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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
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
GLP compliance:
yes
Type of method:
HPLC estimation method
Media:
soil
Radiolabelling:
no
Test temperature:
40 °C
Details on study design: HPLC method:
INSTRUMENTATION:
- Liquid Chromatograph: HP 1090 with DAD-detector (Hewlett Packard, 40880 Ratingen, Germany)
- Column: Zorbax CN, 5 μm, length = 250 mm, i.d. = 4.6 mm (Bischoff, 71229 Leonberg, Germany)
- Injection volume: 250 μL*
- Flow rate: 1.5 mL/min
- Stationary phase: Commercial cyanopropyl chemically bound resins on a silica base
- Mobile phase: methanol / 0.01 M citrate-buffer pH 6.0 (55/45, v/v)
- Wave length: 210, 254 and 280 nm
- Run time: 15 min
* Because of a 10-fold concentrated solution the injection volume for the sodium nitrate solution, used for determination of the HPLC dead time, was
25 μL.

REFERENCE COMPOUNDS:
The reference compounds were provided by laboratories: Dr. Krohn and Dr. Schneider, Bayer AG, PF-E/FT-EA; Dr. Ehrenstorfer-Schäfers, Augsburg; Aldrich and Merck.

CHEMICALS AND REAGENTS:
- Methanol: Promochem, No. 3041 (46485 Wesel, Germany)
- Citrate buffer: Citric acid monohydrate (Merck, No. 1.00244.1000 adjusted to pH 6.0 with a water based solution of Sodium Hydroxide, Merck, No. 6498.1000)
- Water: purified in a Milli-Q unit

QUALITY CONTROL:
All analytical standards and standard solutions used in this study were kept in a refrigerator at all times when not in use.
Details on matrix:
Commercial cyanopropyl chemically bound resins on a silica base was used.
Details on test conditions:
STOCK SOUTION OF TEST SUBSTANCE:
An amount of 12.43 mg was weighed into a 10-mL volumetric flask and diluted to volume with methanol.

STOCK SOUTION OF REFERENCE SUBSTANCE:
An amount of approx. 10 mg was weighed into separate 10-mL volumetric flasks and diluted to volume with methanol.

STANDARD SOLUTIONS:
The measurements were carried out at concentrations of approx. 5 mg/L. The solvent was similar to the mobile phase of the HPLC method (i.e. methanol / 0.01 M citrate buffer pH 6.0, 55/45, v/v). A total of 0.1 mL taken from each standard stock solution was transferred into a 20-mL volumetric flasks and diluted to volume with the mobile phase methanol / citrate buffer pH 6.0. The flasks were shaken and ultrasonicated for one minute to dissolve the substance. From the sodium nitrate stock solution a total of 1 mL was transferred into a 20-mL volumetric flasks and diluted to volume with the mobile
phase methanol / citrate buffer pH 6.0 to reach a concentration of approx. 50 mg/L.
Key result
Type:
Koc
Value:
80.4 dimensionless
pH:
6
Temp.:
40 °C
Matrix:
commercially available cyanopropyl solid phase containing lipophilic and polar moieties
Statistics:
Calculations were performed using the computer software EXCEL (OFFICE 97®, Microsoft). The results given are values rounded to one or two digits. Rounding
errors may occur if recalculations are made using the rounded figures.
Validity criteria fulfilled:
not specified
Conclusions:
The estimated Koc value of the test substance is 80.4.
Executive summary:

The adsorption coefficient Koc on soil was estimated using the High Performance Liquid Chromatography (HPLC) based method which is outlined in OECD test guideline 121. Commercial cyanopropyl chemically bound resins on a silica base was used. As mobile phase methanol/0.01 M citrate-buffer pH 6.0 (55/45, v/v) was used.

Twelve reference standards of known Koc from batch equilibrium experiments were chromatographed using a CN-based on a HPLC method to determine an average capacity factor k’. Sodium nitrate was used to determine the HPLC system dead time (t0). A regression line was plotted against the determined k’ values and the known Koc values (log k’ vs. log Koc) of the reference standards. The test substance was chromatographed during the same sample sequence as the reference substances, and the average k’ value was determined. The Koc value was estimated by interpolation from the reference substance regression line. The linear regression of measured k’ values against literature Koc values yielded a correlation coefficient R² of 0.885. The estimated Koc value for the test substance is 80.4.

Description of key information

The adsorption coefficient Koc on soil was estimated using the High Performance Liquid Chromatography (HPLC) based method which is outlined in OECD test guideline 121. Commercial cyanopropyl chemically bound resins on a silica base was used. As mobile phase methanol/0.01 M citrate-buffer pH 6.0 (55/45, v/v) was used.

Twelve reference standards of known Koc from batch equilibrium experiments were chromatographed using a CN-based on a HPLC method to determine an average capacity factor k’. Sodium nitrate was used to determine the HPLC system dead time (t0). A regression line was plotted against the determined k’ values and the known Koc values (log k’ vs. log Koc) of the reference standards. The test substance was chromatographed during the same sample sequence as the reference substances, and the average k’ value was determined. The Koc value was estimated by interpolation from the reference substance regression line. The linear regression of measured k’ values against literature Koc values yielded a correlation coefficient R² of 0.885. The estimated Koc value for the test substance is 80.4.

Key value for chemical safety assessment

Koc at 20 °C:
80.4

Additional information

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