Simultaneous determination of alkylbenzenesulfonates and dialkyltetralinsulfonates in water by liquid chromatography

A previous method based upon Liquid Chromatography (HPLC) with fluorometric detection for determining linear alkylbenzenesulfonates (LAS) in aqueous environmental samples has been modified for extending it to the monitoring of dialkyltetralinsulfonates (DATS). DATS are reaction byproducts of LAS surfactant synthesis. 10, 100, 200, 1000 ml of respectively untreated sewage, treated one, riverwater and groundwater samples have been extracted by a 0.5-g Graphitized Carbon Black (GCB) cartridge. After sample extraction, co-extracted basic, neutral and weakly acidic compounds have been washed out by a formic acid containing solvent system. DATS and LAS have been then reextracted by passing through the cartridge a basified organic eluant mixture. After solvent removal and residue reconstitution by a suitable solvent system, the subfractionation of the analytes have been achieved by chromatographing them on a C-8 reverse-phase HPLC column. Recovery studies have shown that DATS have been quantitatively extracted by the GCB cartridge. By this procedure, the concentrations in water of DATS entering and leaving two sewage treatment plants in Rome have been monthly monitored over 1 year. With respect to LAS, the higher resistance to biodegradation of DATS has been demonstrated by comparative biodegradation tests. Analysis of a sewage-contaminated groundwater sample has shown that, although DATS are minor components in LAS formulations, the concentration of the former was even higher than that of the latter, with C10 DATS being the most abundant species.