Preconcentration of trace amounts of zinc in seawater using a dynamically coated column of methyltricaprylylammonium chloride on octadecylsilylsilica and determination by graphite-furnace AAS

An octadecylsilylsilica (C-18) column dynamically coated with methyltricaprylylammonium chloride (C-18-Aliquat 336) was examined for the preconcentration of trace amounts of Zn in water samples. Zinc was quantitatively retained on the column from an HCl solution at between 0.5 and 3 mol dm(-3), or seawater acidified with HCl, ranging from 0.5 to 1.0 mol dm(-3). The retention capacity of the C-18-Aliquat 336 for zinc was about 50 mu mol g(-1) from a I mol dm(-3) HCl solution. The Zn retained on the column was completely eluted with 3.5 mi of 0.1 mol dm(-3) nitric acid, and was directly determined by graphite-furnace atomic absorption spectrometry. The precision and accuracy of the present method were demonstrated by analyzing certified reference materials, such as Coastal Seawater (CASS-2) and Riverine Water (SLRS-3). The total procedural blank was 1.9+/-0.4 ng for Zn. The detection limit (3 sigma of the blanks) was 2.4 ng dm(-3) for Zn based on a 125-fold concentration of a 500-ml sample.