Atomic absorption spectrometric determination of trace cadmium after preconcentration with [1-(2-pyridylazo)-2-naphthol]-naphthalene adsorbent or its complex on microcrystalline naphthalene

Cadmium 1-(2-pyridylazo)-2- naphthol complex is quantitatively adsorbed on microcrystalline naphthalene in the pH range 8.0-10.5. It can also be alternatively adsorbed on [1-(2-pyridylazo)-2-naphthol] -naphthalene adsorbent packed in a column at a flow rate of 1-2 mL/min and the metal determined by flame atomic absorption spectrometrically by measuring the absorbance at 228.8 nm against a reagent blank. About 0.05 mug of cadmium can be concentrated in a column from 450 mL of aqueous sample, where its concentration is as low as 0.11 ng/mL. The detection limit is 44 pg/mL for cadmium at the minimum instrumental settings. The linearity is maintained in the concentration range 0.11 ng/mL to 0.4 mug/mL cadmium in aqueous solution or 0.01 to 1.6 mug/mL cadmium in the final DNIF solution with a correlation factor of 0.9995. Eight replicate determinations of 0.3 mug/mL of cadmium in final DMF solution give a mean absorbance of 0.150 with a relative standard deviation of 1.6%. The sensitivity for 1% absorption is 8.8 ng/mL in final DMF solution. The interference of a large number of anions and cations on the determination of cadmium after the preconcentration step have been studied and the optimized conditions developed utilized for its trace determination in various alloys and biological samples. The method may also be used for the determination of cadmium in various environmental samples.