Registration Dossier

Diss Factsheets

Environmental fate & pathways

Adsorption / desorption

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
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))
GLP compliance:
yes (incl. QA statement)
Type of method:
HPLC estimation method
Radiolabelling:
no
Details on study design: HPLC method:
Preparation of the test item sample solution
Test item (0.5009 g) was diluted to 50 mL with acetonitrile to give a concentration of 1.00 x 104 mg/L.
Preparation of the dead time solution
The dead time was determined by measuring the retention time of formamide (purity 99.94%, 612 mg/L solution in a matrix of methanol: water (55:45 v/v)).

Solutions of reference items (see following table) were prepared in methanol.

Reference Item Purity (%) Concentration (mg/L)
Acetanilide 99+ 120
Atrazine 99.1 107
Phenol 99.9 143
Isoproturon >98.0 163
Triadimenol 98.0 106
Linuron 99.7 100
Naphthalene 99+ 114
Endosulfan-diol 99.9 160
Fenthion 97.9 152
a-Endosulfan 99.6 101
Phenanthrene ≥99.5 125
Diclofop-methyl 99.1 133
DDT 98.7 144


Determination of retention time
The sample, dead time and reference standard solutions were injected in duplicate using the HPLC system.
As a number of minor components within the test item demonstrated an extremely high affinity for the stationary phase of the column, it was necessary to amend the mobile phase composition to 100% methanol after the retention time of highest calibration standard (DDT) to elute these components. This has no impact on the validity of the adsorption coefficient estimates as all peaks eluted by the amended mobile phase shared a common adsorption coefficient result of greater than that of DDT, log10 Koc >5.63.
Sample No.:
#1
Type:
log Koc
Value:
3.55 dimensionless
pH:
6.7
Temp.:
30 °C
Matrix:
cyanopropyl reverse phase HPLC column containing lipophilic and polar moieties
Remarks on result:
other: Value for the main component representing 72% of Percentage Area Normalization
Sample No.:
#1
Type:
log Koc
Value:
< 1.25 dimensionless
pH:
6.7
Temp.:
30 °C
Matrix:
reverse phase HPLC column containing lipophilic and polar moieties.
Remarks on result:
other: Value for the main component representing 20.43% of Percentage Area Normalization
Details on results (HPLC method):
The test item has an extremely complex composition, with information from the Sponsor indicating 20 discrete species identified by gas chromatography mass spectrometry (GC-MS) analysis. However it should be noted that due to chemical similarities and the limited resolution of the HPLC conditions required by this regulatory method, co-elution of somecomponents was as expected and the reduced number of peaks obtained by HPLC analysis does not conflict with this information. Of the identified species, all but diethyltriamine (1.66%) presented aromatic functional groups and hence the decision to detect the test item by UV absorbance at 270 nm. An initial assessment monitoring 210 nm was also performed and an essentially identical chromatographic profile was obtained; however, a much more significant baseline deviation from the gradient elution method was obtained due to the increased absorbance of methanol at 210 nm. Of the more “universal” detection methods, refractive index cannot be applied to gradient methods and it was therefore feared that higher adsorption coefficient value components may not be eluted by the isocratic conditions indicated by the regulatory method alone. Evaporative light scattering detection (ELSD) is not applicable to volatile components, of which a number, such as simple aromatics, were included in the compositional information.
Of the known test item components, a number contained multiple amine functional groups, with dissociation constants estimated to range from 2.3 to 9.7 (Advanced Chemistry Development Inc., pKa, algorithm version v12.1.0.50374). As such, the relevant components will present a constant cationic form across the whole of the environmentally relevant pH range of 5.5 to 7.5 addressed by the method guidelines. Therefore, only a single determination at an approximately neutral pH (mobile phase pH 6.7) was performed. The method guidelines caution that the estimation method may not be suitable for moderate or strong bases, possibly due to the absence of relevant cationic reference substances with which to generate a more relevant calibration. However, given the composition of the test item, the HPLC estimation method remained the more suitable experimental approach when compared to the alternative batch equilibrium method. In addition, the adsorption coefficient data correlated well with the partition coefficient data generated at pH 12 on the molecular forms of these components under Envigo study number LY74TL. Although ionization to a cationic form increases the water solubility of a substance, typically this does not translate to an increased mobility is soils (and thus a reduced Koc value) due to additional ionic interactions with cation exchange sites.
Validity criteria fulfilled:
yes
Conclusions:
The adsorption coefficient (Koc) of the test item has been evaluated to be in the range less than 17.8 to greater than 4.27 x 105, log10 Koc <1.25 to >5.63. However the chromatographic profile of the test item was dominated by two major peaks. The adsorption koefficient for the largent peak is logKoc=3.55.
Executive summary:

The adsorption coefficient (Koc) of the test item has been evaluated to be in the range less than 17.8 to greater than 4.27 x 105, log10 Koc <1.25 to >5.63. However the chromatographic profile of the test item was dominated by two major peaks. The adsorption koefficient for the main component is logKoc=3.55.

Description of key information

The adsorption coefficient (Koc) of the test item has been evaluated to be in the range less than 17.8 to greater than 4.27 x 105, log10 Koc <1.25 to >5.63. However, the chromatographic profile of the test item was dominated by two major peaks. The adsorption coefficient for the larger peak is logKoc=3.55.

Key value for chemical safety assessment

Koc at 20 °C:
3 550

Additional information

[LogKoc: 3.55]