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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:
24-09-2001 to 24-01-2002
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:
equivalent or similar 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: February 2000; signature: April 2000
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 1100 series HPLC.
- Type: Phenosphere Next 5μ CN (150 x 4.6 mm id)
- Type, material and dimension of analytical (guard) column: None reported.
- Detection system: UV-diode array detection, 220 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. Adjusted to approximately neutral pH with 0.002 M sodium hydroxide
- Experiments with additives carried out on separate columns: No
- pH: mobile phase: pH = 7.1
- 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: 99.5%, as certified by supplier), 760 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 244 mg/L
- Identity: Atrazine, CAS 1912-24-9, Purity 99.2%, log Koc 1.81 (OECD Guideline 121); concentration 50.5 mg/L
- Identity: Isoproturon, CAS 34123-59-6, Purity 99.9%, log Koc 1.86 (OECD Guideline 121); concentration 111 mg/L
- Identity: Triadimenol, CAS 55219-65-3, Purity 99.2%, log Koc 2.40 (OECD Guideline 121); concentration 209 mg/L
- Identity: Linuron, CAS 330-55-2, Purity > or = 99.5%, log Koc 2.59 (OECD Guideline 121); concentration 107 mg/L
- Identity: Naphthalene, CAS 91-20-3, Purity 99%, log Koc 2.75 (OECD Guideline 121); concentration 53 mg/L
- Identity: Fenthion, CAS 55-38-9, Purity 98%, log Koc 3.31 (OECD Guideline 121); concentration 733 mg/L
- Identity: alpha-Endosulfan, CAS 959-98-8, Purity 99.8%, log Koc 4.09 (OECD Guideline 121); concentration 233 mg/L
- Identity: Diclofop-methyl, CAS 51338-27-3, Purity 99.9%, log Koc 4.20 (OECD Guideline 121); concentration 213 mg/L
- Identity: DDT, CAS 50-29-3, Purity 98%, log Koc 5.63 (OECD Guideline 121); concentration 220 mg/L

DETERMINATION OF RETENTION TIMES
- Quantity of test item introduced in the column: 10μL per injection for dead time and reference items and/or 10μL for test item; an aliquot of test item (2.0291 g) was diluted to 200 mL with methanol.
- 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 which cover both substances suitable for 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. 4.43 dimensionless
pH:
7.1
Temp.:
30 °C
Type:
Koc
Value:
ca. 26 800 L/kg
pH:
7.1
Temp.:
30 °C
Details on results (HPLC method):
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'.
- Retention times of reference substances used for calibration: Reference sample injections completed in duplicate.
- Identity: Acetanilide, Retention time average: 4.047 minutes
- Identity: Atrazine, Retention time average: 4.750 minutes
- Identity: Isoproturon, Retention time average: 5.106 minutes
- Identity: Triadimenol, Retention time average: 5.952 minutes
- Identity: Linuron, Retention time average: 6.276 minutes
- Identity: Naphthalene, Retention time average: 6.415 minutes
- Identity: Fenthion, Retention time average: 9.141 minutes
- Identity: alpha-Endosulfan, Retention time average: 11.507 minutes
- Identity: Diclofop-methyl, Retention time average: 11.169 minutes
- Identity: DDT, Retention time average: 22.051 minutes

- Dead-Time: 3.238 minutes
- Details of fitted regression line (log k' vs. log Koc): Linear regression of all reference substances; A = - 0.84 , B = 0.299 and R = 0.985
- Retention data for test item: Single peak. The average retention time; peak 1: 13.1 minutes (Log Koc = 4.43)
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 = 4.43 at 30°C and pH 7.1 by HPLC analysis.
Executive summary:

The study was performed to OECD TG 121 guideline under GLP to assess the adsorption coefficient (Koc) of the test item in accordance with GLP using a high-performance chromatography system. The retention times of the test item 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 approximately neutral pH (pH 7.1) 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. Under the conditions of this study, the test item adsorption coefficient (log Koc) for soil/sewage sludge was estimated to be log Koc 4.43 at 30°C and pH 7.1 by HPLC analysis.

Description of key information

log Koc = 4.43, 30 °C, pH 7.1 and 1 atm, OECD TG 121, 2002

Supporting information:

Log Koc, soil (main constituents): 4.39 at 25 °C; ca. pH 7, QSAR Prediction - KOCWIN v2.00, 2019

Key value for chemical safety assessment

Additional information

Key study: OECD TG 121, 2002 : The study was performed to OECD TG 121 guideline under GLP to assess the adsorption coefficient (Koc) of the test item in accordance with GLP using a high-performance chromatography system. The retention times of the test item 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 approximately neutral pH (pH 7.1) 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. Under the conditions of this study, the test item adsorption coefficient (log Koc) for soil/sewage sludge was estimated to be log Koc 4.43 at 30°C and pH 7.1 by HPLC analysis.

Supporting data: QSAR Predictions KOCWIN v2.00 model, 2019 :

Log Koc (main constituents): (1-ethoxyethoxy)cyclododecane : 4.39

Based on Log Kow regression from Log Kow = 6.60, extrapolated measured data (OECD TG 117, 2001).

 

Log Koc (all constituents) : < or = 4.39

Based on mixture of Log Kow measured data and estimates from the parallel KOWWIN v1.68 model.