Experimental determination of bioconcentration, biotransformation, and elimination of linear alkylbenzene sulfonates in Solea senegalensis

The bioconcentration, biotransformation, and elimination of anionic surfactants, linear alkylbenzene sulfonates (LAS), specifically 2 phi C-10 and 2 phi C-12 LAS, which are pure isomers from two different homologues, have been characterized in Solea senegalensis using an experimental flow-through system with environmental exposure levels. The LAS and their carboxylated metabolites, sulfophenylcarboxylic acids (SPCs), were analyzed by pressurized liquid extraction, followed by solid-phase extraction, liquid chromatography with fluorescence detection, and mass spectrometry. The bioconcentration factors obtained in the steady state were 17.2 +/- 11.2 L/kg for 2 phi C-10 LAS and 386.5 +/- 31.5 L/kg for 2 phi C-12 LAS. A kinetic study also was performed with 2 phi C-12 LAS, and the rate constants of uptake and elimination were K-1 = 177.04 L/kg d and K-2 = 0.92/d, respectively. The formation of the intermediate degradation products was monitored during the 2 phi C-10 LAS experiment, thus allowing, to our knowledge for the first time, the identification and quantification of SPCs from 5 phi C-6 to 9 phi C-10 in marine organisms and in the depuration water as a result of biotransformation by the organisms, diffusive elimination, and excretion. The elimination percentage of the surfactants is both time- and concentration-dependent, and this suggests the existence of a concentration limit for the surfactant in the fish below which the elimination processes are slow. Overall, LAS are not persistent bioaccumulative compounds at environmental exposure levels.