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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:
The study was conducted between 29 November 2016 and 30 November 2016
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
Media:
soil/sewage sludge
Radiolabelling:
no
Test temperature:
30 ºC
Details on study design: HPLC method:
HPLC System : Agilent Technologies 1200 Series, incorporating autosampler and workstation
Detector type : Ultraviolet (UV)
Column : Waters XSelect HSS Cyano 5 μm (150 x 4.6 mm id)
Column temperature : 30 ºC
Mobile phase : Methanol: purified water (55:45 v/v)
pH of mobile phase : 6.7
Flow-rate : 1.0 mL/min
Injection volume : 10 μL
UV detector wavelength : dead time and reference standards: 210 nm
sample: 241 nm
Analytical monitoring:
not specified
Details on test conditions:
Preparation of sample solution
Test item (0.0995 g) was diluted to 100 mL with methanol to give a concentration of 995 mg/L.

Preparation of dead time solution
The dead time was determined by measuring the retention time of formamide (purity* 99.94%, 633 mg/L solution in methanol: purified water (55:45 v/v)).

Preparation of reference standard solutions
Solutions of reference standards (see following table) were prepared in methanol.

Standard Purity (%)* Concentration (mg/L)
Acetanilide 99+ 109
Phenol 99.9 136
Atrazine 99.1 102
Isoproturon >98.0 114
Triadimenol 98.0 107
Linuron 99.7 104
Naphthalene 99 124
Endosulfan-diol 99.9 108
Fenthion 97.9 102
α-Endosulfan 99.6 109
Phenanthrene ≥99.5 105
Diclofop-methyl 99.1 104
DDT 98.7 106
Computational methods:
A calibration curve was constructed from the retention time data of the dead time and reference standard solutions.

The mobility classification of the test item was obtained by comparing the calculated Koc value to the mobility classes according to P.J. McCall, R.L. Swann, D.A. Laskowski, S.M. Unger, S.A. Vrona and H.J. Dishburger “Estimation of Chemical Mobility in Soil from Liquid Chromatography Retention Times”; Bull. Environm. Contam. Toxicol. 24, 190-195 (1980).

Range of Koc Mobility class
0 – 50 Very high
50 – 150 High
150 – 500 Medium
500 – 2000 Low
2000 – 5000 Slightly
> 5000 Immobile
Key result
Type:
log Koc
Value:
4.87 dimensionless
Temp.:
30 °C
Type:
other: Adsoprtion coefficient
Value:
74 800 dimensionless
Temp.:
30 °C
Details on results (HPLC method):
The retention times, capacity factor and log10 Koc value determined for the sample are shown in the following table:

Injection Retention time (mins) Capacity factor (k') Log10 k' Log10 Koc Mean log10 Koc Adsorption Coefficient
1 19.762 9.30 0.968 4.87 4.87 7.48 x 104
2 19.747 9.29 0.968 4.87


Overall log10 Koc: 4.87
Adsorption coefficient: 7.48 x 104

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 was consistent, the HPLC method was considered valid for the determination of adsorption coefficient. Based on the chromatographic data, the test item was considered to be stable during the test procedure.
Validity criteria fulfilled:
not specified
Conclusions:
The adsorption coefficient (Koc) of the test item has been determined to be 7.48 x 104, log10 Koc 4.87. This value indicates that the test item is immobile.
Executive summary:

The adsorption coefficient of GL500 has been determined to be 7.48 x 104, log10Koc 4.87, using the HPLC screening method, designed to be compatible with Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001 and Method C.19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008.

Description of key information

The adsorption coefficient (Koc) of the test item has been determined to be 7.48 x 104, log10Koc 4.87. This value indicates that the test item is immobile.

Key value for chemical safety assessment

Koc at 20 °C:
74 800

Additional information

[LogKoc: 4.87]