Selective determination of phenols in water by a two-trap tandem extraction system followed by liquid chromatography

The ability of a two-trap tandem system, one containing 300 mg of graphitized carbon black (GCB) and the other filled with 50 mg of Sephadex QAE A-25 strong anion exchanger (SAX), to extract trace amounts of phenols from environmental waters and isolate them from base-neutral species was evaluated. After the water sample had passed through the GCB cartridge, the latter was connected to the SAX cartridge and base-neutral species were removed from the GCB surface by a neutral eluent. Co-eluted very weakly acidic phenols were selectively readsorbed on the SAX surface. Still maintaining the two cartridges in series, an acidified eluent was allowed to flow through the two cartridges to recover the most acidic phenols from the GCB cartridge and the least acidic phenols from the SAX cartridge. After partial removal of the solvent, the final extract was submitted to reversed-phase high-performance liquid chromatography with UV detection. Recoveries of seventeen phenols of environmental concern added to 2 l of drinkgin water at levels between 0.2 and 2 μg/l were higher than 90%. The effect of the presence in water of fulvic acids on the efficiency of the extraction device was assessed. In term of recovery, the two-trap tandem system was compared with other two single extraction cartridges, one containing a chemically bonded siliceous material (C18) and the other SAX material. The limits of detection of the analytes considered were well below 0.1 μg/l.