Determination of cadmium by flame atomic absorption spectrometry after preconcentration on naphthalene–methyltrioctylammonium chloride adsorbent as tetraiodocadmate (II) ions

A sensitive and simple solid-phase preconcentration procedure for enrichment of cadmium prior to analysis by flame atomic absorption spectrometry (FAAS) is described. The method is based on the adsorption of cadmium as CdI42- on naphthalene–methyltrioctylammonium chloride adsorbent, elution by nitric acid and subsequent determination by FAAS. The effect of pH, iodide concentration, sample flow rate, volume of the sample and diverse ions on the recovery of the analyte was investigated and optimum conditions were established. A preconcentration factor of 40 was achieved using the optimum conditions. The calibration graph was linear in the range 1–100 ng ml^-1 cadmium in the initial solution. The detection limit based on the 3Sb criterion was 0.6 ng ml^-1 and the relative standard deviations (RSD) were 3.9 and 1.05% for 5 and 40 ng ml^-1, respectively (n=8). The method was successfully applied to the determination of cadmium added to river, tap and Persian Gulf water samples.