Determination of ultra-trace amounts of cobalt in seawater by graphite furnace atomic absorption spectrometry after pre-concentration with Ni/8-quinolinol/1-nitroso-2-naphthol complex

Abstract

A sensitive and accurate method for the determination of ultra-trace amounts of cobalt in seawater is described. Ultra-trace amounts of cobalt were pre-concentrated by co-precipitation with a combination of 8-quinolinol and nickel as a carrier element and 1-nitroso-2-naphtol as an auxiliary complexing agent. The co-precipitates obtained were directly measured by graphite furnace atomic absorption spectrometry using the solid-sampling technique. The co-precipitation conditions for ultra-trace amounts of cobalt with Ni/8-quinolinol/1-nitroso-2-naphtol complex were investigated in detail. It was found that ultra-trace amounts of cobalt are co-precipitated quantitatively with Ni/8-quinolinol/1-nitroso-2-naphtol complex in the pH range of 5.5–8.5. The concentration factor by the co-precipitation reached about 33,000-fold for 1000 ml of the aqueous sample. The proposed method has been successfully applied to the determination of ultra-trace amounts of cobalt in seawater, and the detection limit for cobalt which was defined as the concentration calculated from three times of the standard deviation of the procedural blanks, is 1 ng/l for 1000 ml portions of seawater samples.