Linear alkylbenzene sulfonate (LAS) is the most important synthetic surfactant in household detergents. Nevertheless, little parent compound-specific information is available about the processes involved in LAS bioconcentration. Here, we employ reversed-phase HPLC to quantify the selected LAS model compounds. The time-dependent tissue distribution and the effect of water hardness on LAS uptake is investigated in order to deepen the understanding of LAS bioconcentration. The concentrations of the selected LAS constituents (C_(10)-2- to C_(13)-2-LAS) in the liver and the internal organs of juvenile rainbow trout increased rapidly demonstrating fast uptake into systemic circulation. The relatively slow increase of LAS concentrations in the less well perfused tissues pointed to internal redistribution being controlled by perfusion. Uptake occurred via the gills rather than the skin. The bioconcentration factors (BCFs) ranged between 1.4 and 372 L kg~(-1) and increased with hydrophobicity in a manner similar to that in fathead minnows. In the latter species the BCFs were higher (6-990 L kg~(-1)) and apparently not related to the fish lipid content. The hydrophobicity dependence of LAS uptake rate constants was affected by water hardness, indicating that hydrophobic and electrostatic interactions played a role in the velocity of LAS uptake. Water hardness was found to reduce electrostatic repulsion to such an extent that hydrophobic interactions became determining for the rate of uptake.
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