2,6-dimethyloctan-2-ol

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:

06 December 2016 - 28 February 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

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

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. QA statement)

Type of method:

HPLC estimation method

Radiolabelling:

no

Test temperature:

30 °C

Details on study design: HPLC method:

EQUIPMENT
- Instrument: Agilent Technologies 1200, incorporating workstation and autosampler
- Detector: variable wavelength (VW)
- Column: Xselect Cyano 5 μm (150 x 4.6 mm id)
- Flow: 1.0 mL/min
- Injection volume: 5 µL
- UV detection: 210 nm

MOBILE PHASE
- Type: 55/45 (v/v) methanol/water
- pH: 6.8
- Solutes for dissolving reference substances: reference standards in methanol; dead time solution in 55/45 (v/v) methanol/water

DETERMINATION OF DEAD TIME
- Method: by inert substance which is not retained by the column (formamide)

REFERENCE SUBSTANCES
- Identity: Acetanilide; Phenol; Atrazine; Isoproturon; Triadimenol; Linuron; Naphthalene; Endosulfan-diol; Fenthion; alpha-Endosulfan; Phenanthrene; Diclofop-methyl; DDT.

PREPARATION OF TEST SOLUTIONS
- The test item was used untreated.

REPETITIONS
- Number of determinations: 2 (for reference substances, test solution and blank solution)

EVALUATION
- Calculation of capacity factors k': k'= (tr-t0)/t0 where tr = retention time, t0 = mean column dead time
- Determination of the log Koc value: via linear regression; log k' = 0.3169 x log Koc - 0.762 (r = 0.9276, n = 13)

Key result

Type:

log Koc

Value:

3.58 dimensionless

pH:

6.8

Temp.:

30 °C

Key result

Type:

Koc

Value:

3 760

pH:

6.8

Temp.:

30 °C

Details on results (HPLC method):

The test item was not differentially detected from the mobile phase, due to the absence of chromophores in the test items; even when neat test item was injected, the results weren't any different. It was not possible to determine which peak represented the the test item using UV absorbance (210 nm). High wavelenghts were also tried but without result. Even Evaporative Light Scattering (ELS) was unsuccesful, as the test item was too volatile for this technique.

Therefore, fractions of eluate were collected that covered the major peaks detected when neat test item was injected on the test method. With the aid of gas chromatography with a flame ionization detector (GC-FID), the fractions were analysed and compared to an injection of a solution of test item. This demonstrated that the test item was eluting in a fraction collected over approximately 6 to 7½ minutes and from this it was concluded that the peak at approximately 6½ minutes was the test item. This peak was used to calculate the test result. None of the other fractions collected displayed a significant peak on GC at the retention time seen for the solution of test item. It was considered that the other peaks detected with the test method were impurities that had a significantly greater absorbance differential to the mobile phase. Measurements and results are summarized in the table below.

The test was performed at 30°C (i.e. the temperature of the column), but the log Koc value(s) obtained can be considered to represent the value(s) at an unspecified, probably ambient temperature (ca. 20°C) since no mention is made in the guidelines of the temperature at which the reference substance’s log Koc values were determined. Adsorption coefficients of the test and reference substances are assumed to vary with temperature in the same way.

Validity criteria fulfilled:

yes

Conclusions:

Based on the HPLC estimation method at pH = 6.8 using soil-adsorption reference data, the log Koc for Tetrahydro Myrcenol was determined to be 3.58 (Koc = 3760).

Executive summary:

The adsorption / desorption potential of the substance was tested according to OECD TG 121. The mobile phase was 55/45 (v/v) methanol/water. The column temperature was 30°C, the pH of the mobile phase was 6.8. By means of GC-FID, it was determined that the test item eluted at 6.5 minutes. The log Koc value of the substance was 3.58 (Koc= 3760).

Description of key information

The adsorption / desorption potential of the substance was tested according to OECD TG 121. The mobile phase was 55/45 (v/v) methanol/water. The column temperature was 30°C, the pH of the mobile phase was 6.8. By means of GC-FID, it was determined that the test item eluted at 6.5 minutes. The log Koc value of the substance was 3.58 (Koc= 3760).

Key value for chemical safety assessment

Koc at 20 °C:

3 760

Additional information

[LogKoc: 3.58]