Determination of trace amounts of zinc by flame atomic absorption spectrometry after preconcentration with modified clinoptilolite zeolite.

Natural clinoptilolite was used as a sorbent material for solid-phase extraction and preconcentration of zinc. Clinoptilolite was first saturated with cadmium (II) and then modified with benzyldimethyltetradecylammonium chloride for increasing adsorption of 3-(2-arsenophenylazo)-4,5-dihydroxy-2,7-naphthalene disulfonic acid (neothorin). Zinc was quantitatively retained on the adsorbent by the column method in the pH range of 3.8-4.2 at a flow rate of 1 mL/min. It was eluted from the column with 5.0 mL 2 M nitric acid solution at a flow rate of 1 mL/min and determined by flame atomic absorption spectrometry at 213.9 nm. Zinc could be concentrated from a 0.03 microg/L solution with a preconcentration factor of 170. Relative standard deviation for 8 replicate determinations of 2.5 microg zinc in the final solution was 0.92%. The interference of a large number of anions and cations was studied in detail to optimize the conditions, and the method was successfully applied for determination of zinc in standard and real water samples.