Disodium 7-amino-4-hydroxy-3-[[4-[(4-sulphonatophenyl)azo]phenyl]azo]naphthalene-2-sulphonate

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

31/05/2017 - 03/07/2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

other: The method described in Rev. Toxicol. 22 (2005) 169-174 (Coeficientes de partición de hidrocarburos aromáticos policíclicos con sustancias húmicas: un método simple para su determinación)

Principles of method if other than guideline:

- Principle of test as described in the reference article: Humic substances are major components of natural water. They are acidic polymers, mostly aromatic and usually harmless. However, they play an important role because they affect bioavailability and toxicity of many compounds in aquatic environments. Polycyclic aromatic hydrocarbons (some of them carcinogenic) are considered to be some of the most common pollutants of aquatic systems. They are usually found in the environment as complex mixtures exhibiting a wide range of physical, chemical and toxicological properties. In the present work, the interaction between humic substances and phenantrene and anthracene, individually or in mixtures,was studied. Partition coefficients of the substances between dissolved organic carbon and liquid phase were estimated by a simple methodology involving solid phase extraction and UV/VIS spectrophotometry. Koc values obtained by this means are comparable with those obtained using other methods.
The method described is a valuable tool for analyzing interactions of hydrophobic pollutants with humic substances.

- Short description of test conditions: Partition coefficients of the substances between dissolved organic carbon and liquid phase were estimated by a simple methodology involving solid phase extraction and HPLC measurements.

- Parameters analysed / observed: concentration of the substance in the humic media.

GLP compliance:

no

Remarks:

Test done for screening purposes

Type of method:

HPLC estimation method

Media:

other: humic substance

Radiolabelling:

no

Details on study design: HPLC method:

EQUIPMENT
- Apparatus:
Liquid chromatograph: Agilent 1100 (Agilent Technologies)
Balance: Mettler Toledo AT261 Delta Range.
Visiprep Solid Phase Extraction Vacuum Manifolds (SUPELCO).
Software: Chemstation (Agilent Technologies).
- Type, material and dimension of analytical (guard) column: Column: Xterra RP C18 5 flm, 3.9 x 150mm (Waters).
- Detection system: PDA detector

SAMPLE PREPARATION:
Preparation of stock solutions: 10.75 mg of sample was accurately weighed and dissolved in 100.0 mL of ultrapure deionized water in a volumetric flask. The concentration of dye in the solution was 107.5 mg/L.
Standard solutions of dissolved humic substance (DHS) were prepared by dissolving 20.30 mg of Humic acid (Aldrich, Lot BCBS 1775V) in 100.0 mL of Milli Q water in a volumetric flask and after stirring for one hour on a magnetic stirrer. The solution was filtered through 0.45 flm nylon membrane.
The theoretical concentration of dissolved humic substance was 203.00 mg/L. The total organic carbon in the humic acid reference substance, determined byelemental organic analysis was 43.43%.

INTERACTION ANALYTICAL SUBSTANCES PREPARATION:
Interaction samples between the dye and the dissolved humic substance were prepared by increasing the dissolved humic substance while keeping constant the concentration of dye. Three different interaction samples (in duplicate) were prepared in Milli Q water at 3 levels of concentration DHS: 14.21,21.32 and 42.63 mg/L (corresponding to 6.17, 9.26 and 18.51 mglL of TOC). The concentration of colorant in all interaction samples was 2.002 mg/L.

EXTRACTION METHOD BY SOLID PHASE EXTRACTION:
In order to separate the free dye from interaction samples DHS-dye in the aquous mixture according to their polarity properties, a solid phase extraction was performed on a cartridge Discovery DSC-18 100 mg/1 mL (Supelco). The free dye was retained on the stationary phase and the polar fraction from interaction samples DHS-dye passed throught the caIiridge. Liquid extract containing the component of interest was injected in the chromatographic system.
All stock solutions and interaction analytical samples were stored in a refrigerator.

MOBILE PHASES
- Type:
A: H20 Milli-Q (9:1), 0.02 M Tetrabutylammonium bromide, 0.1 M KH2P04, pH 6.5 with NaOH 2N.
B: H20 Milli-Q (46.6:53.3), 0.018 M Tetrabutylammonium bromide, 0.092 M KH2P04, pH 6.5 with NaOH 2N.

Gradient:
Time (m in) 0 Solvent A (%) 25 Solvent B (%) 75
Time (m in) 10 Solvent A (%) 0 Solvent B (%) 100
Time (m in) 20 Solvent A (%) 0 Solvent B (%) 100
Time (m in) 28 Solvent A (%) 25 Solvent B (%) 75
Time (m in) 35 Solvent A (%) 25 Solvent B (%) 75

Injection: 50 µL
Flow rate: 1.0 mL/min
Detection: 515 nm

- Solutes for dissolving test and reference substances: water

REPETITIONS
- Number of determinations: 2

EVALUATION
- Determination of the log Koc value: calculation from Koc value determined in the experiment

Key result

Type:

Koc

Value:

1 330 000 L/kg

Temp.:

25 °C

Key result

Type:

log Koc

Value:

6.12 dimensionless

Temp.:

25 °C

Validity criteria fulfilled:

yes

Conclusions:

The experimental Koc value obtained for the test item is 1,33X10E6

Description of key information

The Koc and log Koc have been determined experimentally for this substance. The value of log Koc > 5 indicates that the adsorption to soil is likely to be high.

Key value for chemical safety assessment

Koc at 20 °C:

1 330 000

Additional information

[LogKoc: 6.12]