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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:
Experimental starting date: 11 August 2012. Experimental completion date: 10 October 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
Qualifier:
according to guideline
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
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. QA statement)
Type of method:
HPLC estimation method
Details on study design: HPLC method:
EQUIPMENT
- Apparatus: The test utilized a high performance liquid chromatograph. A commercially available cyanopropyl reverse phase HPLC column containing lipophilic and polar moieties was used.

MOBILE PHASES
- pH: As the test item contains no environmentally relevant dissociation constants, testing was carried at approximately neutral pH, with the test item in a unionized form.

DETERMINATION OF DEAD TIME
- The dead time was determined by measuring the retention time of formamide (purity: > 99.5 %, 646 mg/L solution in mobile phase).

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: Test item (0.1010 g) was diluted to 100 ml with methanol to give a concentration of 1.01 g/L.
- The sample, dead time and reference standard solutions were injected in duplicate using the following HPLC parameters:

HPLC System: Agilent Technologies 1100, incorporating autosampler and workstation
Column: Waters XSelect CN 5μm (150 x 4.6 mm id)
Column temperature: 30 ºC
Mobile phase: Methanol: purified water (55:45 v/v)
pH of mobile phase: 6.2
Flow-rate: 1.0 mL/min
Injection volume: 10 μL
UV detector wavelength: 210 nm

REPETITIONS
- Number of determinations: 2

DATA HANDLING
Construction of calibration curve
A calibration curve was constructed from the retention time data of the dead time and reference standard solutions. The capacity factors (k) for the reference standards were calculated using Equation 3.7.

Adsorption coefficient of sample
The capacity factor was calculated using Equation 3.7 and the log10 Koc value determined using Equation 3.8 with reference to the calibration curve.

Capacity factor
The capacity factor (k) was determined using the Equation 3.7

Equation 3.7: 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 is plotted using linear regression.

Adsorption Coefficient
The adsorption coefficient was calculated using Equation 3.8.

Equation 3.8: Log10Koc= (Log10 k- A)/ B

Where Koc = adsorption coefficient, k = capacity factor, A = intercept of the calibration curve, B = slope of the calibration curve
Type:
Koc
Value:
7.06 dimensionless
Temp.:
30 °C
Type:
log Koc
Value:
0.849 dimensionless
Temp.:
30 °C
Details on results (HPLC method):
- 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.
- Graph of regression line attached
Validity criteria fulfilled:
yes
Conclusions:
The adsorption coefficient of the test material was assessed according to OECD guideline 121 and determined to be 7.06, log10koc 0.849. This value indicates that the test item has very high environmental mobility.
Executive summary:

The adsorption coefficient was determined to be 7.06, log10Koc0.849, using the HPLC screening method, designed to be compatible with Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001. This value indicates that the test item has very high environmental mobility.

Description of key information

The adsorption coefficient of the test material was assessed according to OECD guideline 121 and determined to be 7.06, Log10 Koc 0.849. This value indicates that the test item has very high environmental mobility.

Key value for chemical safety assessment

Koc at 20 °C:
7.06

Additional information

The adsorption coefficient was determined to be 7.06, log10Koc 0.849, using the HPLC screening method, designed to be compatible with Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001. This value indicates that the test item has very high environmental mobility (based on the mobility classification 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)).

[LogKoc: 0.849]