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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:
February 21 to 24, 2020
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))
GLP compliance:
yes (incl. QA statement)
Type of method:
HPLC estimation method
Specific details on test material used for the study:
Centella asiatica dry extract
Batch No. 972/43/A
Appearance dark green, powder
Retesting date: August 31, 2020
Storage: room temperature
Radiolabelling:
not specified
Test temperature:
25 °C
Details on study design: HPLC method:
Detector: 200 nm (for the reference items)
Column: LiChrospher 100 CN (5µm) 250-4, No.: 933278
Temperature: 25 °C
Mobile Phase: Acetonitrile : Water = 3 : 7 (v/v)
Flow Rate: 1 mL/min (for the reference items)
Injection Volume: 20 µL (2 µL for Acetanilide)

Test Solutions
The reference items were dissolved in acetonitrile. The concentrations of the stock solutions were about 1 mg/mL. These stock solutions were diluted with the mobile phase resulting in concentrations of approximately 10 µg/mL.

The test item was dissolved in acetonitrile. The concentration of the stock solution was about 1 mg/mL. This stock solution was diluted with the mobile phase resulting in concentration of approximately 10 µg/mL

Test Solutions
The reference items were dissolved in acetonitrile. The concentrations of the stock solutions were about 1 mg/mL. These stock solutions were diluted with the mobile phase resulting in concentrations of approximately 10 µg/mL.
The test item was dissolved in acetonitrile. The concentration of the stock solution was about 1 mg/mL. This stock solution was diluted with the mobile phase resulting in concentration of approximately 10 µg/mL.

Three series of the above-mentioned reference solutions were measured with two parallel injections, each. Three series of the test item solution were measured with two parallel injections, each. The retention times were determined. The three calibration series and three test item series were measured alternately.

For the determination of t0 (t0 = retention time of the unretarded component) three series of sodium nitrate solution were injected twice.

The pH of the mobile phase was 5.67.

Madecassicoside and Asiaticoside component of the test item was detected by MS, the Acetanilide reference item, as a first eluting standard was detected by UV and MS method, too. The difference of retention times was 0.023 min. The retention times of Madecassicoside and Asiaticoside component of the test item was corrected with this value.

Results Evaluation
The capacity factors, k were calculated from the retention times (tR) of the selected reference items and the dead time (t0):
Then the log k data of the reference items were plotted against their log Koc values given in Table 2.
The regression coefficients (a, b) were determined by linear regression calculation using the least squares method.
The log Koc value of a test item is calculated, using these regression coefficients and the capacity factor of the test item:
log k = a + b*log Koc

where:
Koc adsorption coefficient
a constant
b slope
k capacity factor

Type:
log Koc
Value:
< 1.25 dimensionless
Temp.:
25 °C
Details on results (HPLC method):
Retention times measured for Madecassicoside and Asiaticoside component of the test item (3.072 and 3.408 min) are lower than the retention time of the first eluting standard: Acetanilide (4.195 min). This result shows that log Koc of Madecassicoside and Asiaticoside component of the test item is lower than the calibrated range. As Acetanilide is the reference item with the lowest Koc value (OECD 121).
Validity criteria fulfilled:
yes
Conclusions:
Using the HPLC method the log Koc of Madecassicoside and Asiaticoside component of the test item was determined to be < 1.25.

Description of key information

Using the HPLC method the log Koc of Madecassicoside and Asiaticoside component of the test item was determined to be < 1.25.

Key value for chemical safety assessment

Koc at 20 °C:
17.78

Additional information

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