2,2'-azobis[2,4-dimethylvaleronitrile]

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:

21.06.18

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))

Version / remarks:

22.01.2001

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Details on study design: HPLC method:

EQUIPMENT
- Apparatus: HPLC
- Type:
- Type, material and dimension of analytical (guard) column: Reprosil PurCN 125*4.6 mm, with pre-column Phenomenex Securi-tyGuard CN, 4x3 mm
- Detection system: Dionex, DAD-3000

MOBILE PHASES
- Type: isocratic methanol/water 55/45 (% v/v), degassed
- Experiments with additives carried out on separate columns: yes / no
- pH: 7
- Solutes for dissolving test and reference substances: -

DETERMINATION OF DEAD TIME
- Method: by inert substances which are not retained by the column (Sodium nitrate)

REFERENCE SUBSTANCES
- Identity: Phenol, Methylbenzoate, Naphthalene, 1,2,3-Trichlorobenzene, Phenanthrene, 4,4'-DDT

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 10 µg
- Quantity of reference substances: 10 µg
- Intervals of calibration:

REPETITIONS
- Number of determinations: 3 (test item)/ 6 (reference substances)

EVALUATION
- Calculation of capacity factors k': log k’ = 0.1938 * logKOC – 0.0129
- Calculation of retention times:
- Determination of the log Koc value: log KOC = (log k’ + 0.0129) / 0.1938

Key result

Type:

log Koc

Value:

3.108

pH:

7

Temp.:

25 °C

Details on results (HPLC method):

- Retention times of reference substances used for calibration:
- Details of fitted regression line (log k' vs. log Koc): log k’ = 0.1938 * logKOC – 0.0129

- Average retention data for test substance: 4.659 min

Validity criteria fulfilled:

yes

Conclusions:

Variations in the retention times of reference items and test item are very small. Therefore, a stable con-figuration of the HPLC-column can be assumed.
The correlation log k’/log KOC is sufficiently accurate. As calibration gave a coefficient of determination r2 = 0.999.
As peak 2 showed a relative area < 5 %, it was considered as minor peak and only Peak 1 was used for evaluation of the log KOC of the test item.
No observations were made, which might give doubts concerning the validity of the study outcome.

Executive summary:

The study was performed using a HPLC with a cyanopropyl chemical bound resin on a silica base column. Six reference items with different retention times were used to produce a calibration curve, since retention time on cyanopropyl columns and K_OC are correlated. The reference items were chosen on behalf of the retention time of the test item 2,2'-Azobis(2,4-dimethylvaleronitrile) on the column/ on the results of the pre-test.

 

A solvent blank followed by three injections of a solution of the reference items were analysed with HPLC, then three injections of a solution of the test item; and finally three injections of the solution with the reference items, in total ten runs.

For each reference item, the capacity factor k’ was calculated from the retention time of sodium nitrate and the retention time of the respective reference item. A calibration function was set up using the literature values for K_OC of the reference items and the mean capacity factor of the six determinations. In the graph log k’ versus log K_OC, linear regression was performed, giving r² = 0.999.

 

The chromatogram of the test item gave two peaks. With the help of the calibration function log K versus log K_OC, the corresponding log K_OC values were determined as:

 Peak Mean retention time [min] Log K_OC + sd

1* 4.659 3.108 + 0.003

2 5.012 3.312 + 0.004

* (major peak, used for evaluation)

These values are the mean ± standard deviation of three independent determinations

 

Description of key information

The key value is determined in a HPLC screening study. The value indicates a low mobility of the test substance in soil.

Key value for chemical safety assessment

Koc at 20 °C:

1 282