Reaction products of disodium 3,5-diamino-2-[(2-sulfonatophenyl)diazenyl]benzoate and  diazotised sodium 2-[(4-aminophenyl)sulfonyl]ethyl sulfate

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:

Experiment start and end date - 13 June 2003; Study completion date - 11 July 2003.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.19 (Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge Using High Performance Liquid Chromatography (HPLC))

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Media:

soil/sewage sludge

Specific details on test material used for the study:

Identity: FAT 40810/A
Batch: WP 6/02
Purity: approx. 75 %
Appearance: Solid, dark brownish powder
Expiration date: 12 December 2010
Storage: At room temperature at about 20 °C

Radiolabelling:

not specified

Test temperature:

Room temperature (approx. 20 °C)

Details on study design: HPLC method:

Principle
For the estimation of the adsorption coefficient, the HPLC-method was used. Therefore, an analytical column packed with a commercially available, cyanopropyl solid phase containing Iipophilic and polar moieties was used. A moderately polar stationary phase based on a silica matrix was used. While passing through the column along with the mobile phase, the test item interacts with the stationary phase. As a result of partitioning between mobile and stationary phases, the test item is retarded. The dual composition of the stationary phase having polar and non-polar sites allows for interaction of polar and non-polar groups of a molecule in a similar way as is the case for organic matter in soil or sewage sludge matrices. This enables the relationship between the retention time on the column and the adsorption coefficient on organic matter to be established.
Definitions
Kd: Distribution coefficient defined as the ratio of equilibrium concentrations Ce of a dissolved substance in a two-phase system consisting of a solid (soil or sewage sludge) and an aqueous phase; it is a dimensionless value varying with solid properties.
Kd = Csoil_sludge/Cwater .
C = Concentration of the test item at equilibrium (µg/g)
Koc: Distribution coefcient (Kd) normalised to the organic carbon content (OC) of a solid; particularly for non-ionised chemicals, it is an approximate indicator for the strength of adsorption between a substance and the solid and allows comparisons to be made between different chemicals.
KOC = Kd/OC (dimensionless)
The adsorption coefficient (KOC) is deduced from the capacity factor (k‘) using a calibration plot of log k’ versus log KOC of the selected reference items.
k’ = (tr – to)/to
tr = HPLC retention time of test or reference items (min.)
to = HPLC dead time (min.) (measurement of the retention time of sodium nitrate)
The adsorption coefficient (KOC) of the test item will be interpolated from the calibration curve which will be established by correlation of the log Koc values of various reference items with their log k‘ values.

Analytical monitoring:

yes

Details on sampling:

not applicable (HPLC method)

Details on matrix:

see details on analytics (HPLC column)

Details on test conditions:

Test Item Solution
FAT 40810/A (15.2 mg) was dissolved in methanol (10 ml) to prepare a stock solution of 1520 µg/ml. The stock solution (1 ml) was diluted with methanol to 20 ml to obtain a standard solution of 76 µg/ml. The pH value of the test item solution was determined to be 7.3. The test item solution was injected three times.

Reference Solutions
The reference items were chosen from the list given in the OECD Guideline No. 121 and EC Directive C.19. Stock solutions of the reference items in methanol were prepared as described:
11.4 mg of the reference item phenol, 10.3 mg of the reference item Isoproturon, 11.1 mg of the reference item linuron, 10.4 mg of the reference item 2.4-DDT, 12.0 mg of the reference item pyrazophos and 11.5 mg of the reference item diclofop-methyl were each dissolved in 10 ml methanol. A combined reference solution was prepared by transferring 133 µl of the phenol stock solution, 190 µl of the Isoproturon, 120 µl of the linuron, 1430 µl of the pyrazophos, 275 µl of the diclofop-methyl and 1050 µl of the 2.4-DDT stock solution into one volumetric flask and diluting to a volume of 10 ml with a mixture of water and methanol (45:55; v/v). This reference solution was injected six times. Sodium nitrate (27.5 mg) was diluted to 100 ml with methanol to obtain a stock solution. The stock solution (100 µl) was diluted to 1 ml with a solvent mixture of water and methanol (45:55; v/v). This sodium nitrate solution was injected two times for the determination of the dead time of the HPLC system.

Type:

log Koc

Value:

< 1.32

Temp.:

20 °C

Remarks on result:

other: pH not measured

Details on results (HPLC method):

The determination of the adsorption coefficient (Koc) of FAT 40810/A was performed according to the OECD Guideline for the Testing of Chemicals, No. 121, Estimation of the Adsorption Coefficient (Koc) on Soil and Sewage Sludge using High Performance Liquid Chromatography (HPLC), January, 2001 and the EC Directive 2001/59, C.19. The test item solution was injected three times and the combined reference solution was injected six times. The log Koc was calculated using a regression curve (log k‘ vs. log Koc) and was found to be <1.32 which is equal to a Koc value of <21. The retention time of the test item solution was shorter than the retention time of the lowest retention time of the reference item phenol (Koc = 21; log Koc = 1.32). In the present study the reference items covered the range of log Koc 1.32 to log Koc 5.63.
The chromatography of the test item resulted in one main peak with a well-defined and reproducible retention time. The HPLC method was therefore considered to be suitable for the purpose of the study. Based on the chromatographic data, FAT 40810/A was considered to be stable during the test procedure. The retention times of the individual measurements of the reference items, test item and the dead time are given in provided tables. The capacity factor (k‘) was calculated for each reference item using the retention times. Log Koc was plotted versus log k for each component to obtain a regression curve. The tabulated values represent rounded mean results, which were obtained by calculation using the exact raw data. In conclusion, the log of the adsorption coefficient (Koc) of FAT 40810/A was estimated to be log Koc <1.32 which is equal to a Koc value of <21 using the HPLC method. This value indicates that FAT 40810/A is mobile and will not be absorbed by organic carbon in soil.

Validity criteria fulfilled:

yes

Conclusions:

Result for FAT408190/A: log Koc <1.32 (equivalent to Koc <21)

Executive summary:

The determination of the adsorption coefficient (Koc) of FAT 40810/A was performed according to the OECD Guideline No. 121 and the EC Directive 2001/59, C.19. in a GLP certified laboratory. HPLC was used for estimation of Koc and Log Koc. The log Koc was calculated using a regression curve (log k' vs. log Koc). Based on the findings of this study, the log Koc was determined to be <1.32 and Koc was determined to be <21.

Description of key information

The determination of the adsorption coefficient (Koc) of FAT 40810/A was performed according to the OECD Guideline No. 121 and the EC Directive 2001/59, C.19. in a GLP certified laboratory. HPLC was used for estimation of Koc and Log Koc. The log Koc was calculated using a regression curve (log k' vs. log Koc). Based on the findings of this study, the log Koc was determined to be <1.32 and Koc was determined to be <21.

Key value for chemical safety assessment

Koc at 20 °C:

21