In this work, a procedure for preconcentration of cobalt using dispersive liquid–liquid microextraction (DLLME) with the reagent 1-Nitroso 2-naphtol as complexing reagent was developed. At pH 4, Co(II) was complexed with 1-nitroso 2-naphtol and extracted into the fine droplets formed when mixing chloroform (extraction solvent), ethanol (disperser solvent) and the sample solution. After extraction, the phases are separated and cobalt ion was determined in the enriched phase by flame atomic absorption spectrometry (FAAS). Under the optimum conditions, the enrichment factor 57.22 was obtained. The detection limit of the method was 3.76 ng mL-1 and the relative standard deviation (RSD) for eight replicate mrasurements of 0.05 µg mL-1 Co (II) was 2.3 %. The results to the determination of Co(II) in environmental water samples (tap water, well water, mineral water), egg yolk and hair have demonstrated the applicability of the proposed method.
