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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:
2015-12-02 to 2016-06-22
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))
Version / remarks:
(2001)
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:
The test temperature was measured by a data logger with an interval of 2 minutes. The mean temperature of 22.7 °C was inside the range of 20 - 25 °C ± 1 oc during the course of the study.
Min. Temperature: 22.4 °C
Max. Temperature: 23.0 °C
Mean value: 22.7 °C



Details on study design: HPLC method:
The test was performed temperature controlled, (22.7 oc, mean value) with a mobile phase consisting of 60 % methanol and 40 % HPLC water. A 20 mg/L sample of the test item was analyzed threefold via HPLC on a cyanopropyl (CN-) column with DAD-detection.

Calibrations were performed using eight reference items for soil and seven for sewage sludge with known log Koc values (given by the guidelines). The reference items were measured twice, once before and once after the measurement (double injection of one replicate) of the test item. Dead time of the HPLC-system was determined with sodium nitrate.

EQUIPMENT
- Apparatus: HPLC AGILE NT 1100
- Type: HPLC AGILE NT 1100
- Type, material and dimension of analytical (guard) column: YMC-Pack Cyano, 250 x 4.0 mm
- Detection system: diode array detector (DAD)

MOBILE PHASES
- Type: Methanol : HPLC water (60 : 40)
- Experiments with additives carried out on separate columns: no
- Solutes for dissolving test and reference substances: The test and reference items were dissolved in methanol, diluted to mobile phase ratio and injected into the HPLC-DAD system.

DETERMINATION OF DEAD TIME
- Method: HPLC dead time (to) was determined by threefold injection of a solution of 5 mg/L sodium nitrate

REFERENCE SUBSTANCES
- Identity: sodium nitrate (for determination of dead time), acetanilide, atrazine, monurin, 2,5-dichloroaniline, phenyl benzoate, fenthion, phenantrene, 4,4'-DDT

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 20 µl (5mg/L sodium nitrate)
- Quantity of reference substances: 20 µl


REPETITIONS
- Number of determinations: 2

EVALUATION
- Calculation of capacity factors k': k' = (tr-t0)/t0 (tr: retention time of the test substance, t0: dead time)
- Determination of the log Koc value: Two individual adsorption coefficients for the test item were calculated by experimentally determining its capacity factor k' and inserting k' into the equation log Koc = a ·log k' + b with (a: slope of the calibration graph, b: y-intercept of calibration graph, obtained from the calibration graph). Finally, a mean value was calculated from these individual log Koc values.
Key result
Sample No.:
#1
Type:
log Koc
Value:
4.96 dimensionless
Temp.:
22.7 °C
Matrix:
soil
Key result
Sample No.:
#2
Type:
log Koc
Value:
5.1 dimensionless
Temp.:
22.7 °C
Matrix:
sewage sludge
Details on results (HPLC method):
Two individual log Koc values for soil and for sewage sludge for the test item were derived under consideration of the first and second calibration. Finally a mean value for soil and for sewage sludge was calculated from these individual log Koc values. Based on these data a log Kocof 4.96 for soil was determined for Di(iso)-pentylterephthalate (DPT). Since the mean retention time for the test item was 9.109 min, the log Koc value of 5.1 for sewage sludge was estimated.

- Retention times of reference substances used for calibration: acetanilide 3.2 min , atrazine 3.5 min, monurin 3.6 min, 2,5-dichloroaniline 4.2 min, phenyl benzoate 4.7 min, fenthion 6.5 min, phenantrene 6.6 min, 4,4'-DDT 11.8 min
- Details of fitted regression line (log k' vs. log Koc): The calibration data were obtained from the regression line of the graph log Koc vs. log k'. First calibration of the reference items: Soil: Slope 5.651, Intercept 0.86, r=0.9985. Sewage sludge: Slope 6.123, Intercept 0.7065, r=0.9664
- Average retention data for test substance: Test substance retention time 9.109 min

 Test Item

 log Koc, soil   

 log Koc, sewage sludge   

   1. Calibration  2. Calibration   1. Calibration   2. Calibration
   4.96 ± 0.06   4.96 ± 0.06  5.1 ± 0.3   5.1 ± 0.3
   4.80 to 5.11 (95 % CI)  4.81 to 5.11 (95% CI)  4.3 to 6.0 (95 % CI)  4.3 to 6.0 (95% CI)
 Mean

 4.96   

 5.1   

Koc : Adsorption coefficient according to the guidelines

CI : Confidence Interval

Validity criteria fulfilled:
yes
Conclusions:
The adsorption coefficient log Koc for the test item Di(iso)-pentylterephthalate (D(iso)PT) was determined to be 4.96 for soil and 5.1 for sewage sludge.

Description of key information

The adsorption coefficient log Koc for the test item Di(iso)-pentylterephthalate (D(iso)PT) was determined to be 4.96 for soil and 5.1 for sewage sludge.

Key value for chemical safety assessment

Koc at 20 °C:
125 893

Additional information

The logKOC has been determined in a study conducted according to OECD TG 121 (2001), Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC ) and in GLP compliance. The study resulted in a adsorption coefficient log Koc for the test substance of 4.96 for soil and 5.1 for sewage sludge.

[LogKoc: 5.1]