Hexasodium 2,2'-[vinylenebis[(3-sulphonato-4,1-phenylene)imino[6-[(2-cyanoethyl)[2-(2-hydroxyethoxy)ethyl]amino]-1,3,5-triazine-4,2-diyl]imino]]bis[benzene-1,4-disulphonate]

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

March from the 22th to the 29th, 2004

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Justification for type of information:

Justification for read across is detailed in section 13.

Reason / purpose for cross-reference:

read-across source

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))

Version / remarks:

adopted in January, 2001

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))

GLP compliance:

yes

Type of method:

HPLC estimation method

Media:

soil/sewage sludge

Test temperature:

25 °C

Details on study design: HPLC method:

TEST ITEM SOLUTION
The test item (31.29 mg) was dissolved in 100 ml methanol with aid of sonication to prepare a stock solution of 312.9 µg/ml. 2.5 ml of the stock solution were diluted with methanol to 50 ml to obtain a standard solution of 15.645 µg/ml.

EQUIPMENT
- Column: LiChrospher 100 CN, part. size 51 µm, 250 mm x 4 mm.
- Mobile phase: acetonitrile / 0.01 M citrate buffer solutiion (55:45; v/v).
- Mobile phase pH: 6.02
- Mobile phase temperature: 25 °C
- Injection volume: 20 µl
- Flow: 1.0 ml/min
- Detection system: UV-VIS detector; 350 nm for the test item and 2 0 nm for reference item and for sodium nitrate.

REFERENCE SUBSTANCES
- Identity: acetanilide, isoproturon, linuron, pyrazophos, diclofop-methyl, 2,4-DDT, sodium nitrate

REPETITIONS
- Number of determinations: the test item solution was injected three times and the reference item solutions were injected six times.

Type:

Koc

Value:

< 18 dimensionless

Remarks on result:

not determinable because of methodological limitations

Type:

Koc

Remarks:

estimated by QSAR

Value:

12 dimensionless

Remarks on result:

other: average of regression equations

Details on results (HPLC method):

Sodium nitrate that was used for the dead time determination was eluted at a retention time of about 2.29 minutes.
The test item was found to elute as two peaks at a retenton times of about 1.46 and 2.24 minutes.
The reference item with the lowest Koc was eluted at a retention time of about 3.16 minutes.
Since the test item was was not retained under the chromatographic conditions of the test and was eluted at the dead time, its Koc was determined to be lower than that one of the lowest reference item acetanilide.

Retention times in minutes of the reference items and the test item

	Run 1	Run 2	Run 3	Run 4	Run 5	Run 6
Sodium nitrate (dead time)	2.29	2.3	2.29
Reference items
Acetanilide	3.16	3.17	3.17	3.17	3.16	3.16
Isoproturon	3.93	3.94	3.93	3.94	3.93	3.93
Linuron	4.54	4.56	4.55	4.56	4.55	4.55
Pyrazophos	5.58	5.59	5.59	5.6	5.58	5.58
Diclofop-methyl	6.69	6.71	6.7	6.71	6.7	6.7
2,4-DDT	8.72	8.74	8.73	8.75	8.73	8.74
Test substance
Peak 1	1.46	1.46	1.46
Peak 2	2.26	2.24	2.23

Estimated Koc values from QSAR regression equations

Estimation method	Koc
Regression I	4
Regression II	48
Regression III	18
Regression IV	24
Regression V	1
Regression VI	1
Regression VII	2
Regression VIII	1
Regression IX	7
Average Koc (all regression)	12

Conclusions:

Koc <18 (logKoc <1.25)

Executive summary:

The determination of the adsorption coefficient was performed according to the OECD no. 121 (HPLC). The exact Koc value of the test substance could not be measured, since it was not retained under the chromatographic conditions of the test and was eluted at the dead time. Therefore, the Koc of the test substance was determined to be lower than the one of the lowest reference item acetanilide, i.e. <18 (or logKoc <1.25). In addition, in order to consolidate the findings, a QSAR estimation using different appropriate regression equations was performed, reporting an average Koc of 12.

Discussion and conclusion

Despite the determined adsorption coefficient value (logKoc <1.25) is slightly outside the applicability domain of the followed guideline (logKoc range from 1.5 to 5.0), the result in any case can be considered to adequately represent the soil-adsorption property. In fact, the Koc value is extremely low, suggesting that the substance is mobile in soli.

Koc <18 (logKoc <1.25)

Description of key information

Koc <18 (log Koc < 1.25)

Key value for chemical safety assessment

Koc at 20 °C:

12

Additional information

The substance resulted to be water soluble (solubility higher than 100 g/l) and the logPow was estimated to be lower than -2.

Since no experimental data is available for Optical Brightener 380, the information on the structural analogous Similar Substance 01 have been taken into consideration to investigate the adsorption potential. The read across approach can be considered reliable and appropriate to investigate the property (details for the approach are included into the IUCLID section 13).

The determination of the adsorption coefficient of Similar Substance 01 was performed according to the OECD no. 121 (HPLC). The exact Koc value of the test substance could not be measured, since it was not retained under the chromatographic conditions of the test and was eluted at the dead time. Therefore, the Koc of the test substance was determined to be lower than the one of the lowest reference item acetanilide, i.e. <18 (or logKoc <1.25). In addition, in order to consolidate the findings, a QSAR estimation using different appropriate regression equations was performed, reporting an average Koc of 12.

Despite the determined adsorption coefficient value resulted to be outside of the applicability domain of the followed guideline, the result can be considered as adequately representative and the estimated value has been used as representative for Optical Brightener 380. Accordingly, the suspended matter-water and soil-water partition coefficients were estimated, using EUSES v.2.1.2, for completeness sake.

Suspended matter-water partition coefficient: 15.8 (log K_susp: 1.2)

Soil-water partition coefficient: 3.6 (log K_soil: 0.56)