Cobalt determination with FI-FAAS after on-line sorbent preconcentration using 1-nitroso-2-naphthol

The suitability of 1-nitroso-2-naphthol (NN) as a complexing agent for on-line preconcentration of cobalt using C18 microcolumn with FI-FAAS system has been tested. Various parameters affecting the complex formation and its elution were optimized. Reagent solution (2.5×10−3 mol l−1) and aqueous sample solution acidified with 0.1% (v/v) nitric acid were on-line mixed in a reaction coil set at 65±1 °C and flowed through the microcolumn for 30 s. The pH of the mixed solution was adjusted to 3∼4 by adding HNO3 (1 mol l−1) or NaOH (1 mol l−1) in the reagent solution. The adsorbed complexes in the microcolumn were eluted with ethanol (acidified to 1% nitric acid) in 10 s into the nebulizer of FAAS. A good precision (1.6% for 100 μg l−1 Co(II), n=10), high enrichment factor 17.2, with detection limit (3σ) 3.2 μg l−1, and sample throughput (90 h−1) were obtained. The method was applied on the certified reference materials (CRMs) i.e. NBS-362 and NBS-364 (special low alloy steel), for the determination of cobalt and the results were in good agreement with the certified values.