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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
30.1.2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
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
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
GLP compliance:
yes
Type of method:
HPLC estimation method
Media:
soil/sewage sludge
Radiolabelling:
no
Test temperature:
25 °C
Details on study design: HPLC method:
EQUIPMENT
- Apparatus: Liquid chromatograph
- Type: Shimadzu LC20 Nexera
- Type, material and dimension of analytical (guard) column: Eclipse XDB-CN, 150 x 4.6 mm, 5 µm
- Detection system: UV/VIS (210 nm NaNO3; 240 nm test and reference substances)

MOBILE PHASES
- Type: 55 % ACN + 45 % citrate buffer (flow rate 1.0 mL/minute)
- Experiments with additives carried out on separate columns: no
- pH: 6.5
- Solutes for dissolving test and reference substances: methanol

DETERMINATION OF DEAD TIME
- Method: by inert substances which are not retained by the column

REFERENCE SUBSTANCES
- Identity and purity: 2,5-Dichloroaniline 99 %, Benzamide ≥99 %, Aniline ≥99.5 %, Atrazine 98.8 %, Linuron 99.9 %, Phenanthrene ≥97 and Phenyl benzoate ≥98 %

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: Test substance solution was prepared by weighing 13.90 mg into a 50 mL volumetric flask and dissolving in methanol. A 5 mL aliquot was pipetted into a 10 mL volumetric flask and diluted to volume with acetonitrile.
- Intervals of calibration: Soil log Koc values 1.26 - 4.09; Sewage sludge log Koc values 1.66 - 4.35

REPETITIONS
- Number of determinations: 4
- Injection volume: 2 µL

EVALUATION
The values of log k of individual repetitions are calculated from the individual retention times tR and the average dead time value. The mean of log k is calculated from the individual values of log k. The mean of log Koc of the sample as well as its uncertainty is calculated directly from the mean of log k of the sample and the calibration line.

Log Koc = (logk - b) / a
K = (tR / t0) - 1
Koc =10 to the power of log Koc

Where:
Koc = adsorption coefficient either on soil or sewage sludge (depends on input used)
log Koc = decimal logarithm of the adsorption coefficient (by HPLC)
k = capacity factor
t = retention time of the test compound
t0 = dead time ("retention" time of NO3-)
a = slope of the calibration line
b = intercept of the calibration line
Key result
Type:
log Koc
Value:
> 5
pH:
6.5
Temp.:
25 °C
Matrix:
Soil
Remarks on result:
other: 5.014 ± 1.309
Key result
Type:
log Koc
Value:
> 5
pH:
6.5
Temp.:
25 °C
Matrix:
Sludge
Remarks on result:
other: 6.052 ± 1.834
Details on results (HPLC method):
- Retention times of reference substances used for calibration: Nitrate: 1.24 minutes; Benzamide: 1.834 minutes (used only for soils); Atrazine: 2.291 minutes; Aniline: 2.124 minutes; Linuron: 2.697 minutes; 2,5-Dichloroaniline: 2.721 minutes; Phenyl benzoate: 2.998 minutes; and Phenanthrene: 3.457 minutes
- Details of fitted regression line (log k' vs. log Koc): See tables 1 and 2
- Average retention data for test substance: 5.300 minutes

Table 1: Estimations of parameters of linear regression curve (soil)

Parameter

Estimation

Standard deviation

Lower side of confidence interval

Upper side of confidence interval

Intercept (b)

-0.4974

0.0920

-0.7339

-0.2610

Slope (a)

0.2016

0.0354

0.1107

0.2925

Equation of linear regression curve

logk = a. logKoc + b

logk = 0.2016 logKoc- 0.4974

Statistic parameters

Correlation coefficient

R

0.9309

Coefficient of determination

0.8666

Residual dispersion

s(e)

0.0061

Number of levels

n

7

Number of repetitions

m

4

Student’s t-distribution

t 0.025, n-2

2.571

Table 2: Estimations of parameters of linear regression curve (sludge) 

Parameter

Estimation

Standard deviation

Lower side of confidence interval

Upper side of confidence interval

Intercept (b)

-0.3055

0.0677

-0.4935

-0.1175

Slope (a)

0.1353

0.0241

0.0683

0.2023

Equation of linear regression curve

logk = a. log Koc + b

logk = 0.1353. logKoc - 0.3055

Statistic parameters

Correlation coefficient

R

0.9419

Coefficient of determination

0.8871

Residual dispersion

s(e)

0.0030

Number of levels

n

6

Number of repetitions

m

4

Student’s t-distribution

t 0.025, n-2

2.776

Validity criteria fulfilled:
yes
Conclusions:
Estimations of the adsorption coefficients (Koc) at pH 6.5 and 25 °C were log Koc >5 (5.014 ± 1.309) and log Koc >5 (6.052 ± 1.834) on soil and sewage sludge, respectively.
Executive summary:

The adsorption coefficient of the test substance, Solvent Red 19E, on soil and on sewage sludge was estimated using the HPLC method with reference compounds under GLP conditions.

The test was performed according to the Method C.19, Estimation of the adsorption coefficient (Koc) on soil and sewage sludge using high performance liquid chromatography (HPLC), Council Regulation (EC) No 440/2008, Published in O.J. L 142, 2008 and OECD Test Guideline No. 121, Estimation of the adsorption coefficient (Koc) on soil and on sewage sludge using high performance liquid chromatography (HPLC), Adopted January 22, 2001. 

The test and reference substances were dissolved in methanol. The mobile phase for the column was 55 % ACN + 45 % cutrate buffer (pH 6.5). Estimation of the adsorption coefficient (Koc) on soil and sewage sludge took place at 25 °C

The test substance was more retained on the column than any of the reference standard. The results were obtained by extrapolation of the given calibration curve.

Estimations of the adsorption coefficients (Koc) at pH 6.5 and 25 °C were log Koc >5 (5.014 ± 1.309) and log Koc >5 (6.052 ± 1.834) on soil and sewage sludge, respectively.

Both values of log Koc fall out of the typical range (1.5 to 5.0) in the guidelines, and the results obtained by extrapolation. However this is not considered to be a deviation from the guideline methodology.

Description of key information

Estimations of the adsorption coefficients (Koc) at pH 6.5 and 25 °C were log Koc >5 (5.014 ± 1.309) and log Koc >5 (6.052 ± 1.834) on soil and sewage sludge, respectively.

Key value for chemical safety assessment

Koc at 20 °C:
1 127 197

Additional information

The adsorption coefficient of the test substance, Solvent Red 19E, on soil and on sewage sludge was estimated using the HPLC method with reference compounds under GLP conditions.

The test was performed according to the Method C.19, Estimation of the adsorption coefficient (Koc) on soil and sewage sludge using high performance liquid chromatography (HPLC), Council Regulation (EC) No 440/2008, Published in O.J. L 142, 2008 and OECD Test Guideline No. 121, Estimation of the adsorption coefficient (Koc) on soil and on sewage sludge using high performance liquid chromatography (HPLC), Adopted January 22, 2001. 

The test and reference substances were dissolved in methanol. The mobile phase for the column was 55 % ACN + 45 % cutrate buffer (pH 6.5). Estimation of the adsorption coefficient (Koc) on soil and sewage sludge took place at 25 °C

The test substance was more retained on the column than any of the reference standard. The results were obtained by extrapolation of the given calibration curve.

Estimations of the adsorption coefficients (Koc) at pH 6.5 and 25 °C were log Koc >5 (5.014 ± 1.309) and log Koc >5 (6.052 ± 1.834) on soil and sewage sludge, respectively.

Both values of log Koc fall out of the typical range (1.5 to 5.0) in the guidelines, and the results obtained by extrapolation. However this is not considered to be a deviation from the guideline methodology.

[LogKoc: 6.052]