Simultaneous separation-preconcentration and determination of trace amounts of mercury and cadmium in fruits, vegetables and biological samples

Resumo

A method for the simultaneous preconcentration and determination of Hg(II) and Cd(II) at the ng/mL level was studied. This method is based on solid phase extraction using 2-nitroso-1-naphthol-4-sulfonic acid modified natural clinoptilolite zeolite that is selective for mercury and cadmium. The adsorbed complexes could be eluted using dimethylformamid and the concentration of mercury and cadmium were determined by derivative spectrophotometry at appropriate (dA/dλ)s in order to work on the basis of H-point standard addition method. In optimum conditions, detection limit in the original solution is obtained 0.1 ng/mL for mercury and 0.8 ng/mL for cadmium. The preconcentration factor attainable for quantitative recovery (>95%) of Hg(II) and Cd(II) were 95 and 105 for a 1000 mL sample volume, respectively. Five times replicating determination a mixture of mercury and cadmium in 5.0 mL final solution gave a relative standard deviation of 7.8% for Hg(II) and 6.5% for Cd(II). The proposed method is applied to determine mercury and cadmium ions in plant and biological samples successfully.