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Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study performed under GLP. All relevant validity criteria were met.
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:
no
Qualifier:
according to
Guideline:
EU Method C.19 (Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge Using High Performance Liquid Chromatography (HPLC))
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
inspected: July 2016; signature: October 2016
Type of method:
HPLC estimation method
Media:
soil/sewage sludge
Radiolabelling:
no
Test temperature:
30 °C
Details on study design: HPLC method:
EQUIPMENT
- Apparatus: Agilent Technologies 1200 series HPLC.
- Type: XSelect HSS Cyano 5μ (150 x 4.6 mm id)
- Type, material and dimension of analytical (guard) column: None reported.
- Detection system: UV-diode array detection, 210 nm for the test item sample solution, 210 nm for the reference item and deadtime solutions

MOBILE PHASES
- Type: Methanol : purified water (55:45 v/v) Flow Rate 1mL per minute.
- Experiments with additives carried out on separate columns: No
- pH: mobile phase: pH = 6.4
- Solutes for dissolving test and reference substances: None.

DETERMINATION OF DEAD TIME
- Method: The dead time was determined by measuring the retention time of formamide (purity: 99.9%, as certified by supplier), 650 mg/L solution in methanol:purified water (55:45 v/v). Determined in duplicate.

REFERENCE SUBSTANCES
- Identity: Acetanilide, CAS 103-84-4, Purity 99%+, log Koc 1.25 (OECD Guideline 121); concentration 117 mg/L
- Identity: Atrazine, CAS 1912-24-9, Purity 99.1%, log Koc 1.81 (OECD Guideline 121); concentration 92 mg/L
- Identity: Isoproturon, CAS 34123-59-6, Purity >98.0%, log Koc 1.86 (OECD Guideline 121); concentration 106mg/L
- Identity: Triadimenol, CAS 55219-65-3, Purity 98.0%, log Koc 2.40 (OECD Guideline 121); concentration 105 mg/L
- Identity: Linuron, CAS 330-55-2, Purity 99.7%, log Koc 2.59 (OECD Guideline 121); concentration 104 mg/L
- Identity: Naphthalene, CAS 91-20-3, Purity 99%, log Koc 2.75 (OECD Guideline 121); concentration 103 mg/L
- Identity: Endosulfan-diol, CAS 2157-19-9, Purity 99.9%, log Koc 3.02 (OECD Guideline 121); concentration 108 mg/L
- Identity: Fenthion, CAS 55-38-9, Purity 97.9%, log Koc 3.31 (OECD Guideline 121); concentration 131 mg/L
- Identity: alpha-Endosulfan, CAS 959-98-8, Purity 99.6%, log Koc 4.09 (OECD Guideline 121); concentration 110 mg/L
- Identity: Phenanthrene, CAS 85-01-8, Purity > or = 99.5%, log Koc 4.09 (OECD Guideline 121); concentration 113 mg/L
- Identity: Diclofop-methyl, CAS 51338-27-3, Purity 99.1%, log Koc 4.20 (OECD Guideline 121); concentration 115 mg/L
- Identity: DDT, CAS 50-29-3, Purity 98.7%, log Koc 5.63 (OECD Guideline 121); concentration 102 mg/L

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 10μL per injection; an aliquot of test item (0.1025 g) was diluted to 10 mL with methanol to give a concentration of 10.3 g/L.
- Quantity of reference substances: 10μL per injection; the concentration of each reference substance is indicated above injected in duplicate.
- Intervals of calibration: The calibration was performed once specific for the study; with a range of log Koc suitable for the test item estimation of adsorption to sewage sludge and soil under OECD TG 121 guideline.

REPETITIONS
- Number of determinations: Two.

EVALUATION
- Calculation of capacity factors k': Calculated as a ratio of retention time of retained compounds relative to unretained substances after determination of the column dead time.
- Calculation of retention times: Determined empirically relative to the known column dead time.
- Determination of the log Koc value: Capacity factors (log k') for reference substances were plotted against absorption coefficients (log Koc). The log Koc for the test item was then calculated using the resultant equation for the calibration curve and the experimentally determined log k'.
Type:
log Koc
Value:
ca. 3.36
pH:
6.4
Temp.:
30 °C
Type:
Koc
Value:
ca. 2 270 L/kg
pH:
6.4
Temp.:
30 °C
Details on results (HPLC method):
- Calculation of capacity factors k': Calculated as a ratio of retention time of retained compounds relative to unretained substances after determination of the column dead time.
- Calculation of retention times: Determined empirically relative to the known column dead time.
- Determination of the log Koc value: Capacity factors (log k') for reference substances were plotted against absorption coefficients (log Koc). The log Koc for the test item was then calculated using the resultant equation for the calibration curve and the experimentally determined log k'.
- Retention times of reference substances used for calibration: Reference sample injections completed in duplicate.
- Identity: Acetanilide, Retention time average: 2.664 minutes
- Identity: Atrazine, Retention time average: 3.686 minutes
- Identity: Isoproturon, Retention time average: 3.954 minutes
- Identity: Triadimenol, Retention time average: 5.380 minutes
- Identity: Linuron, Retention time average: 5.545 minutes
- Identity: Naphthalene, Retention time average: 5.493 minutes
- Identity: Endosulfan-diol, Retention time average: 6.944 minutes
- Identity: Fenthion, Retention time average: 8.286 minutes
- Identity: alpha-Endosulfan, Retention time average: 11.866 minutes
- Identity: Diclofop-methyl, Retention time average: 12.800 minutes
- Identity: Phenanthrene, Retention time average: 9.026 minutes
- Identity: DDT, Retention time average: 25.604 minutes

- Dead-Time: 1.937 minutes
- Details of fitted regression line (log k' vs. log Koc): Linear regression of all reference substances; y = 0.3175x - 0.6234 , correlation coefficient (R2 = 0.9716)
- Retention data for test substance: Single peak (main constituents). The average retention time; peak 6: 7.297 minutes (Log Koc = 3.36)
For further information see table 1.
Validity criteria fulfilled:
yes
Conclusions:
The test item adsorption coefficient (log Koc) for soil/sewage sludge according to OECD Guideline 121 was estimated to be log Koc = 3.36 for three constituents at 30°C by HPLC analysis.
Executive summary:

The study was performed to OECD TG 121 and EU Method C.19 to assess the adsorption coefficient (Koc) of the test substance in accordance with GLP using a high performance chromatography system. The retention times of the test substance and selected reference items were accurately measured using HPLC fitted with a cyanopropyl column. The retention times were consistent over the course of the study. The dead time of the instrument was also measured and capacity factors were calculated for each substance. Calibration curves were constructed by plotting the capacity factor (log k') for the reference substances against their adsorption coefficients (log Koc). Linear regression analysis was performed and this showed a reasonable relationship between the capacity factors and the adsorption coefficients. The test was performed at a singular pH 6.4 as the test item does not possess ionisable moieties in an environmentally relevant pH range. The adsorption coefficient of the test item was estimated using the calibration curve constructed from all reference items. Due to the ability of the cyano column the three constituents were not resolved but elute as one peak. Under the conditions of this study, the test substance adsorption coefficient (log Koc) for soil/sewage sludge was estimated to be log Koc 3.36 for three constituents at 30°C and pH 6.4 by HPLC analysis.

Description of key information

log Koc = 3.36 (Koc 2270 L/kg), 30 °C, pH 6.4 and 1 atm, OECD TG 121, 2017

Key value for chemical safety assessment

Koc at 20 °C:
3.36

Additional information

Key study: OECD TG 121, 2017 : The study was performed to OECD TG 121 and EU Method C.19 to assess the adsorption coefficient (Koc) of the test substance in accordance with GLP using a high performance chromatography system. The retention times of the test substance and selected reference items were accurately measured using HPLC fitted with a cyanopropyl column. The retention times were consistent over the course of the study. The dead time of the instrument was also measured and capacity factors were calculated for each substance. Calibration curves were constructed by plotting the capacity factor (log k') for the reference substances against their adsorption coefficients (log Koc). Linear regression analysis was performed and this showed a reasonable relationship between the capacity factors and the adsorption coefficients. The test was performed at a singular pH 6.4 as the test item does not possess ionisable moieties in an environmentally relevant pH range. The adsorption coefficient of the test item was estimated using the calibration curve constructed from all reference items. Due to the ability of the cyano column the three constituents were not resolved but elute as one peak. Under the conditions of this study, the test substance adsorption coefficient (log Koc) for soil/sewage sludge was estimated to be log Koc 3.36 for three constituents at 30°C and pH 6.4 by HPLC analysis.