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Environmental fate & pathways

Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
13 September 2012 to 12 December 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
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)
Type of method:
HPLC estimation method
Radiolabelling:
no
Details on study design: HPLC method:
As the test material was considered to not contain any test relevant dissociation constants, testing was carried out at approximately neutral pH with the test material in a non-ionised state.

EQUIPMENT
- Apparatus: Agilent Technologies 1100, incorporating autosampler and workstation
- Type: HPLC System (commercially available cyanopropyl reverse phase HPLC column containing lipophilic and polar moieties)
- Column: XSelect HSS CYANO 5 μm (150 x 4.6 mm id)
- Column temperature: 30 °C
- Flow-rate: 1.0 mL/min
- Injection volume: 10 μL
- Detection system: UV detector; wavelength (dead time and reference standards) 210 nm and (sample) 288 nm

MOBILE PHASES
- Type: Methanol:purified water (55:45 v/v)
- pH: 5.7
- Solutes for dissolving test and reference substances: The test material was diluted to 100 mL with methanol. Solutions of the reference materials were prepared in methanol.

DETERMINATION OF DEAD TIME
- Method: The dead time was determined by measuring the retention time of formamide [purity: 99.94 %, 666 mg/L solution in methanol:purified water (55:45 v/v)].

REFERENCE SUBSTANCES
- Identity: Phenol, atrazine, isoproturon, triadimenol, linuron, naphthalene, endosulfan-diol, fenthion, α-endosulfan, phenanthrene. diclofop-methyl and DDT.

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 0.1046 g
- Quantity of reference substances (mg/L): Phenol 114, atrazine 105, isoproturon 100, triadimenol 133, linuron 98, naphthalene 129, endosulfan-diol 116, fenthion 146, α-endosulfan 132, phenanthrene 134. diclofop-methyl 124 and DDT 157.

REPETITIONS
- Number of determinations: The sample, dead time and reference standard solutions were injected in duplicate.

EVALUATION
- Calculation of capacity factors k': The capacity factors (k') for the reference standards were calculated using the following equation:
k' = (tr –t0) / t0
where:
k' = capacity factor
tr = retention time (min)
t0 = dead time (min)
A correlation of log k' versus log Koc of the calibration standards was plotted using linear regression.

- Calculation of retention times: A calibration curve was constructed from the retention time data of the dead time and reference standard solutions.

- Determination of the log Koc value: The adsorption coefficient was calculated using the following equation:
Log10 Koc = (Log10k' – A) / B
where:
Koc= adsorption coefficient
k' = capacity factor
A = intercept of the calibration curve
B = slope of the calibration curve
Key result
Type:
Koc
Value:
71.3
Key result
Type:
log Koc
Value:
1.85
Details on results (HPLC method):
The mobility classification of the test material was obtained by comparing the calculated Koc value to the mobility classes according to McCall et al. 1981 as follows:
Range of Koc: 0 – 50: very high mobility; 50 – 150: high mobility; 150 – 500: medium mobility; 500 – 2000: low mobility; 2000 – 5000: slightly mobile; and > 5000: immobile.

The adsorption coefficient (Koc) of the test material was determined to be 71.3 (log10 Koc 1.85). This would indicate that the environmental mobility of the test material is high.


As the slope of the calibration curve for the reference standards showed good first order correlation and as the retention times between duplicate injections for each solution were consistent, the HPLC method was considered valid for the determination of adsorption coefficient. Based on the chromatographic data, the test material was considered to be stable during the test procedure.

Table 1: Adsorption Coefficient of the Sample

Injection

Retention Time (mins)

Capacity Factor (k')

Log10k'

Log10Koc

Mean Log10Koc

Adsorption Coefficient

1

3.712

3.710

0.981

-0.009

1.853

71.3

2

3.707

Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of this study, the adsorption coefficient (Koc) of the test material was determined to be 71.3, log10 Koc 1.85.
Executive summary:

The adsorption coefficient (Koc) of the test material was investigated using the HPLC screening method in accordance with the standardised guidelines EU Method C.19 and OECD 121 under GLP conditions.

The test utilised a high performance liquid chromatograph. A commercially available cyanopropyl reverse phase HPLC column containing lipophilic and polar moieties was used. As the test material was considered to not contain any test relevant dissociation constants, testing was carried out at approximately neutral pH with the test material in a non-ionised state.

To prepare the sample for the test, 0.1046 g of test material was diluted to 100 mL with methanol. The dead time was determined by measuring the retention time of formamide and solutions of appropriate reference standards were prepared in methanol. The sample, dead time and reference standard solutions were then injected in duplicate.

A calibration curve was constructed from the retention time data of the dead time and reference standard solutions and the capacity factors (k') for the reference standards were calculated. The capacity factor and adsorption coefficient of the test material were then determined.

As the slope of the calibration curve for the reference standards showed good first order correlation and as the retention times between duplicate injections for each solution were consistent, the HPLC method was considered valid for the determination of adsorption coefficient. Based on the chromatographic data, the test material was considered to be stable during the test procedure.

Under the conditions of this study, the adsorption coefficient (Koc) of the test material was determined to be 71.3, log10 Koc 1.85. This would indicate that the environmental mobility of the test material is high.

Description of key information

The adsorption coefficient (Koc) of the test material was determined to be 71.3, log10 Koc 1.85.

Key value for chemical safety assessment

Koc at 20 °C:
71.3

Additional information

The adsorption coefficient (Koc) of the test material was investigated using the HPLC screening method in accordance with the standardised guidelines EU Method C.19 and OECD 121 under GLP conditions. The study was assigned a reliability score of 1 in accordance with the criteria for assessing data quality set forth by Klimisch et al. (1997).

The test utilised a high performance liquid chromatograph. A commercially available cyanopropyl reverse phase HPLC column containing lipophilic and polar moieties was used. As the test material was considered to not contain any test relevant dissociation constants, testing was carried out at approximately neutral pH with the test material in a non-ionised state.

To prepare the sample for the test, 0.1046 g of test material was diluted to 100 mL with methanol. The dead time was determined by measuring the retention time of formamide and solutions of appropriate reference standards were prepared in methanol. The sample, dead time and reference standard solutions were then injected in duplicate.

A calibration curve was constructed from the retention time data of the dead time and reference standard solutions and the capacity factors (k') for the reference standards were calculated. The capacity factor and adsorption coefficient of the test material were then determined.

As the slope of the calibration curve for the reference standards showed good first order correlation and as the retention times between duplicate injections for each solution were consistent, the HPLC method was considered valid for the determination of adsorption coefficient. Based on the chromatographic data, the test material was considered to be stable during the test procedure.

Under the conditions of this study, the adsorption coefficient (Koc) of the test material was determined to be 71.3, log10 Koc 1.85. This would indicate that the environmental mobility of the test material is high.

[LogKoc: 1.85]