Flame atomic absorption spectrometric determination of trace amounts of cobalt in standard alloys and biological samples after preconcentration of its 1,10-phenanthroline complex on tetraphenylborate – microcrystalline naphthalene adsorbent

Abstract

A rapid, simple and sensitive method has been developed for determination of trace amount of cobalt using flame atomic absorption spectrometry. Cobalt is quantitatively retained as 1, 10-phenanthroline-tetraphenylborate ion-associate complex on microcrystalline naphthalene in the <i>p</i>H range 2.6-9.5 from a large volume of its aqueous solutions of various standard alloys and biological samples. After filtration, the solid mass consisting of the cobalt complex and naphthalene is dissolved in 5 mL of dimethylformamide (DMF) and the metal is determined using flame atomic absorption spectrometry by measuring the absorbance at 240.7 nm. Cobalt -1,10-phenanthroline complex can alternatively be quantitatively retained on ammonium tetraphenylborate-naphthalene adsorbent packed in a column at a flow rate of 2 mL/min under the same conditions and determined similarly. In this case, l.0μg of cobalt is concentrated in a column from 400 mL of its aqueous sample, where its concentration is as low as 2.5 ppb. Eight replicate determinations of 4.0 ppm cobalt gives a mean absorbance of 0.120 with a relative standard deviation of 1.8%. The sensitivity for 1% absorption is 147 ppb. The conditions have been optimized and utilized for trace determination of cobalt in various standard samples.