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Environmental fate & pathways

Adsorption / desorption

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Endpoint:
adsorption / desorption
Remarks:
adsorption
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Study period:
2015
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
1. SOFTWARE
EpiSuite

2. MODEL (incl. version number)
KOCWIN v2.0

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
c1(O)c(O)cc(S(=O)(=O)c2ccc(C)cc2)cc1

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
[Explain how the model fulfils the OECD principles for (Q)SAR model validation. Consider attaching the QMRF or providing a link]
See QMRF

5. APPLICABILITY DOMAIN
[Explain how the substance falls within the applicability domain of the model]
See QPRF

6. ADEQUACY OF THE RESULT
[Explain how the prediction fits the purpose of classification and labelling and/or risk assessment]
Qualifier:
according to guideline
Guideline:
other: REACH Guidance on QSARs R.6
Principles of method if other than guideline:
KOCWIN™: Formerly called PCKOCWIN™, this program estimates the organic carbon-normalized sorption coefficient for soil and sediment; i.e. KOC. KOC is estimated using two different models: the Sabljic molecular connectivity method with improved correction factors; and the traditional method based on log KOW.
Specific details on test material used for the study:
c1(O)c(O)cc(S(=O)(=O)c2ccc(C)cc2)cc1
Type:
Koc
Value:
124.7 L/kg

Koc Estimate from LogKow:

Log Kow (user entered)

1.47

Non-Corrected Log Koc (0.55313 MCI + 0.9251)

1.7382

Fragment Correction(s)

 

1 Sulfone (-C-SO2 -C)

0.0239

2 Aromatic Hydroxy (aromatic-OH)

0.3337

Corrected Log Koc

2.0958

Estimated Koc

124.7 L/kg

 

Validity criteria fulfilled:
yes
Conclusions:
Estimated Koc is 124.7 L/Kg. Substance falls within applicabllity domain of QSAR (with one minor comment (occurence of aromatic hydroxy group is present at max. 1 in training set. Substance has 2 aromatic hydroxy groups)).
Executive summary:

 

QPRF: KOCWIN v2.00 (17 Nov 2015)

 

1.

Substance

See “Test material identity”

2.

General information

 

2.1

Date of QPRF

See “Data Source (Reference)”

2.2

QPRF author and contact details

See “Data Source (Reference)”

3.

Prediction

3.1

Endpoint
(OECD Principle 1)

Endpoint

Adsorption to solid phase of soils etc.

Dependent variable

Organic carbon normalised adsorption coefficient (Koc)

3.2

Algorithm
(OECD Principle 2)

Model or submodel name

KOCWIN

Model version

v. 2.00

Reference to QMRF

QMRF: Estimation of Soil Adsorption Coefficient using KOCWIN v2.00 (EPI Suite v4.11): MCI methodology

Predicted value (model result)

See “Results and discussion”

Input for prediction

- Chemical structure via CAS number

Descriptor values

- MCI (first order molecular connectivity index)

- Correction factors

3.3

Applicability domain
(OECD principle 3)

Domains:

1) Molecular weight
(range of test data set: 32.04 to 665.02 g/mol; On-Line KOCWIN User’s Guide, Ch. 6.2.4 Domain)

Substance within range (264.3  g/mol)

2) Correction factors: Number of instances of the identified correction factor does not exceed the maximum number as listed in Appendix D (On-Line KOCWIN User’s Guide)

Not fulfilled since aromatic hydroxy bounds are maximum 1 in training set, whilst it is present twice in substance of interest. However it is determined that this influence is minor and that the prediction can be used.

3.4

The uncertainty of the prediction
(OECD principle 4)

Statistical accuracy for training dataset:

n = 516, r² = 0.916, std. dev. = 0.330, average dev. = 0.263

3.5

The chemical mechanisms according to the model underpinning the predicted result
(OECD principle 5)

Adsorption is caused by temporary (reversible) or permanent bonding between the substance and a surface (e.g. due to van der Waals interactions, hydrogen bonding to hydroxyl groups, ionic interactions, covalent bonding, etc.). The organic carbon normalized adsorption coefficient (Koc) is the ratio of a substance concentration sorbed in the organic matter component of soil or sediment to that in the aqueous phase at equilibrium.

MCI methodology: The first-order molecular connectivity index is a measure to describe a variety of properties of chemicals. According to Sabljic (1984; cited in Meylan et al., 1992), the soil sorption potential is highly correlated with the first order MCI. Therefore, it has been used to derive the adsorption coefficient.

 

References

- US EPA (2012). On-Line KOCWIN User’s Guide.

- Meylan, W., P.H. Howard and R.S. Boethling. 1992. Molecular topology/fragment contribution method for predicting soil sorption coefficients. Environ. Sci. Technol. 26: 1560-1567.

 

 

Assessment of estimation domain (molecular weight, fragments, correction factors):

 

Appendix D. MCI & Log Kow Correction Factors for 447 Compound Training Set

Correction

Factor

Descriptor

Coefficient for Molecular

Connectivity Index

(MCI) Regression

Methodology

Occurrence

No. of instances
of each bond
found for the
current substance 

(new model)

 Remark

(number of

compounds

(max per

structure)

1 Sulfone (-C-SO2 -C-)

-1.314

(a)

10

2

1

2 Aromatic Hydroxy (aromatic-OH)

-0.0966

 

27

1

2

 (a) Counted up to twice per structure, regardless of number of occurrences.

Endpoint:
adsorption / desorption: screening
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Study period:
2020
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
[Please provide information for all of the points below. Indicate if further information is included as attachment to the same record, or elsewhere in the dataset (insert links in 'Cross-reference' table)]

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
[Describe why the read-across can be performed (e.g. common functional group(s), common precursor(s)/breakdown product(s) or common mechanism(s) of action]

See attached documents.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
[Provide here, if relevant, additional information to that included in the Test material section of the source and target records]
See attached documents.


3. ANALOGUE APPROACH JUSTIFICATION
[Summarise here based on available experimental data how these results verify that the read-across is justified]
See attached documents.

4. DATA MATRIX
See attached documents.
Reason / purpose for cross-reference:
read-across source
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))
Version / remarks:
March 04, 2016
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:
January 22, 2001
GLP compliance:
yes
Type of method:
HPLC estimation method
Media:
sewage sludge
Radiolabelling:
no
Type:
log Koc
Value:
1.39 dimensionless
pH:
7
Remarks on result:
other: Test item – peak 1 (96.1 area under curve)
Type:
log Koc
Value:
2.82 dimensionless
pH:
7
Remarks on result:
other: Test item – peak 2 (3.9% area under curve)
Type:
log Koc
Value:
1.24 dimensionless
pH:
2
Remarks on result:
other: Test item – peak 1 (96.4% area under curve)
Type:
log Koc
Value:
3.58 dimensionless
pH:
2
Remarks on result:
other: Test item – peak 2 (3.6% area under curve)

pH 7

In the chromatogram of the test solution, one major peak and one small test item peaks were observed.

 

The results of the HPLC method are given in Table 10.

The equation of the regression line was: log k’ = 0.418´log Koc– 1.049 (r = 0.98, n = 12).

 

Table 10        pH 7: Koc of the Test Item

Substance

Retention time (min)

log Koc

Koc

Peak area
(%)

tr,1

tr,2

mean

Formamide (t0)

0.721

0.720

0.721

 

 

 

Acetanilide

0.948

0.948

0.948

1.26

 

 

Monuron

1.172

1.174

1.173

1.99

 

 

2,5-Dichloroaniline

1.325

1.328

1.327

2.55

 

 

Naphthalene

1.557

1.556

1.557

2.75

 

 

Benzoic acid phenylester

1.862

1.864

1.863

2.87

 

 

Fenthion

2.407

2.421

2.414

3.31

 

 

Test item – peak 1

0.966

0.967

0.967

1.39

2.5´101

96.1

Test item – peak 2

1.682

1.690

1.686

2.82

6.5´102

3.9

 

pH 2

In the chromatogram of the test solution, one major peak and one small test item peak were observed.

 

The results of the HPLC method are given in Table 11.

The equation of the regression line was: log k’ = 0.319´log Koc– 0.815 (r = 0.98, n = 14).

 

Table 11        pH 2: Koc of the Test Item

Substance

Retention time (min)

log Koc

Koc

Peak area
(%)

tr,1

tr,2

mean

Formamide (t0)

0.727

0.726

0.727

 

 

 

Acetanilide

0.956

0.957

0.957

1.26

 

 

Monuron

1.176

1.175

1.176

1.99

 

 

Naphthalene

1.561

1.565

1.563

2.75

 

 

Benzoic acid phenylester

1.834

1.834

1.834

2.87

 

 

Fenthion

2.479

2.479

2.479

3.31

 

 

Phenanthrene

2.739

2.741

2.740

4.09

 

 

4,4’-DDT

6.759

6.755

6.757

5.63

 

 

Test item – peak 1

1.003

1.004

1.004

1.24

1.7´101

96.4

Test item – peak 2

2.263

2.267

2.265

3.58

3.8´103

3.6

Validity criteria fulfilled:
yes
Conclusions:
For a structural analogue (CH03951), the HPLC method using soil-adsorption-reference data was applied for the determination of the adsorption coefficient (Koc). The log Koc values for CH04008 are expected to be similar.

The Koc and log Koc values of the test item at neutral pH and pH 2 were:
neutral pH pH 2
Koc log Koc Peak area (%) Koc log Koc Peak area (%)
Test item – peak 1 2.5 * 10^1 1.39 96.1 1.7 * 10^1 1.24 96.4
Test item – peak 2 6.5 * 10^2 2.82 3.9 3.8 * 10^3 3.58 3.6
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2020
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))
Version / remarks:
March 04, 2016
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:
January 22, 2001
GLP compliance:
yes
Type of method:
HPLC estimation method
Media:
sewage sludge
Radiolabelling:
no
Details on study design: HPLC method:
Instrument Acquity UPLC system
(Waters, Milford, MA, USA)
Detector Acquity UPLC TUV detector (Waters)
Column Acquity UPLC HSS Cyano,
100 mm  2.1 mm i.d., dp = 1.8 µm (Waters)
Column temperature 35°C  1°C
Injection volume 5 µL
Mobile phase for study at pH 7 55/45 (v/v) methanol/buffer pH 7
Mobile phase for study at pH 2 55/45 (v/v) methanol/water pH 2
Flow 0.4 mL/min
UV detection 210 nm

Reference substance and test item solutions were injected in duplicate. Blank solutions were analyzed by single injection.

* Preparation of Solutions pH 7
Reference Substances
Reference substance Purity CAS number Supplier log Koc
Acetanilide > 99.9% 103-84-4 Sigma-Aldrich 1.26
Monuron 99.9% 150-68-5 Sigma-Aldrich 1.99
2,5-Dichloroaniline 99.9% 95-82-9 Sigma-Aldrich 2.55
Naphthalene 100% 91-20-3 Sigma-Aldrich 2.75
Benzoic acid phenylester > 99.9% 93-99-2 Sigma-Aldrich 2.87
Fenthion 98.6% 55-38-9 Sigma-Aldrich 3.31

log Koc values according to the OECD 121 guideline based on soil adsorption data.

* Preparation of Solutions pH 2
Reference Substances
Reference substance Purity CAS number Supplier log Koc 1
Acetanilide > 99.9% 103-84-4 Sigma-Aldrich 1.26
Monuron 99.9% 150-68-5 Sigma-Aldrich 1.99
Naphthalene 100% 91-20-3 Sigma-Aldrich 2.75
Benzoic acid phenylester > 99.9% 93-99-2 Sigma-Aldrich 2.87
Fenthion 98.6% 55-38-9 Sigma-Aldrich 3.31
Phenanthrene 98.5% 85-01-8 Acros Organics 4.09
4,4’-DDT 98.7% 50-29-3 Sigma-Aldrich 5.63

Log Koc values according to the OECD 121 guideline based on soil adsorption data.
Type:
log Koc
Value:
1.39 dimensionless
pH:
7
Remarks on result:
other: Test item – peak 1 (96.1 area under curve)
Type:
log Koc
Value:
2.82 dimensionless
pH:
7
Remarks on result:
other: Test item – peak 2 (3.9% area under curve)
Type:
log Koc
Value:
1.24 dimensionless
pH:
2
Remarks on result:
other: Test item – peak 1 (96.4% area under curve)
Type:
log Koc
Value:
3.58 dimensionless
pH:
2
Remarks on result:
other: Test item – peak 2 (3.6% area under curve)

pH 7

In the chromatogram of the test solution, one major peak and one small test item peaks were observed.

 

The results of the HPLC method are given in Table 10.

The equation of the regression line was: log k’ = 0.418´log Koc– 1.049 (r = 0.98, n = 12).

 

Table 10        pH 7: Koc of the Test Item

Substance

Retention time (min)

log Koc

Koc

Peak area
(%)

tr,1

tr,2

mean

Formamide (t0)

0.721

0.720

0.721

 

 

 

Acetanilide

0.948

0.948

0.948

1.26

 

 

Monuron

1.172

1.174

1.173

1.99

 

 

2,5-Dichloroaniline

1.325

1.328

1.327

2.55

 

 

Naphthalene

1.557

1.556

1.557

2.75

 

 

Benzoic acid phenylester

1.862

1.864

1.863

2.87

 

 

Fenthion

2.407

2.421

2.414

3.31

 

 

Test item – peak 1

0.966

0.967

0.967

1.39

2.5´101

96.1

Test item – peak 2

1.682

1.690

1.686

2.82

6.5´102

3.9

 

pH 2

In the chromatogram of the test solution, one major peak and one small test item peak were observed.

 

The results of the HPLC method are given in Table 11.

The equation of the regression line was: log k’ = 0.319´log Koc– 0.815 (r = 0.98, n = 14).

 

Table 11        pH 2: Koc of the Test Item

Substance

Retention time (min)

log Koc

Koc

Peak area
(%)

tr,1

tr,2

mean

Formamide (t0)

0.727

0.726

0.727

 

 

 

Acetanilide

0.956

0.957

0.957

1.26

 

 

Monuron

1.176

1.175

1.176

1.99

 

 

Naphthalene

1.561

1.565

1.563

2.75

 

 

Benzoic acid phenylester

1.834

1.834

1.834

2.87

 

 

Fenthion

2.479

2.479

2.479

3.31

 

 

Phenanthrene

2.739

2.741

2.740

4.09

 

 

4,4’-DDT

6.759

6.755

6.757

5.63

 

 

Test item – peak 1

1.003

1.004

1.004

1.24

1.7´101

96.4

Test item – peak 2

2.263

2.267

2.265

3.58

3.8´103

3.6

Validity criteria fulfilled:
yes
Conclusions:
The HPLC method using soil-adsorption-reference data was applied for the determination of the adsorption coefficient (Koc) of CH03951.

The Koc and log Koc values of the test item at neutral pH and pH 2 were:
neutral pH pH 2
Koc log Koc Peak area (%) Koc log Koc Peak area (%)
Test item – peak 1 2.5 * 10^1 1.39 96.1 1.7 * 10^1 1.24 96.4
Test item – peak 2 6.5 * 10^2 2.82 3.9 3.8 * 10^3 3.58 3.6

Description of key information

Koc is estimated to be 124.7 L/Kg (Log Koc= 2.095). The log Koc of a structural analogue (CH03951) was similar (log Koc = 1.39). Therefore, the log Koc of 2.09 was retained.

Key value for chemical safety assessment

Koc at 20 °C:
124.7

Additional information

[LogKoc: 2.095]