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EC number: 204-694-8
CAS number: 124-28-7
For the determination
of the BCF fish of cationic surfactants classical test methods like OECD
305 are not suitable as the test substance sorbs to negatively charged
surfaces like glass and fish leading to incorrect results. Therefore
modeling is currently the most reliable approach to estimate the
The Arnot & Gobas Model
(2003) for the estimation of the BCF fish takes into adsorption,
distribution, metabolism and excretion (ADME) of a substance in fish.
This model is included in the US EPA Estimation program BCF BAF Version
3.01. The octanol-water partitioning coefficient log Kow is an important
input parameter for this model. The log Kow for the unprotonated
Dimethylalkylamines (DMAs) is calculated with the US EPA KOWWIN Version
1.68 program. For the protonated DMAs the log Kow for the unprotonated
DMAs were calculated by subtraction the empirical factor 3.5 (Fu et al,
2009). This empirical factor is a reasonable one as can be seen when
comparing the difference between the measured Log Kow for the protonated
and unprotonated DMAs (see
IUCLID Chapter 4 Endpoint summary Physical and chemical properties).
Kow for unprotonated and protonated DMAs
With the Log Kow given
in the table above the BCF Fish for the unprotonated and protonated DMAs
were estimated with US EPA BCF BAF Version 3.01 program.
Fish using the US EPA BCF BAF V. 3.01 Program
For all DMAs the
estimated pKa (see IUCLID Chapter 4.21) is 9.78 which means that in the
aquatic environment most of the DMA is protonated.
of DMAs depending on pH
As the chemical
acitivity of a substance in a mixture is additive (Schwarzenbach et al,
Environmental Chemistry, Wiley Interscience, 2003) the BCF fish for a
chain homologue can be at a given pH can be calculated as follows
BCF Fish (pH) = BCF
Fishunprot.* fractionunprot. at pH + BCF
Fishprot.* fractionprot. at pH
In order to calculated
the overall BCF Fish for a DMA substance the BCF Fish (pH) of all
homologues in the substance will be summed up according their relative
fraction in the mixture.
fish for DMA substances for pH 9, 7 and 4
As can be seen from the
table above the overall BCF of the DMAs are low and well below 2000.
As DMAs are readily
biodegraded by microorganisms it can be assumed that metabolism in fish
is reasonable fast as well and can explain why the BCF Fish for DMAs are
The highest estimated
value of 223 can be used for the exposure assessment for secondary
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