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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:
January 7, 2010 - April 09, 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to same study
Reason / purpose:
reference to other 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))
Principles of method if other than guideline:
Not relevant
GLP compliance:
yes (incl. certificate)
Type of method:
HPLC estimation method
Media:
soil
Radiolabelling:
no
Test temperature:
25 °C
Details on study design: HPLC method:
EQUIPMENT
Commercially available analytical columns packed with a solid phase containing a moderately polar stationary phase with lipophilic and polar moieties (e.g. cyano-propyl bonded phase). The sorption behaviour of the test substnace on soil was investigated using HPLC.

Instrument: Agilent 1200 series Liquid Chromatograph
Column: Hypersil CPS (25 cm x 4.6 mm internal diameter)
Flow rate: 1.0 ml/min
Injection volume: 20 ul
Detector: UV set at 210 nm

MOBILE PHASES
Acetonitrile;water (55:45 v/v)

DETERMINATION OF DEAD TIME
An internal standard (formamide) with no retention on the HPLC column was used to determine the deadtime of the HPLC system.

REFERENCE SUBSTANCES
Please see table 1 for details

DETERMINATION OF RETENTION TIMES
Please see table 1 for details.

REPETITIONS
A solution of benzyl acetate (14.2 mg/l) in HPLC mobile phase, and also containing IDS at the same concentration as in the reference mixture) was prepared and chromatographed in duplicate, bracketed by samples of the reference mixture, using the conditions outlined above.

EVALUATION
The adsorption coefficient is deduced from the capacity factor (k) given by:
tr-to
k = ________
to

where tr is the measured retention time of sample or reference
and to is the retention time of the internal deadline standard.

In order to correlate the measured capacity factor (k) of the test material with its Koc, six reference materials were selected from a list of recommended compunds. These reference compounds were selected to have log10Koc values between 1.3 and 5.6.
Analytical monitoring:
not required
Details on sampling:
Not relevant
Details on matrix:
Not relevant
Details on test conditions:
Not relevant
Computational methods:
A calibration of log10k versus log10Koc was constructed for ther reference standards. The logarithm of the capacity factors for the test substance was then calculated and the log10Koc value was determined by interpolation.
Type:
Koc
Value:
250
Temp.:
25 °C
Type:
log Koc
Value:
2.4
Temp.:
25 °C
Details on results (HPLC method):
Benzyl acetate was determined to have a log10Koc value of 2.4 (equivalent Koc = 250). Please see table 2 for more details.
Adsorption and desorption constants:
Not relevant
Recovery of test material:
Not relevant
Concentration of test substance at end of adsorption equilibration period:
Not relevant
Concentration of test substance at end of desorption equilibration period:
Not relevant
Details on results (Batch equilibrium method):
Not relevant
Statistics:
Not relevant

Table 2: HPLC determination of log10Kocfor benzyl acetate

Sample

Component

tr(mins)

k

Log10k

Log10Koc

Standard Run A (t0= 2.971 mins)

Acetanilide

3.498

0.177

-0.751

1.3

Nitrobenzene

4.253

0.432

-0.365

2.4

Naphthalene

4.890

0.646

-0.190

2.8

2-Methylnaphthalene

5.165

0.738

-0.132

3.9

Anthracene

5.716

0.924

-0.034

4.4

DDT

8.442

1.841

0.265

5.6

Sample A

(t0= 2.971 mins)

Benzyl acetate

4.097

0.379

-0.421

2.4

Sample B

(t0= 2.970 mins)

Benzyl acetate

4.096

0.379

-0.421

2.4

Standard Run B (t0= 2.972 mins)

Acetanilide

3.499

0.177

-0.751

1.3

Nitrobenzene

4.254

0.431

-0.365

2.4

Naphthalene

4.889

0.645

-0.190

2.8

2-Methylnaphthalene

5.164

0.738

-0.132

3.9

Anthracene

5.716

0.923

-0.035

4.4

DDT

8.439

1.840

0.265

5.6

Linear regression (based on mean of standard runs A and B): log10Koc= 4.46 log10k + 4.28

Validity criteria fulfilled:
yes
Conclusions:
Benzyl acetate was determined to have a log10Koc value of 2.4 (equivalent Koc = 250).
Executive summary:

A study was performed according to OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC)). The purpose of the study was to estimate the adsorption coefficient (Koc) of Benzyl acetate by HPLC. Benzyl acetate was determined to have a log10Koc value of 2.4 (equivalent Koc = 250).

Therefore, Benzyl acetate has a medium potential for soil mobility.

Description of key information

A study was performed according to OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC)). The purpose of the study was to estimate the adsorption coefficient (Koc) of Benzyl acetate by HPLC. Benzyl acetate was determined to have a log10Koc value of 2.4 (equivalent Koc = 250).

Therefore, Benzyl acetate has a medium potential for soil mobility.

Key value for chemical safety assessment

Koc at 20 °C:
250

Additional information

[LogKoc: 2.4]