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Environmental fate & pathways

Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
19 -21 February 2014
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
This study was performed according to OECD Guideline 121 with GLP statement. All validity criteria were fulfilled.
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
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
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes (incl. certificate)
Remarks:
UK GLP Compliance Programme (inspected on 10 July 2012 / signed on 30 November 2012)
Type of method:
HPLC estimation method
Specific details on test material used for the study:
STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Approximately 4 °C in the dark under nitrogen
Radiolabelling:
no
Test temperature:
30 °C
Details on study design: HPLC method:
EQUIPMENT
- Apparatus: High performance liquid chromatograph and a cyanopropyl reverse phase HPLC column containing lipophilic and polar moieties

PREPARATION OF SOLUTIONS:
Preparation of the test item sample solution: Test item (0.1191 g) was diluted to 100 mL with methanol (MeOH) and this solution was diluted by a factor of 10 with MeOH to give a concentration of 119 mg/L.
Preparation of the reference item solutions: Solutions of reference items were prepared in MeOH (see following table 5.4.1/1).

MOBILE PHASES
- Type: methanol: water (55:45 v/v)
- pH of mobile phase: 8.15

DETERMINATION OF DEAD TIME
- The dead time was determined by measuring the retention time of formamide (purity 99.94%, 861 mg/L solution in MeOH:water 55:45 v/v).

REFERENCE SUBSTANCES
- Identity: See Table 5.4.1/1: Reference item solutions

DETERMINATION OF RETENTION TIMES
- The sample, dead time and reference standard solutions were injected in duplicate using the following HPLC parameters:
HPLC System: Agilent Technologies 1100 series, incorporating autosampler
Column: Waters XSelect HSS Cyano 5μm (150 x 4.6 mm id)
Column temperature: 30 ºC
Mobile phase: MeOH:water (55:45 v/v)
pH of mobile phase: 8.15
Flow-rate: 1.0 mL/min
Injection volume: 10 μL
UV detector length: dead time and reference standards: 210 nm; sample: 240 nm

EVALUATION
- A calibration curve was constructed from the retention time data of the dead time and reference standard solutions.
- Calculation of capacity factors k': (tr-t0)/t0
- Determination of the log Koc value:
Log10 Koc = (Log10k' - A) / B
A correlation of log k' versus log Koc of the reference standards was plotted using linear regression.
Note:
k' = capacity factor
tr = retention time (min)
t0 = dead time (min)
Koc = adsorption coefficient
A = intercept of the calibration curve
B = slope of the calibration curve
Key result
Type:
Koc
Value:
719 dimensionless
pH:
8.15
Temp.:
30 °C
Key result
Type:
log Koc
Value:
2.86 dimensionless
pH:
8.15
Temp.:
30 °C
Details on results (HPLC method):
- Retention times of reference substances used for calibration: The retention times of the dead time and the retention times, capacity factors (k') and log10Koc values for the reference standards, determined at a constant HPLC column temperature of 30 °C are shown in tables 5.4.1/2 and 5.4.1/3
- Adsorption coefficient of the sample: The retention times, capacity factor and log10 Koc value determined for the sample at a constant HPLC column temperature of 30 °C, are shown in Table 5.4.1/4.

Table 5.4.1/2: Retention times of the dead time

Dead Time

 

Retention Time (mins)

Mean Retention Time (mins)

Injection 1

Injection 2

Formamide

1.880

1.880

1.880

 

Table 5.4.1/3: Retention times, capacity factors (k') and log10Koc values for the reference standards

Reference Item

Retention Time (mins)

 

Mean Retention Time (mins)

Capacity Factor (k')

 

Log10 k'

 

Log10 Koc

 

Injection 1

Injection 2

Acetanilide

2.726

2.726

2.726

0.450

-0.347

1.25

Phenol 

2.590

2.590

2.590

0.377

-0.423

1.32

Atrazine 

3.984

3.970

3.977

1.12

0.047

1.81

Isoproturon 

4.329

4.320

4.325

1.30

0.114

1.86

Triadimenol

6.166

6.156

6.161

2.28

0.357

2.40

Linuron 

6.307

6.312

6.310

2.36

0.372

2.59

Naphthalene 

5.282

5.301

5.292

1.81

0.259

2.75

Endosulfan-diol 

8.231

8.270

8.251

3.39

0.530

3.02

Fenthion 

10.053

10.107

10.080

4.36

0.640

3.31

α-Endosulfan 

14.966

14.995

14.981

6.97

0.843

4.09

Diclofop-methyl 

16.385

16.385

16.385

7.71

0.887

4.20

Phenanthrene 

10.952

10.933

10.943

4.82

0.683

4.09

 

Table 5.4.1/4: Adsorption coefficient of the sample

Injection

 

Retention Time (mins)

Capacity Factor (k')

 

Log10 k'

 

Log10 Koc

 

Mean Log10 Koc

 

Adsorption Coefficient

 

1

6.395

2.402

0.380

2.85

2.86

719

2

6.419

2.414

0.383

2.86

 

The test item contains no functional groups which would dissociate in the normal environmental pH range (approximately pH 5.5 to pH 7.5); therefore testing was performed without adjusting the pH of the mobile phase.

As the slope of the calibration curve for the reference standards showed good first order correlation and as the retention times between duplicate injections for each solution was consistent, the HPLC method was considered valid for the determination of adsorption coefficient. Based on the chromatographic data, the test item was considered to be stable during the test procedure.

Validity criteria fulfilled:
yes
Conclusions:
The adsorption coefficient (Koc) of the test item has been determined to be 719, log10 Koc 2.86.
Executive summary:

The adsorption coefficient (Koc) for the test substance was determined using an HPLC screening method according to OECD 121 guideline with GLP compliance.

 

The test system utilized a high performance liquid chromatograph and a cyanopropyl reverse phase HPLC column containing lipophilic and polar moieties. The column temperature of 30 °C with a mobile phase consisting of 55 % methanol and 45 % water. A 119 mg/L sample of the test substance was  analyzed using HPLC method. Calibrations were performed using 12 reference items; retention times, capacity factors (k') and log10Koc values for the reference standards were determined at a constant HPLC column temperature of 30 °C. Dead time of the HPLC-system was determined with Formamide. The retention times, capacity factor and log10 Koc value determined for the test substance at a constant HPLC column temperature of 30 °C.

 

Injection

 

Retention Time (mins)

Capacity Factor (k')

 

Log10 k'

 

Log10 Koc

 

Mean Log10 Koc

 

Adsorption Coefficient

 

1

6.395

2.402

0.380

2.85

2.86

719

2

6.419

2.414

0.383

2.86

 

The adsorption coefficient (Koc) of the test item has been determined to be 719, log10 Koc 2.86.

Description of key information

OECD Guideline 121, EU Method C.19, GLP, key study, validity 1:

log Koc = 2.86

Koc = 719

The mobility of the substance is considered as low (according to the criteria developed by P.J. McCall et al., 1981).

Key value for chemical safety assessment

Koc at 20 °C:
719

Additional information

To assess the adsorption potential of the registered substance on soil and on sewage sludge, one key study is available.

This study (WIL, 2015) was performed on the registered substance according to OECD Guideline 121 and EU Method C.19 (HPLC screening method) under GLP conditions. According to this study, the adsorption coefficient log Koc of the registered substance was determined at 2.86. The results indicate that the substance has low mobility (according to P.J. McCall et al., 1981).

1McCall P.J., Laskowski D.A., Swann R.L., and Dishburger H.J., (1981), “Measurement of sorption coefficients of organic chemicals and their use, in environmental fate analysis”, in Test Protocols for Environmental Fate and Movement of Toxicants. Proceedings of AOAC Symposium, AOAC, Washington DC.

Mobility classification scheme:

of Koc

Mobility class

0 - 50

Very high

50 - 150

High

150 - 500

Medium

500 - 2000

Low

2000 - 5000

Slightly

> 5000

Immobile

[LogKoc: 2.86]