Application of 1-(2-Pyridylazo)-2-naphthol for Separation and Preconcentration of Trace Amounts of Cobalt(II) in Various Samples and Its Determination by Flame Atomic Absorption Spectrometry

Abstract

An atomic absorption spectrometric method for the determination of trace amounts of cobalt(II) after adsorption of its 1-(2-pyridylazo)-2-naphthol (PAN) complex on microcrystalline naphthalene has been developed. This complex is adsorbed on microcrystalline naphthalene in the pH range 3.0-6.0 from a large volumes of aqueous solutions of various alloys and biological samples. After filtration, the solid mass consisting of the cobalt complex and naphthalene was dissolved with 5 mL of dimethyl formamide and the metal was determined by flame atomic absorption spectrometry. Cobalt can alternatively be quantitatively adsorbed on [1-(2-pyridylazo)-2- naphthol]naphthalene adsorbent packed in a column and determined similarly. About 0.35 μg of cobalt can be concentrated in a column from 500 mL of aqueous sample, where its concentration is as low as 0.7 ng/mL. Eight replicate determinations of 1.0 μg/mL of cobalt in final DMF solution gave a mean absorbance of 0.071 with a relative standard deviation of 1.6 %. The sensitivity for 1 % absorption was 62 ng/mL in final DMF solution. The interference of a large number of anions and cations has been studied and the optimized conditions developed were utilized for the trace determination of cobalt in various alloys and biological samples.