Preconcentration of trace nickel with the ion pair of disodium 1-nitroso-2-naphthol-3,6-disulfonate and tetradecyldimethylbenzylammonium chloride on microcrystalline naphthalene or by the column method and determination by third derivative spectrophotomet

Nickel is quantitatively retained by disodium 1-nitroso-2-naphthol-3,6-disulfonate (nitroso-R salt) and tetradecyldimethylbenzylammonium chloride (TDBA+Cl−) on microcrystalline naphthalene in the pH range 5.4–12.1 from large volumes of aqueous solutions of various alloys and biological samples. After filtration, the solid mass consisting of the nickel complex and naphthalene was dissolved with 5 ml of dimethylformamide (DMF) and the metal was determined by third derivative spectrophotometry. Nickel complex can alternatively be quantitatively adsorbed on tetradecyldimethylbenzylammonium–naphthalene adsorbent packed in a column and determined similarly. The detection limit is 10 ppb (signal to noise ratio 2) and the calibration curve is linear from 30 to 5.4×103 ppb in dimethylformamide solution with a correlation coefficient of 0.9997 by measuring the distance d3A/dλ3 between λ1 (537 nm) and λ2 (507 nm). Eight replicated determinations of 2.5 μg of nickel in 5 ml of dimethylformamide solution gave a mean intensity (peak-to-peak signal between λ1 and λ2) of 0.339 with a relative standard deviation of ±0.87%. The sensitivity of the method is 0.677 ml/μg found from the slope (d3A/dnm3) of the calibration curve. Various parameters such as the effect of pH, volume of aqueous phase and interference of a number of metal ions on the determination of nickel has been studied in detail to optimize the conditions for nickel determination in various alloys and biological samples.