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Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption
Remarks:
adsorption
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
27 Feb 2012
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Validated QSAR model
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6
Principles of method if other than guideline:
Calculation based on QSAR model in Franco, A. and Trapp, S., Env Tox Chem 27, 10, pp. 1995-2004, 2008. The models are applicable for ionizable organic chemicals or organic electrolytes: acids, bases and amphoters.
GLP compliance:
no
Type of method:
other: calculation
Media:
soil
Type:
Koc
Value:
87 - 108
Remarks on result:
other: from eq. (3)
Type:
log Koc
Value:
1.94 - 2.03
Remarks on result:
other: from eq. (3)
Type:
Koc
Value:
491 - 922
Remarks on result:
other: from eq. (5)
Type:
log Koc
Value:
2.69 - 2.96
Remarks on result:
other: from eq. (5)

The log Koc was calculated at the optimal pH for each regression and additionally at pH values 4, 7 and 9, in order to see the variability at different potential environmental conditions. The Koc values obtained at different pH from both equations are listed in Table 1.

Table 1.

pH

logKoc based on eq. (3)

logKoc based on eq. (5)

6 (optimal for eq. (3))

1.94

-

4.5 (optimal for eq. (5))

-

2.96

4

1.94

2.94

7

1.94

2.96

9

2.03

2.69

AEPD is a primary amine and acts as a base in aqueous solution. At environmental conditions, it will be mainly present in protonated form, i.e. positively charged. Three structurally similar substances can be found in the training set for the model and one in the validation set. The experimental and calculated log Koc values for these substances, listed in Table 2, show that the model performs relatively well for these substances. The difference between experimental and calculated values remains below half a logarithmic unit in most cases and below one unit in all cases. Since, no trend can be observed on which of the equations gives better predictions, it is cautious to use both and select the highest value as worst case for assessment.

Table 2.

 

pKa

logKow neutr.

Exp. log Koc

pH

log Koc calc Eq. 20
pHopt = 6

log Koc calc Eq. 24
pHopt = 4.5

Substance group

CAS

SMILES

Training set

 

 

 

 

 

 

 

 

 

anilin

4,61

0,94

2,58

 

2,44

2,49

Aromatic amine

62-53-3

c1(N)ccccc1

trimethylamin

9,75

0,06

1,99

5,5

2,22

1,89

Aliphatic amine

75-50-3

N(C)(C)C

dimethylamin

10,73

-0,43

2,04

5,5

2,01

1,41

Aliphatic amine

124-40-3

N(C)C

Validation set

 

 

 

 

 

 

 

 

 

n-butylamin

10,69

0,93

1,74

5,5

2,58

2,18

Aliphatic amine

109-73-9

NCCCC

 

Description of key information

logKoc = 2.96 (model by Franco and Trapp, 2008)

Key value for chemical safety assessment

Koc at 20 °C:
922

Additional information

There are no studies available investigating the adsoption/desorption behaviour of 2-amino-2-ethyl-1,3-propanediol (AEPD). The Koc was therefore estimated by calculation.

As primary amine, AEPD is partly present in its positively charged form under environmental pH. The regression used for calculation takes into account the adsorption of the charged and uncharged species. The predicted log Koc was 2.96, indicating low adsorption potential.

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