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Adsorption / desorption

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Endpoint:
adsorption / desorption: screening
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Study period:
2004-06-08 to 2004-06-23
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP study performed according to OECD 121 without major deviations. On analogue substance.
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))
Deviations:
yes
Remarks:
The log Koc of one of the six reference compounds (2-nitrobenzamide) was taken from the literature (Gawlik and Muntau, 1999).
GLP compliance:
yes (incl. certificate)
Type of method:
HPLC estimation method
Media:
soil/sewage sludge
Test material information:
Composition 1
Radiolabelling:
no
Test temperature:
room temperature (kept constant via air conditioning)
Details on study design: HPLC method:
EQUIPMENT- Apparatus: Analytical HPLC column (based on silica matrix) packed with a cyanopropyl (CN-) solid phase containing non-polar and polar moieties. - Type: HPLC-column: CC250/3 NUCLEOSIL 100-5 CN, MACHEREY-NAGEL; Pre-column: CC8/3 NUCLEOSIL 100-5 CN, MACHEREY-NAGEL - Type, material and dimension of analytical (guard) column: column was packed with a cyanopropyl (CN-) solid phase containing non-polar and polar moeities- Detection system: Diode Array Dector (DAD)MOBILE PHASES- Type: Methanol: citrate- buffer pH 6.0/55:45 (v/v) and Methanol: citrate- buffer pH 3.0/55:45 (v/v) - Experiments with additives carried out on separate columns: no data- pH: 3.0 and 6.0- Solutes for dissolving test and reference substances: HPLC water (test substance and NaNO3) or methanol (reference items)DETERMINATION OF DEAD TIME - Method: A three-fold determination of dead time was performed with a solution of 5 mg/L NaNO3 in mobile phase pH 3 and pH 6. Mean values were calculated.REFERENCE SUBSTANCES- Identity: 2-Nitrobenzamide- Identity: Atrazine- Identity: Triadimenol- Identity: Pyrazophos- Identity: alpha-Endosulfan- Identity: 4,4'-DDTDETERMINATION OF RETENTION TIMES- Quantity of test substance introduced in the column: injection volume= 30 uL- Quantity of reference substances: three injections, 5 mg/L (nominal concentration), injection volume= 30 uL- Intervals of calibration: Calibration of the method by determination of the retention times of the six reference items at pH 3 and 6 occurred separately before and after the analysis of the test substance to confirm constant retention times during the measurement.REPETITIONS- Number of determinations: test substance: triplicate; reference items: 2; NaNO3: 3EVALUATION- Calculation of capacity factors k': capacity factor (k')= (retention time-dead time)/dead time- Calculation of retention times: No data- Determination of the log Koc value: By means of the adsorption coefficient values (Koc) and the corresponding capacity factors of the reference items, a calibration graph of log Koc vs. log k' was plotted. The log k' value of the test substance was then used to calculate its log Koc value via the equation of the linear regression curve from the calibration graph.
Type:
Koc
Value:
1.19
Remarks on result:
other: pH3
Type:
Koc
Value:
17.3
Remarks on result:
other: pH6
Type:
log Koc
Value:
0.076
Remarks on result:
other: pH3
Type:
log Koc
Value:
1.24
Remarks on result:
other: pH6
Details on results (HPLC method):
-Adsorption coefficients (Koc): pH 3: 1.19 +/- 0.02, pH 6: 17.3 +/- 0.0-log Koc: pH 3: 0.0764 +/- 0.0099, pH 6: 1.24 +/- 0.0- Retention times of reference substances used for calibration: At pH 3- 2-Nitrobenzamide: 3.693 min.- Atrazine: 4.118 min.- Triadimenol: 4.510 min.- Pyrazophos: 5.581 min.- alpha-Endosulfan: 5.594 min.- 4,4'-DDT: 7.639 min. At pH 6- 2-Nitrobenzamide: 3.697 min.- Atrazine: 4.127 min.- Triadimenol: 4.561 min.- Pyrazophos: 5.648 min.- alpha-Endosulfan: 5.696 min.- 4,4'-DDT: 7.837 min. - Details of fitted regression line (log k' vs. log Koc): At pH 3: y = 0.1754x - 0.7824; R-squared= 0.985At pH 6: y = 0.1513x - 0.5761; R-squared= 0.9915- Average retention data for test substance: At pH 3: 3.589 +/-0.003At pH 6: 3.908 +/-0.001
Statistics:
N/A

Dead time at pH 3= 3.067 +/- 0.013, at pH 6= 2.775 +/- 0.008

The validity critera were fullfilled.

According to the McCall classification scheme of soil mobility potential a Koc of 1.19 (pH 3) and of 17.3 (pH 6) would indicate a very high mobility for the test substance.

Validity criteria fulfilled:
yes
Conclusions:
The log Koc for the test substance was at pH 3: 0.076 ± 0.010, corresponding to a Koc of 1.19; and at pH 6: 1.24 ± 0.00, corresponding to a Koc of 17.3. These results indicate a very high mobility in soil.
Executive summary:

The adsorption coefficient (Koc) of 2 -methyl-p-phenylenediamine sulfate, on soil and on sewage sludge, was determined using high performance liquid chromatography (HPLC) according to the OECD 121 Guideline.

The test was conducted at two different pH values with a nominal test substance concentration of 5 mg/L in a mobile phase of 55 % methanol and 45 % citrate-buffer (pH 6.0 and 3.0).

Samples of the test substance were analyzed threefold via HPLC on a cyanopropyl (CN-) column with UV - detection. Calibration was performed using six reference items with known values of log Koc (values from batch equilibrium experiments given in literature), each with a nominal concentration of 5 mg/L in mobile phase. Analysis of the reference items was performed once before and after analysis of test substance, respectively. Dead time of the HPLC-system was determined threefold using 5 mg/L sodium nitrate in mobile phase.

The log Koc for the test substance was:

at pH 3: 0.076 ± 0.010 (corresponding to a Koc of 1.19), and

at pH 6: 1.24 ± 0.00 (corresponding to a Koc of 17.3).

According to the McCall classification scheme of soil mobility potential, these results indicate the test substance would have a very high mobility in soil.

Endpoint:
adsorption / desorption
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Accepted calculation method.
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6
Reference:
Composition 0
Guideline:
other: REACH guidance on QSARs R.6 2008
Principles of method if other than guideline:
Calculation according to KOCWIN v2.00
Type of method:
other: Calculation according to KOCWIN v2.00
Test material information:
Composition 1
Type:
Koc
Value:
55.39
Remarks on result:
other: Koc Estimate from MCI (Molecular Connectivity Index, first-order)
Type:
Koc
Value:
5.062
Remarks on result:
other: Koc Estimate from Log Kow

Accuracy & Domain

Statistical Accuracy

Overall, the MCI methodology is somewhat more accurate than the Log Kow methodology, although both methods yield good results. If the Training dataset are combined in to one dataset of 516 compounds (69 having no corrections plus 447 with corrections), the MCI methodology has an r2, standard deviation and average deviation of 0.916, 0.330 and 0.263, respectively, versus 0.86, 0.429 and 0.321 for the Log Kow methodology.

Domain

Maximum and minimum number of istances for each correction factor are listed in appendix D of KOCWIN help menu.

Training Set Molecular Weights:

Minimum MW:  32.04

Maximum MW:  665.02

Average MW:  224.4

 

Validation Molecular Weights:

Minimum MW:  73.14

Maximum MW:  504.12

Average MW:  277.8

 

Currently there is no universally accepted definition of model domain.  However, users may wish to consider the possibility that log Koc estimates are less accurate for compounds outside the MW range of the training set compounds, and/or that have more instances of a given fragment than the maximum for all training set compounds.  It is also possible that a compound may have a functional group(s) or other structural features not represented in the training set, and for which no fragment coefficient or correction factor was developed.  These points should be taken into consideration when interpreting model results.

The test item fall within the domain of applicability both as molecular weight, number of instances and presence of structural features not represented in the training set, i.e. zero.

Conclusions:
Using EPI Suite 4.1, the Koc estimation of the test item 2-methyl-p-phenylenediamnine (CAS 95-70-5) , is of 55.39 L/kg (estimation based on MCI method) and of 5.062 l/kg based on Log Kow (-0.321, see Physical and chemical properties).

Description of key information

The adsorption coefficient (Koc) was determined on a structurally related substance: 2-Methyl-p-phenylenediamine sulfate. 2-Methyl-p-phenylenediamine sulfate (Haarbraun) Koc measured according to OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC)) was 0.076 at pH 3 and 17.3 at pH 6.

Key value for chemical safety assessment

Koc at 20 °C:
17.3

Additional information

The adsorption coefficient (Koc) was determined on a structurally related substance: 2-Methyl-p-phenylenediamine sulfate.

2-Methyl-p-phenylenediamine sulfate (Haarbraun) Koc was measured according to OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC)).

Dead time at pH 3= 3.067 +/- 0.013, at pH 6= 2.775 +/- 0.008, the validity critera were fullfilled.

According to the McCall classification scheme of soil mobility potential a Koc of 1.19 (pH 3) and of 17.3 (pH 6) would indicate a very high mobility for the test substance.

Using EPI Suite 4.1, the Koc estimation of the test item 2-methyl-p-phenylenediamine (CAS 95-70-5) is of 55.39 L/kg (estimation based on MCI method) and of 5.062 l/kg based on Log Kow (-0.321, see Physical and chemical properties).

These results fully support the Koc value of 17.3 measured on the structurally analogue 2-methyl-p-phenylenediamine sulfate at pH 6.