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Adsorption / desorption

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Endpoint:
adsorption / desorption: screening
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
supporting study
Study period:
2019
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Principles of method if other than guideline:
The Koc of the substance was calculated based on the approach presented in Franco and Trapp (2008), where regressions were developed to predict separately the Koc for the neutral and ionic molecule species of organic electrolytes from their log Kow and pKa values.
GLP compliance:
no
Type of method:
other: calculation according to Franco and Trapp (2008)
Computational methods:
The following equation for bases was applied to the substance:

log Koc = log [Fn * 10^(0.37 * log Pn + 1.70) + FIon * 10^(pKa^0.65 * f^0.14)]

where:

Fn = 1 / (1 + 10^(a * (pH - pKa)))
FIon = 1 - Fn
f = Kow / (Kow + 1)

The following input values were used:
a = -1 for bases
pH = 4.5
Pn = Pow value of the test item as determined by Baker (2010) was 0.074 at pH 12.7 and 20°C
pKa = predicted dissociation constant for the test item as determined by Baler (2010) was 10.25 at 20°C

The resulting calculated log Koc and Koc values were the following:

Log Koc = 1.17 or Koc = 15
Key result
Type:
Koc
Value:
15 L/kg
Conclusions:
The adsorption coefficient of the substance was estimated based on the approach developed by Franco and Trapp (2008). A Koc value of 15 L/kg was calculated based on the substance's pKa value of 10.25.
Endpoint:
adsorption / desorption: screening
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance has a low octanol water partition coefficient and the adsorption potential of this substance is related to this parameter
other:

Description of key information

The adsorption of the substance was calculated based on the approach developed by Franco and Trapp (2008) for the estimation of soil-water partition coefficients for ionisable organic chemicals. In this approach, regressions were developed to predict separately the Koc for the neutral and ionic molecule species of organic electrolytes based on the substance's log Kow and pKa. A Koc value of 15 L/kg was calculated based on a measured pKa value of 10.25.

Key value for chemical safety assessment

Koc at 20 °C:
15

Additional information