Schiff bases, C11-14-tert-alkyl methylene

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

other: HPLC estimation method

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

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))

GLP compliance:

yes

Type of method:

HPLC estimation method

Specific details on test material used for the study:

Substance is closely related to material being registered with similar solublity characteristics.
The substance to be registered, Reaction products of C11-14 tert-alkylamine and formaldehyde is likely to show similar adsorption characteristics in being estimated to adsorb significantly to soil and sediment.

Details on study design: HPLC method:

METHODS
Principle of the test method
HPLC is performed on analytical columns packed with a commercially available solid phase containing lipophilic and polar moieties. For the purposes of this technique a moderately polar stationary phase based on a silica matrix is used:
- O - Si - CH2 - CH2 - CH2 – CN
silica apolar spacer polar moiety
Chemicals injected onto such a column move along it by partitioning between the mobile phase and the stationary phase. The velocity of each component thereby depends on the degree of adsorption to a stationary phase, which exhibits nonpolar as well as polar activity.
This allows for interaction of non-polar and polar parts of a molecule in a similar way as is the case for soil components. This enables the relationship between the retention time on such a column and the adsorption coefficient on the organic part of a soil to be established.
In order to correlate the measured HPLC retention time of a test substance with its adsorption coefficient it is necessary to determine the retention times of a range of reference substances with known adsorption coefficient values. Using the column dead time (from the "retention time" of an inert substance) and the retention data of the reference substances, the k′ values are calculated and a calibration graph of log10KOC versus log10k′ is established. Using the equation of this line the log10k′ result from the test substance is used to estimate its log10KOC value.
Since only the relationship between the retention on the HPLC column and the adsorption coefficient is employed for this evaluation, no quantitative analysis is required and only the determination of the retention time is necessary.
For ionisable substances, where 10% or more of the test substance will be dissociated within the pH range of 5.5 to 7.5, or if no pKa data is available, the log10KOC value of both the ionised and non ionised forms must be estimated in appropriately pH adjusted mobile phases.
There was no pKa value available for Formaldehyde, reaction product with ethylenediamine, therefore, the test substance was assessed at pH <3.5 and >9.5.
HPLC system
An HPLC system comprising the following components was set up;
HPLC pump
Injection valve fitted with 100 μl loop
25 cm × 4.6 mm id column packed with a 5 μm CN phase (Agilent Zorbax SB-CN)
Chromatography data system
Mobile phase
The mobile phase consisted of 55% methanol and 45% pH adjusted deionised water with either formic acid (pH <3.5) or ammonium hydroxide (pH >9.5). The mobile phase was pumped through at a flow rate of 1.5 mL/min. The pH of the pH adjusted deionised water was recorded.
Test procedure
Determination of column dead time (t0)
The solution of sodium nitrate was injected in duplicate to determine t0.
Determination of retention times (tr)
All the reference substances were injected in duplicate and the mean retention times were determined. Each concentration of Formaldehyde, reaction product with ethylenediamine was also injected in duplicate and the mean retention time determined for each concentration.
Blank injections
Blank injections (of pre-acidified/basified mobile phase) were made prior to the determination of t0 and between the determination of t0 and any reference and between any reference substance and test substance injections.
Test temperature
The temperature of the room in which the study was carried out was recorded throughout the study at hourly intervals using an electronic temperature recording instrument.
Test pH
The pKa of Formaldehyde, reaction product with ethylenediamine had not been determined, therefore, the study was conducted in pH adjusted mobile phase; where the deionised water pH was adjusted to pH <3.5 and >9.5. If Formaldehyde, reaction product with ethylenediamine was ionisable the log10 KOC would be determined for both the ionised and non-ionised forms.

Type:

log Koc

Value:

> 5

Remarks on result:

other: pH < 3.5, temperature not availble

Type:

log Koc

Value:

< 1.5

Remarks on result:

other: pH > 9.5, temperature not available

Details on results (HPLC method):

From the experimentally derived k′measurements and the literature KOC values of the reference substances (see table below), the equation of the fitted regression line was determined as log10KOC = a.log10 k′+ b
where, a = slope; b = intercept
These data are displayed graphically in Figures 1 and 2. The coefficient of determination (r2) of these data was calculated as 0.93 for analysis at pH < 3.5 and 0.97 for analysis at pH >9.5, indicating an approximately linear relationship between log10 KOC and log10 k′
The test described has been validated for the quantitative estimation of log10 KOC values in the range 1.5 to 5.0. In those instances where the statistical treatment of the experimental data produces a calculated log10 KOC value outside of this range then the final result is quoted as either <1.5 or >5.0 as appropriate.
The log10 k′for Formaldehyde, reaction product with ethylenediamine could not be calculated at either concentration for analysis at pH <3.5 because the peak did not elute from the column and, therefore, it is outside the range of this method. The estimated log10 KOC for Formaldehyde, reaction product with ethylenediamine is >5.0.
At pH > 9.5 the log10 k′for Formaldehyde, reaction product with ethylenediamine was <1.5 for both 200 and 100 mg/L test concentrations as the test substance eluted before all but one reference substance.
The pH of the deionised water used to prepare the mobile phase was 2.57 for analysis at pH <3.5 and 10.50 for analysis at pH >9.5. The temperature of the room in which the HPLC work was done ranged between 21.3 and 23.4 °C. Although the test temperature exceeded the maximum variation of tolerance of 1.0 °C by 0.1°C, this was deemed to be a minor deviation that had no significant effect on the results.

Substance Test concentration
(mg/L) Soil log10KOC
(literature values)
Acetanilide 10 1.25
Atrazine 10 1.81
Isoproturon 10 1.86
Linuron 10 2.59
Naphthalene 10 2.75
1,2,3-Trichlorobenzene 10 3.16
Fenthion 10 3.31
Phenanthrene 10 4.09
ppDDT 10 5.63

Conclusions:

Log10 KOC values for pH < 3.5 and > 9.5 are > 5 and < 1.5 respectively.
Substance is closely related to material being registered with similar solublity characteristics.
The substance to be registered, Reaction products of C11-14 tert-alkylamine and formaldehyde is likely to show similar adsorption characteristics in being estimated to adsorb significantly to soil and sediment.

Key value for chemical safety assessment

Koc at 20 °C:

31.6

Additional information

Figures used for CSR Log Koc 31.6

Log10 KOC values for pH < 3.5 and > 9.5 are > 5 and < 1.5 respectively.