Toxicity measurements in concentrated water samples - Rivm

Environmental parameters
As discussed, several parameters have a bearing on extraction, which are summarized in Table 3-2. So
far, no experimental concessions have been made to reduce the influence of environmental parameters
during extraction.
Temperature
Adsorption of hydrophobic substances increases as the temperature rises. Adsorption of
hydrophilic substances such as nonionogenic surfactants decreases. Therefore we chose to
carry out the extractions at ambient temperature.
Light
Surface water samples usually contain different forms of life, e.g. algae. In light, algae
continue primary production, resulting in an increase in pH, which in turn can change the
effectiveness of the adsorption of chemicals. Photodegradation of components may also
occur. For this reason, extractions were carried out under reduced light conditions.
In addition to the parameters mentioned in Table 3-2, it was also checked if the concentration of
organic solvents in the water could disturb the extraction. It was found that only above a solvent
concentration of 20 % (!) extraction efficiency decreased. Such values are far above values found in
surface waters.
Table 3-2. Summary of the influence of some parameters on the extraction efficiency. For more detailed
information see Struijs and Van Buren (1995).
extraction
Parameter Substance group
efficiency when
parameter value
increases
pH
Ionic strength, NaCl
Temperature
Water solubility
acids -
bases +
nitrosamines +
nonionogenic detergents +
hydrophobic +
hydrophilic -
extremely hydrophobic -
weakly hydrophobic +
weakly hydrophilic +
extremely hydrophilic -
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