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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 01 July 2015 to 26 July 2016.
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))
Version / remarks:
2008
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))
Version / remarks:
2001
Deviations:
no
GLP compliance:
yes
Type of method:
HPLC estimation method
Media:
soil
Radiolabelling:
no
Details on study design: HPLC method:
CALCULATION OF PKA
-Perrin calculation method (pKalc 5.0, module in Pallas 3.0, CompuDrug International, USA) for the logarithm range of 1 - 14.
-Calculation on each of the three constituents.
-pKa acidic: ≥ 8.1. pKa basic: none.

HPLC CONDITIONS
- Based on the calculated pKa values, the mobile phase was buffered at pH 6.

-Preparation of the buffer pH 6:
-- buffer pH 7, 0.01 M: aqueous solution of 0.01 M potassium di-hydrogenphosphate adjusted to pH 7 using 1 N sodium hydroxide. The buffer contains 0.0009% (w/v) sodium azide.
-- buffer pH 6: buffer pH 7, 0.01 M adjusted to pH 6 using 2 M hydrochloric acid.

- Instrument: Acquity UPLC system (Waters, USA)
- Detector: Acquity UPLC TUV (Waters)
- Column: Acquity UPLC HSS Cyano, 100 mm x 2.1 mm i.d., dp = 1.8 µm (Waters)
- Column temperature: 35°C ± 1°C
- Mobile phase: 55/45(v/v) methanol/buffer pH 6
- Flow: 0.4 mL/min
- Injection volume: 5 μL
- UV detection: 210 nm

UNRETAINED SUBSTANCE, REFERENCE SUBSTANCES AND TEST SUBSTANCE SOLUTIONS
- Unretained substance: formamide
- Reference substances with known log Koc values in the range 1.26 - 5.63: see the table in Results and Discussion.
- Solutions of the unretained substance and of the reference substances were prepared in 55/45 (v/v) methanol/buffer pH 6.

- A 5000 mg/L stock solution of the test substance was prepared in methanol. The stock solution was diluted to obtain an end solution of 55/45 (v/v) methanol/buffer pH 6. Final concentration: 500 mg/L.

INJECTIONS
- The solutions of the unretained substance, the reference substances and the test substance were injected in duplicate.
- Blank solution (55/45 (v/v) methanol/buffer pH 6) was analysed by single injection.

DATA HANDLING
- Dead time (t0)= mean retention time of the unretained substance
- Duplicate capacity factors (k') for each reference substance were calculated from the retention times (tr): k'= (tr-t0)/t0
- Log k’ values of the references substances were plotted against the known log Koc values.
- Linear regression analysis (least squares method) resulted in the following regression line: log k’ = 0.326 log Koc– 0.849 (r=0.98, n=16)
- Capacity factor (k') of the test substance was calculated from its retention time and the dead time.
- Log Koc of the substance was calculated by substituting its mean log k’ in the regression line.
- The value of log Koc obtained from duplicate measurements was within ± 0.25 log units.
Key result
Type:
log Koc
Value:
4.4 dimensionless
Temp.:
20 °C
Remarks on result:
other: Peak area: 7.9%
Type:
log Koc
Value:
3.64 dimensionless
Temp.:
20 °C
Remarks on result:
other: Peak area: 72%
Type:
log Koc
Value:
3.17 dimensionless
Temp.:
20 °C
Remarks on result:
other: Peak area: 2.3%
Type:
log Koc
Value:
2.4 dimensionless
Temp.:
20 °C
Remarks on result:
other: Peak area: 18%
Details on results (HPLC method):
The chromatogram of the test substance solution (500 mg/L) showed four peaks with areas ranging from 2.3% to 72%.

Table: Results Adsorption coefficient (HPLC estimation method)

 

Substance

tr1

[min]

tr2

[min]

mean tr
(n=2)

log Koc

Koc

Area

[%]

 

 

 

 

 

 

 

Formamide (t0)

0.670

0.671

0.671

 

 

 

 

 

 

 

 

 

 

Acetanilide

0.879

0.877

 

1.26

 

 

Monuron

1.079

1.077

 

1.99

 

 

2,5-Dichloroaniline

1.230

1.221

 

2.55

 

 

Naphthalene

1.435

1.430

 

2.75

 

 

Benzoic acid phenylester

1.700

1.692

 

2.87

 

 

Fenthion

2.269

2.246

 

3.31

 

 

Phenanthrene

2.509

2.498

 

4.09

 

 

4,4’-DDT

6.395

6.330

 

5.63

 

 

 

 

 

 

 

 

 

Substance -Peak1

1.242

1.245

1.244

2.40

2.5E02

18

Substance -Peak2

1.691

1.693

1.692

3.17

1.5E03

2.3

Substance -Peak3

2.122

2.123

2.123

3.64

4.3E03

72

Substance -Peak4

3.236

3.237

3.237

4.40

2.5E04

7.9

 

 

 

 

 

 

 

 

Note: log Koc values for the reference substances are mentioned in OECD TG 121 and are based on soil adsorption data.

Conclusions:
A log Koc range of 2.4-4.4 was determined for the substance PEMP product.


Executive summary:

The HPLC estimation method based on soil-adsorption reference data was used for the determination of the adsorption coefficient (Koc) of PEMP product. The mobile phase was 55/45 (v/v) methanol/buffer pH 6 and the wavelength of detection 210 nm. The stationary phase contained cyanopropyl chains chemically bonded to silica. Duplicate measurements. The chromatogram of the test substance solution (500 mg/L) showed four substance peaks with areas ranging from 2.3% to 72%. The log Kow value for the peak with area of 72%, 18%, 7.9% and 2.3% was determined to be 3.6, 2.4 4.4 and 3.2, resp. A log Koc range of 2.4-4.4 was determined for the substance PEMP product. The study was performed in accordance with EC C.9 and OECD 121 and in compliance with GLP.

Description of key information

Log Koc range: 2.4 - 4.4 (EC C.19 and OECD 121: HPLC estimation method).

Key value for chemical safety assessment

Koc at 20 °C:
25 119

Additional information

The chromatogram of the test substance solution (500 mg/L) showed four peaks with areas ranging from 2.3% to 72%.

The maximum value of the log Koc range (from the constituent present at 7.9%) was chosen as the key value for CSA (worst-case approach).

[LogKoc: 4.4]