Cobalt Determination by Means of Flow Injection On-line Sorbent Preconcentration-Flame Atomic Absorption Spectrometry with 1-Nitroso-2-naphthol as a Complexing Reagent

The suitability of 1-nitroso-2-naphthol（NN） as a complexing agent for on-line preconcentration of cobalt eluted on the C;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;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 HNO;（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％ HNO;（3.0 mL/min）. A good precision(1.6％ for 100μg/L Co（Ⅱ）, n=10), a high enrichment factor 17.2, with detection limit （3σ） 3.2μg/L, and sample throughput (90 h;) 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.