ON-LINE PRECONCENTRATION SYSTEM USING A MICROCOLUMN PACKED WITH ALIZARIN RED S-MODIFIED ALUMINA FOR ZINC DETERMINATION BY FLAME ATOMIC ABSORPTION SPECTROMETRY

A simple and sensitive on-line flow injection system for determination of zinc with FAAS has been described. The method is based on the separation and preconcentration of zinc on a microcolumn of immobilized Alizarin Red S on alumina. The adsorbed analyte is then eluted with 250 mu L of nitric acid (1 mol L-1) and is transported to flame atomic absorption spectrometer for quantification. The effect of pH, sample and eluent flow rates and presence of various cations and anions on the retention of zinc was investigated. The sorption of zinc was quantitative in the pH range of 5.5-8.5. For a sample volume of 25 mL an enrichment factor of 144 and a detection limit (3S) of 0.2 mu g L-1 was obtained. The precision (RSD, n=7) was 3.0% at the 20 mu g L-1 level. The developed system was successfully applied to the determination of zinc in water samples, hair, urine and saliva.