to determine if the chemical adsorbed to the container.
Details on test conditions:
Adsorption of the Test Substance to Soils
After adsorption the tubes were weighed to determine the total volume of CaCI2 solution exposed to the soil during adsorption. The soils were centrifuged at about 20 °C for 10 minutes at 2000 rpm/870 x gmax. Following centrifugation the aqueous phases were removed as completely as possible. The volumes of the supernatants were determined gravimetrically. The aqueous solutions were analysed immediately for parent compound. The equilibrium concentration of the test substance, where possible, and its total amount in the aqueous phase was calculated.
Desorption of the Test Substance from Soils
The remaining soil samples were weighed to determine the amount of water retained. The precise determination of residual water is important in order to know the concentration of parent in the residual water. Thus, the initial amount present before the first desorption consists of the parent adsorbed to the soil and parent in residual water. Thereafter, 25 ml of untreated 0.01 mol CaCI2 per litre solution was added and the mixture shaken for 16 hours. After shaking, the mixture was centrifuged at about 20 °C and the supernatant analysed for parent concentration.
Type:
Koc
Value:
1 105 other: ml/g
Temp.:
20 °C
% Org. carbon:
2.29
Remarks on result:
other: Speyer
Type:
Koc
Value:
1 156 other: ml/g
Temp.:
20 °C
% Org. carbon:
1.57
Remarks on result:
other: Sisseln
Type:
Koc
Value:
1 249 other: ml/g
Temp.:
20 °C
% Org. carbon:
3.8
Remarks on result:
other: Les Barges
Details on results (HPLC method):
All HPLC chromatograms were evaluated by integrating a range of peaks corresponding to the composition of the test substance. Different concentrations of the test substance showed linear correlation to the sum of the peak areas (cf. 2.5. Quantification).
Adsorption and desorption constants:
The adsorption coefficients K' for FAT 45'176/A in soils Speyer, Sissein and Les Barges were 25.30 ml/g, 18.15 ml/g and 47.45 ml/g, respectively.
Recovery of test material:
no data
Concentration of test substance at end of adsorption equilibration period:
Sissein: 1.06 and 1.05 mg/l for sample 1 and 2, respectively
Speyer: 0.81 and 0.81 mg/l for sample 1 and 2, respectively
Les Barges: 0.47 and 0.46 mg/l for sample 1 and 2, respectively
Concentration of test substance at end of desorption equilibration period:
Sissein: 0.95 and 1.04 mg/l for sample 1 and 2, respectively
Speyer: 0.93 and 0.94 mg/l for sample 1 and 2, respectively
Les Barges: 1.08 and 1.14 mg/l for sample 1 and 2, respectively
Transformation products:
not specified
Details on results (Batch equilibrium method):
Soils Speyer, Sissein and Les Barges adsorbed 82.05 %, 77.30 % and 89.89 %, respectively, of FAT 45'176/A within 16 h. After adsorption, two desorption steps were performed. From the substance adsorbed, 16.73 %, 23.83 % and 24.03 % from soils Speyer, Sissein and Les Barges could be desorbed.
Statistics:
no data

To determine the stability, a solution of about 5 mg/l FAT 45'176/A in 0.01 M CaCl2 was prepared. This solution remained stable for at least five days.

Validity criteria fulfilled:
yes
Conclusions:
The K'oc values show that FAT 45'176/A is little mobile in soils.
Executive summary:

The adsorption and desorption of FAT 45'176/A were determined according to OECD 106 guideline. A screening test by the batch equilibrium method using three soils: Speyer (loamy sand), Les Barges (silt loam) and Sisseln (sandy loam). The soils chosen represented a range of organic carbon content, pH, cation exchange capacity and clay content. The screening test revealed a strong adsorption of FAT 45'176/A on soils. At a concentration of 5.04 mg/l and soil samples of 5 g, the amount of FAT 45'176/A adsorbed was 82.05 % for soil Speyer, 77.30 % for soil Sissein and 89.89 % for soil Les Barges. After two desorption steps, 16.73 %, 23.83 % and 24.03 % of the substance adsorbed from soils Speyer, Sissein and Les Barges could be desorbed.

The adsorption coefficient was 25.30 ml/g, 18.15 ml/g and 47.45 ml/g calculated for soils Speyer, Sisseln and Les Barges, and the corresponding KOC values were 1105 ml/g, 1156 ml/g and 1249 ml/g, respectively. FAT 45'176/A can therefore be regarded as little mobile in soils.

Description of key information

Reactive Orange 136 can be regarded as little mobile in soils.

Key value for chemical safety assessment

Koc at 20 °C:
1 170

Additional information

The adsorption and desorption of FAT 45'176/A were determined according to OECD 106 guideline. A screening test by the batch equilibrium method using three soils: Speyer (loamy sand), Les Barges (silt loam) and Sisseln (sandy loam). The soils chosen represented a range of organic carbon content, pH, cation exchange capacity and clay content. The screening test revealed a strong adsorption of FAT 45'176/A on soils. At a concentration of 5.04 mg/l and soil samples of 5 g, the amount of FAT 45'176/A adsorbed was 82.05 % for soil Speyer, 77.30 % for soil Sissein and 89.89 % for soil Les Barges. After two desorption steps, 16.73 %, 23.83 % and 24.03 % of the substance adsorbed from soils Speyer, Sissein and Les Barges could be desorbed.

The adsorption coefficient was 25.30 ml/g, 18.15 ml/g and 47.45 ml/g calculated for soils Speyer, Sisseln and Les Barges, and the corresponding KOC values were 1105 ml/g, 1156 ml/g and 1249 ml/g, respectively. FAT 45'176/A can therefore be regarded as little mobile in soils.