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

An atomic absorption spectrometric method for the determination of trace am ounts of nickel after adsorption of its 1-(2-pyridylazo)-2-naphthol complex on microcrystalline naphthalene has been developed. This complex is adsorb ed on microcrystalline naphthalene in the pH range 4.5-7.8 from large volum es of aqueous solutions of various alloys and biological and environmental samples containing nickel. After filtration, the solid mass consisting of n ickel complex and naphthalene was dissolved in 5 mL of dimethylformamide, a nd the metal was determined using a flame atomic absorption spectrometer at a wavelength of 232 nm. Alternatively, nickel can be quantitatively adsorb ed on [1-(2-pyridylazo)-2-naphthol]-naphthalene adsorbent packed in a colum n and determined similarly. The calibration curve is linear over the concen tration range 2.0-100 mu g of nickel in 5 mt of the final dimethylformamide solution. Eight replicate determinations of 20 mu g of nickel give a mean absorbance of 0.072 with a relative standard deviation of 1.3%. The sensiti vity for 1% absorption is 0.24 mu g/mL. Various parameters such as the effe ct of pH, the volume of the aqueous phase, and the interference of a large number of metal ions with the determination of nickel have been studied in detail to optimize the conditions for its determination in various standard alloys and biological and environmental samples.