Determination of cobalt, copper, nickel, lead, and zinc in rocks by solvent extraction and atomic absorption spectrometry

Abstract

A rapid and precise method for the determination of cobalt, copper, nickel, lead, and zinc in silicate rocks by extraction-atomic absorption spectrometry is presented. The sample containing less than 10mg of iron was decomposed with HClO4, HNO3, and HF, and evaporated to dryness, dissolved in diluted HCl. Insoluble residue, if present, was decomposed by heating with phosphoric acid, dissolved and added to the main solution. After the addition of sodium tartrate to the solution, the pH was adjusted to about 8, then 1-nitroso-2-naphthol solution was added. The pH was raised to 1010.5, sodium diethyldithiocarbamate solution was then added, and the solution was shaken with butyl acetate. Metals in the organic phase were determined by atomic absorption spectrometry using air-acetylene flame. The relative standard deviation in the determination of 1μg to 20μg of metals is 2% to 14%. The detection limits were 0.5ppm for cobalt, copper, nickel, and zinc, and 2ppm for lead. The method is satisfactorily applied to a variety of reference rock samples.