Abstract: The suitability of 1-nitroso-2-naphthol(NN) as a complexing agent for on-line preconcen tration of cobalt eluted on the C₁₈ microcolumn by means of the FI-FAAS system was tested.Various parameters affecting the complex formation and its elution were optimized.A 2.3 × 10^-3 mol/L reagent solution and the aqueous sample solution acidified with 0.1 % (volume fraction) nitric acid were on-line mixed (6.4 mL/ min) on a reaction coil set at (65 ±1) ℃ and flowed through the microcolumn for 30 s.The pH of the mixed solution was adjusted to 3-4 with HNO₃(1 mol/L) or NaOH(1 mol/L).The adsorbed complexes in the microcolumn were eluted into the nebulizer of FAAS in 10 s with ethanol acidified with 1 % HNO₃(3.0 mL/min).A good precision(1.6 % for 100 μg/L Co(Ⅱ), n=10), a high enrichment factor 17.2, with detection limit (3σ) 3.2 μg/L, and sample throughput (90 h^-1) were obtained.The method was applied to the certified reference materials(CRMs), NBS-362 and NBS-364, for the determination of cobalt and the results were in good agreement with the certified values.

Key words: Cobalt, FI on-line preconcentration, AAS, 1-Nitroso-2-naphthol