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A new preconcentration method using solid phase extraction (SPE) was developed by immobilizing dithizone (DZ) and 1,4-diphenylsemicarbazide (DPC) on oxidative activated carbon and then using this for the speciation and preconcentration of mercury species (Hg(II) and MeHg(I)) by flow injection cold vapor atomic absorption spectrometry (FI-CVAAS). The SPE experimental conditions were investigated including pH, amount of adsorbent and flow rate. The elution parameters and effect of foreign ions were also elucidated. Under the optimized conditions, the calibration graph was linear in the ranges of 0.015-3.0 μg L-1 of Hg(II), with a detection limit (LOD) of 0.0155 μg L-1 , corresponding to three times the standard deviation (3SD, n = 20). The precision of the method, defined as percentage relative standard deviation (%RSD) for mercury was 1.25-3.79% at concentrations of 0.1-1.0 μg L-1 , for which a preconcentration factor of 20 was obtained for Hg(II). The proposed method was validated by determining the mercury concentration in standard reference materials, and successfully applied to the speciation of mercury in several water and freshwater fish samples.