Preconcentration of trace cadmium from seawater using a dynamically coated column of quaternary ammonium salt on C18-bonded silica gel and determination by graphite-furnace atomic absorption spectrometry

A dynamically coated column of C18-bonded silica gel with methyltricaprylylammonium chloride was used for the selective preconcentration of Cd from water samples under acidic conditions. The complete adsorption of Cd occurred from seawater with no additional reagent, and was found from non-saline waters containing 0.05 - 5 M HCl. The interfering matrix ions were not retained and pass through the column. The sorbed Cd was eluted with 4 mi of 0.1 M HNO3 for a subsequent measurement by graphite-furnace AAS. The technique has been successfully applied to seawater and river-water certified reference materials. The preconcentration process is simple and minimizes the contamination of blanks. The detection limit (3 sigma) is 0.2 ng l(-1) of Cd based on a 75-fold preconcentration.