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A dispersive liquid-liquid microextraction method based on the dispersion of 1,2-dichlorobenzene as an extraction solvent into an aqueous phase in the presence of ethanol as a dispersive solvent for the preconcentration of Co 2+ and Ni 2+ ions is discussed. 1-Nitroso 2-naphtol was used as a chelating agent prior to the extraction and the preconcentrated analyte was determined by flame atomic absorption spectrometry. The effect of various experimental parameters including the extraction and dispersive solvent type and volume, pH, amount of the chelating agent, etc. on the microextraction and complex formation was investigated for finding the optimum conditions. The enhancement factors were about 61.9 and 51.8, the calibration graphs were linear in the range of 10-150 mgL -1 and 10-250 mgL -1 with detection limits of 2.42 mgL -1 and 1.59 mgL -1 , and RSD (n = 5) of 3.08% and 2.17% for cobalt and nickel, respectively. The method was successfully applied to the determination of Co and Ni in water and vitamin B 12 .