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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:
26-02-2014 to 26-01-2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study performed under GLP. All relevant validity criteria were met with acceptable deviations.
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:
Variation of the temperature was more than ± 1°C. The analytical column could not be placed in the column oven due to its length. No impact on retention times of reference or test items during the course of measurements. Was not a significant deviation.
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:
yes
Remarks:
see above
GLP compliance:
yes (incl. certificate)
Remarks:
inspected: July 2016; signature: January 2017
Type of method:
HPLC estimation method
Media:
other: soil and sediment
Radiolabelling:
no
Test temperature:
Column temperature: 20-25°C (Actual 21. 4 – 24.2 °C with mean = 22.9 °C ; During the course of measurements, the variation of the temperature was more than ± 1°C because the analytical column could not be placed in the column oven due to its length. There was no impact on retention times of reference or test items during the course of measurements. From calibration before and after test item injections).
Details on study design: HPLC method:
EQUIPMENT
- Instrument: UPLC Acquity
- Detector: Diode Array Detector (DAD) and Mass Spectrometry (MS) (for test item analyte identification)
- Column: YMC-Pack Cyano, 250 x 4.0 mm, S-5 IJm, 12nm, batch 11334
- Detection system: UV-diode array detection, 210 nm for the test item sample solution, 210 to 250 nm (range) for the reference items and 210 nm deadtime solutions ; for the test item MS-MS was utilised in MRM Electrospray positive mode.

MOBILE PHASES
- Type: Methanol: HPLC water (55 : 45 v/v); Flow-rate 0.8 mL per minute.
- Experiments with additives carried out on separate columns: No
- pH: mobile phase: pH = ca. 7.0
- Column temperature: 20-25°C (Actual 21. 4 – 24.2 °C with mean = 22.9 °C ; During the course of measurements, the variation of the temperature was more than ± 1°C because the analytical column could not be placed in the column oven due to its length. There was no impact on retention times of reference or test items during the course of measurements).
- Solutes for dissolving test and reference substances: None.

DETERMINATION OF DEAD TIME
- Method: by inert substance (e.g. Sodium Nitrate) which are not retained by the column

REFERENCE SUBSTANCES
Acetanilide, CAS 103-84-4, log Koc (soil) 1.26, log Koc (sewage sludge) 1.52 (OECD Guideline 121); concentration 5 mg/L
Atrazine, CAS 1912-24-9, log Koc (soil) 1.81, log Koc (sewage sludge) 1.66 (OECD Guideline 121); concentration 5 mg/L
Monuron, CAS 150-68-5, log Koc (soil) 1.99, log Koc (sewage sludge) 1.46 (OECD Guideline 121); concentration 5 mg/L
Linuron, CAS 330-55-2, log Koc (soil) 2.59, log Koc (sewage sludge) 2.43 (OECD Guideline 121); concentration 5 mg/L
Phenyl benzoate, CAS 93-99-2, log Koc (soil) 2.87, log Koc (sewage sludge) 3.26 (OECD Guideline 121); concentration 5 mg/L
Fenthion, CAS 55-38-9, log Koc (soil) 3.31, log Koc (sewage sludge) 3.75 (OECD Guideline 121); concentration 5 mg/L
Phenanthrene, CAS 85-01-8, log Koc (soil) 4.09, log Koc (sewage sludge) 4.35 (OECD Guideline 121); concentration 5 mg/L
4,4’-DDT, CAS 50-29-3, log Koc (soil) 5.63, log Koc (sewage sludge) - (OECD Guideline 121); concentration 20mg/L

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 7.5 μL per injection; an aliquot of test item (5000 mg/L) was diluted to with methanol and then a test concentration of 2750 mg/L (DAD) and 5 mg/L (MS analysis) test samples were prepared using methanol/HPLC water to mobile phase ratio (methanol/HPLC water 55:45 v/v). Injected in triplicate,
- Quantity of reference substances: 7.5 μL per injection; the concentration of each reference substance is indicated above injected in duplicate. One before and one after the test item injection. Dead time was determined at 5 mg/L in triplicate.

REPETITIONS
- Number of determinations: three

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
Remarks:
in soil
Value:
3.4 dimensionless
pH:
7
Temp.:
22.9 °C
Remarks on result:
other: Mean temperature: 22.9 °C
Type:
log Koc
Remarks:
in sewage sludge
Value:
3.7 dimensionless
pH:
7
Temp.:
22.9 °C
Remarks on result:
other: Mean temperature: 22.9 °C
Details on results (HPLC method):
- Retention times of reference substances used for calibration: See table 1.
- Details of fitted regression line (log k' vs. log Koc):
Soil: Calibration 1: r = 0.9834 and r2 = 0.9670 and Calibration 2: r = 0.9832 and r2 = 0.9666
Sewage sludge: Calibration 1: r = 0.9669 and r2 = 0.9348 and Calibration 2: r = 0.9662 and r2 = 0.9336
- Average retention data for test substance: See table 2

Table 1. Capacity Factors (k’) of the reference substances and for soil and sewage sludge

Reference Item

Log Koc Soil

Log Koc sewage sludge

1st calibration

2nd calibration

 

 

 

tr1 / min

k'

log k’

tr2 / min

k'

log k’

Acetanilide

1.26

1.52

3.779

1.45

0.161

3.797

1.46

0.164

Atrazine

1.81

1.66

4.303

1.79

0.253

4.314

1.79

0.253

Monuron

1.99

1.46

4.548

1.94

0.288

4.529

1.93

0.286

Linuron (1)

2.59

2.43

6.540

3.23

0.509

6.529

3.23

0.509

Benzoic acid phenyl ester

2.87

3.26

6.578

3.26

0.513

6.537

3.23

0.509

Fenthion

3.31

3.75

10.144

5.57

0.746

10.131

5.56

0.745

Phenanthrene

4.09

4.35

10.008

5.48

0.739

9.897

5.41

0.733

4,4’-DDT

5.63

-

22.575

13.6

1.130

22.697

13.7

1.14

 

 

 

 

 

 

 

 

 

tr1 = Retention time injection 1

tr2 = Retention time injection 2

k’ = Capacity Factor

Koc = Adsorption Coefficient

(1) = not used for tr sewage sludge determination

 

Table 2. Capacity Factors (k’) of the test item for soil and sewage sludge

 

Log Koc Soil

Log Koc sewage sludge

tr / min

k'

log k’

Test Item

 

 

8.485

4.492

0.6524

Peak 6

 

 

8.499

4.501

0.6533

 

 

 

8.523

4.517

0.6549

 

 

 

 

 

 

Mean

3.4 ± 0.1

3.4 ± 0.1

8.502

4.503

0.6535

95% C.I.

3.2 to 3.7

3.2 to 3.7

 

 

 

 

 

 

 

 

 

tr = Retention time

C.I. = Confidence Interval

 

Eight peaks in total were considered for data evaluation. Peak 6 was considered to be the test item, the major constituent, based on a combination of the DAD and MS/MS-detection.

Validity criteria fulfilled:
yes
Conclusions:
The test item adsorption coefficient (log Koc) according to OECD Guideline 121 was estimated by HPLC analysis to be for soil: log Koc 3.4 at 22.9 °C and for sewage sludge Koc = 3.7 at 22.9 °C.
Executive summary:

The study was performed to OECD TG 121 and EU Method C.19 to assess the adsorption coefficient (Koc) of the test item in accordance with GLP using an ultra performance chromatography system. The retention times of the test item and selected reference items were accurately measured using UPLC fitted with a cyanopropyl column with DAD and MS detection systems. 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 items against their adsorption coefficients (log Koc) prior to and post- test item injection. 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 ca. 7. The adsorption coefficient of the test item was estimated using the calibration curve constructed from all reference items and there were no significant differences in calibration 1 and calibration 2 and the calculated adsorption coefficient. The main constituent(s) of the test item were identified using MS detection. Under the conditions of this study, the test item adsorption coefficient (log Koc) for soil/sewage sludge was estimated to be for soil: log Koc 3.4 and for sewage sludge Koc = 3.7 at 22.9 °C and pH ca. 7.0.

Description of key information

log Koc (soil) = 3.4 (Koc 2512 L/kg), 22.9 °C, ca. pH 7 and 1 atm, OECD TG 121, 2017

log Koc (sewage sludge) = 3.7 (Koc 5012 L/kg), 22.9 °C, ca. pH 7 and 1 atm, OECD TG 121, 2017

Key value for chemical safety assessment

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 item in accordance with GLP using an ultra performance chromatography system. The retention times of the test item and selected reference items were accurately measured using UPLC fitted with a cyanopropyl column with DAD and MS detection systems. 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 items against their adsorption coefficients (log Koc) prior to and post- test item injection. 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 ca. 7. The adsorption coefficient of the test item was estimated using the calibration curve constructed from all reference items and there were no significant differences in calibration 1 and calibration 2 and the calculated adsorption coefficient. The main constituent(s) of the test item were identified using MS detection. Under the conditions of this study, the test item adsorption coefficient (log Koc) for soil/sewage sludge was estimated to be for soil: log Koc 3.4 and for sewage sludge Koc = 3.7 at 22.9 °C and pH ca. 7.0.