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Adsorption / desorption

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Endpoint:
adsorption / desorption: screening
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
key study
Study period:
September 2010
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Result is the output from a well-known estimation model for environmental distribution factors. The result was calculated on the basis of reliable test data (experimentally-derived log Pow).
Qualifier:
no guideline followed
Principles of method if other than guideline:
In the absence of suitable testing data, the Adsorbtion / Desorption Coefficient was estimated using a computer model, based on the structure, and information on the log Kow, boiling point, water solubility, and vapour pressure. The computer model used was EPIWeb, and the calculation of Koc was performed by KOCWIN version 2.00.
Type:
log Koc
Value:
1.473
Remarks on result:
other: Value calculated using the Kow method.
Type:
log Koc
Value:
2.71
Remarks on result:
other: Value calculated using the Molecular Connectivity Index (MCI) method
Conclusions:
The calculated log Koc, derived on the basis of the experimentally determined log Kow (log Kow = 0.78) was 1.473.
Executive summary:

An environmental modelling program, EPIWeb, was used to estimate the Adsorbtion / Desorption coefficient. The CAS number was used to identify the substance and to recover the SMILES notation and estimate the molecular weight; a number of measured physico-chemical parameters (log Kow, Boiling point, Vapour pressure, and water solubility).

The calculated log Koc value based on the log Kow was found to be 1.473; the value calculated on the basis of the MCI (Molecular Connectivity Index) method was 2.710.

The value calculated on the basis of the log Kow method was considered slightly more reliable as it was based on an experimentally-derived value; this is the value which will be reported.

Endpoint:
adsorption / desorption: screening
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
supporting study
Study period:
12 November 1999 to 10 January 2000
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
GLP study performed in accordance to OECD test guideline, however the experimental estimation could not be performed as no suitable HPLC method could be established. A subsequent structure-based estimation gave too wide a margin for error for the result to be considered reliable.
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
Principles of method if other than guideline:
Deviations: As a result of the chemical nature of 1,3-BAC, the adsorption coefficient could not be measured using the procedure specified in the OECD draft document (Dec 1998). Therefore, using a 'Molecular Topology/Fragment Contribution Method For Predicting Soil Sorption Coefficients', the log10Koc of 1,3-BAC was calculated .
GLP compliance:
yes (incl. certificate)
Type of method:
HPLC estimation method
Media:
soil/sewage sludge
Test temperature:
HPLC system:
Column temperature: 30°C
Mobile phase: methanol:water (55:45 v/v)
pH of mobile phase: 6.0
Flow rate: 1ml/min
UV detector wavelength: 210 nm
Injection volume: 10µl

GC system:
Oven temperature program: initial 105 ºC for 1 minute, rate 16 ºC/minute, final 210 ºC for 5 minutes
Injection temperature: 250 ºC
Nitrogen-phosphorus detector temperature: 300ºC
Injection volume: 1 µl
Retention time: ca 7 mins


Details on study design: HPLC method:
EQUIPMENT
- Apparatus: HPLC System: Hewlett-Packard 1050, incorporating autosampler and workstation
- Type, material and dimension of analytical (guard) column: Column: Nucleosil 5µ CN (250 mmx4.6 mm id)
- Detection system: GC: Hewlett-packard 5890A, incorporating autosampler and workstation


MOBILE PHASES
- Type: methanol:water (55:45 v/v)
- Experiments with additives carried out on separate columns: no
- pH: 6.0
- Solutes for dissolving test and reference substances: methanol and formamide, respectively


DETERMINATION OF DEAD TIME
- Method: by means of homologous series

REFERENCE SUBSTANCES
- Identity: formamide, acetanilide, phenol, atrazine, isoproturon, triadimenol, linuron, naphthalene, fenthion, alpha endosulfan, phenanthrene, diclofop-methyl, DDT


DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 10 µl
- Quantity of reference substances: 10 µl


REPETITIONS
- Number of determinations: 2 for each reference stubstance


EVALUATION
- Calculation of capacity factors k': k= tr – t0 / t0
- Determination of the log Koc value: PCKOCWIN
Details on test conditions:
Test material (0.1240g) was diluted to 50.0 ml with methanol.
Type:
log Koc
Value:
ca. 3
Details on results (HPLC method):
- Retention times of reference substances used for calibration:
Formamide: 3.798; acetanilide: 4.469; phenol: 4.405; atrazine:4.776; isoproturon: 5.161; triadimenol:5.442; linuron:5.854; naphthalene:6.328; fenthion:7.590; alpha endosulfan:7.458; phenanthrene:8.705; diclofop-methyl: 8.550; DDT:11.980
- Details of fitted regression line (log k' vs. log Koc): -0.999x + 0.259y=0 (r=0.966)
Transformation products:
not measured

Since the adsorption coefficient could not be measured using the technique specified in the study protocol, the log10Koc was estimated from the chemical structure. The chemical structure was entered directly into PCKOCWIN Version 1.66, software produced by the Syracuse Research Corportation. This software incorporates the ‘Molecular Topology/Fragment Contribution Method for Predicting Soil Sorptoin Coefficients’, W Melyan, P H Howard and R S Boethling, Environ. Sci. Technol. 26: 1560-7 (1992). The calculated value for log10Koc was 3.0. The calculation was validated and an estimate of the accuracy obtained by entering into PCKOCWIN the structures for a series of reference compounds, selected because they contain functional groups found in 1,3-BAC; the estimated accuracy was +/- 1.0 log units.

Validity criteria fulfilled:
no
Remarks:
Experimental determination as described in the OECD test guideline was not possible. Subsequently a computer model was used instead.
Conclusions:
As a result of the chemical nature of 1,3-BAC, the adsorption coefficient could not be measured. Therefore using a molecular topology/fragment contribution method for predicting soil sorption coefficients, the log10Koc of 1,3-BAC was calculated to be 3.0 +/- 1.0.
Executive summary:

As a result of the chemical nature of 1,3-BAC, the adsorption coefficient could not be measured using the procedure specified in the OECD draft document (December 1998): Estimation of the Adsorption Coefficient (Koc) on Soil and Sewage Sludge using High Performance Liquid Chromatography (HPLC), as no suitable detection method could be found. Using a 'Molecular Topology/Fragment Contribution Method For Predicting Soil Sorption Coefficients', the log10Kocof 1,3-BAC was calculated to be 3.0 ± 1.0.

Description of key information

Log10 Koc of 1,3-BAC was estimated by calculation to be 1.473. The respective Koc value is 29.7 L/kg.

Key value for chemical safety assessment

Koc at 20 °C:
29.7

Additional information

An environmental modelling program, EPIWeb, was used to estimate the Adsorbtion / Desorption coefficient. The CAS number was used to identify the substance and to recover the SMILES notation and estimate the molecular weight; a number of measured physico-chemical parameters (log10 Kow, Boiling point, Vapour pressure, and water solubility).

The calculated log10 Kocvalue based on the log10 Kowwas found to be 1.473; the value calculated on the basis of the MCI (Molecular Connectivity Index) method was 2.710.

The value calculated on the basis of the log10 Kowmethod was considered slightly more reliable as it was based on an experimentally-derived value; this is the value which will be reported.

In a study intended to measure the Koc (Safepharm, 2000), it was noted that as a result of the chemical nature of 1,3-BAC, the adsorption coefficient could not be measured using the procedure specified in the OECD draft document (December 1998): Estimation of the Adsorption Coefficient (Koc) on Soil and Sewage Sludge using High Performance Liquid Chromatography (HPLC), as no suitable detection method could be found. Using a 'Molecular Topology/Fragment Contribution Method For Predicting Soil Sorption Coefficients', the log10 Koc of 1,3-BAC was calculated to be 3.0 ± 1.0. The EPIWeb estimation was run in response to the result for the estimation in the 2000 study; it was considered that an error margin of ±1.0 was too wide for the calculated log10 Koc value to be considered reliable; on this basis, the EPIWeb result was used for calculations in environmental modelling.