Xylene

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Non-GLP, near guideline study, published in peer reviewed literature, minor restrictions in reporting but otherwise adequate for assessment.

Qualifier:

equivalent or similar to guideline

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:

N/A

GLP compliance:

no

Type of method:

HPLC estimation method

Media:

soil

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material:
Not applicable

Radiolabelling:

no

Test temperature:

20 -25°C

Details on study design: HPLC method:

A Milton Roy liquid chromatograph equipped with a Consta Metric Model III pump, Spectro monitor III 1204A UV detector and a DuPont Instruments 250mm*4.6mm Zorbax cyanopropyl column was used. Sample introduction was via a Rheodyne 7125 injection valve fitted with a 20 µL loop and chromatograms were recorded on a chart recorder set at 10 mm/minute. A wavelength of 255 nm was usually employed for detection. Mobile phase flow rate was 1 mL/minute of volume/volume composition 55 % methanol/45 % water.

Analytical monitoring:

not specified

Details on sampling:

No data reported

Details on matrix:

No data reported

Details on test conditions:

No data reported

Computational methods:

No data reported

Key result

Type:

Koc

Value:

ca. 537 dimensionless

Key result

Type:

log Koc

Value:

ca. 2.73 dimensionless

Details on results (HPLC method):

A calibration curve was generated using reliable Koc values for benzene, toluene, nitrobenzene, naphthalene, 2-methylnaphthalene, phenanthrene and pyrene. These compounds gave the regression equation Log Koc = 2.70 Log K + 2.04 (R2 = 0.99). The Log K value for o-xylene based on the mean of at least two replicates lies within the calibration range.

Adsorption and desorption constants:

No data reported

Recovery of test material:

No data reported

Concentration of test substance at end of adsorption equilibration period:

No data reported

Concentration of test substance at end of desorption equilibration period:

No data reported

Details on results (Batch equilibrium method):

No data reported

Statistics:

No data reported

N/A

Validity criteria fulfilled:

not applicable

Conclusions:

The log Koc of o-xylene estimated using a HPLC method is 2.73.

Executive summary:

This method is equivalent to OECD 121. As this study predates the guideline, there are some details missing from the reporting. However, sufficient detail is provided to allow us to conclude that this study is reliable. A range of compounds for which reliable K and Koc values were available were used to generate a regression equation that allowed the Koc of o-xylene to be estimated. The Log Koc of o-xylene fell within the calibration range. This study is therefore acceptable as a key study for this endpoint.

Description of key information

The log Koc of o-xylene estimated using a HPLC method is 2.73.

Key value for chemical safety assessment

Koc at 20 °C:

537

Additional information

The log Kow of the xylene isomers ranges from 3.12 to 3.2 which suggests the potential to sorb to soil and sediment. A reliable adsorption/desorption study with the Reaction Mass of Ethylbenzene and Xylene as the test substance was not identified. However, a study using the constituent o-xylene that was conducted to a method equivalent to OECD 121 was obtained (Hodson et al 1988). A range of compounds for which reliable K and Koc values were available were used to generate a regression equation that related retention time on the HPLC column to Koc value. This allowed the Koc of o-xylene to be estimated based on the measured K value. The log Koc of o-xylene was 2.73, which fell within the calibration range. Based on similar physico-chemical properties, this value is considered appropriate for read across.