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An ionic liquid (IL) based dispersive liquid-liquid microextraction combined with HPLC hydride generation atomic fluorescence spectrometry method for the preconcentration and determination of mercury species in environmental water samples is described. Four mercury species (MeHg+, EtHg+, PhHg+, and Hg2+) were complexed with dithionate and the neutral chelates were extracted into IL drops using dispersive liquid-liquid microextraction. Variables affecting the formation and extraction of mercury dithizonates were optimized. The optimum conditions found were as follows: IL-type and amount, 0.05 g of 1-octyl-3-methylimidazolium hexafluorophosphate; dispersive solvents type and amount, 500 μL of acetone; pH, 6; extraction time, 2 min; centrifugation time, 12 min; and no sodium chloride addition. Under the optimized conditions, the detection limits of the analytes were 0.031 μg/L for Hg2+, 0.016 μg/L for MeHg+, 0.024 μg/L for EtHg+, and 0.092 μg/L for PhHg+, respectively. The repeatability of the method, expressed as RSD, was between 1.4 and 5.2% ( n = 10), and the average recoveries for spiked test were 96.9% for Hg2+, 90.9% for MeHg+, 90.5% for EtHg+, 92.3% for PhHg+, respectively. The developed method was successfully applied for the speciation of mercury in environmental water samples. [ABSTRACT FROM AUTHOR]