Applicability of polyaniline (PANI) has been investigated for the preconcentration and speciation of inorganic mercury (Hg²⁺) and methylmercury (CH₃Hg⁺) in various waters (ground, lake and sea waters). Preliminary experiments (batch) with powdered PANI for the quantitative removal of both Hg2+ and CH3Hg+ showed that the retention of Hg²⁺ was almost independent of pH while a pH dependent trend from pH 1 to 12 was seen for CH₃Hg⁺with maximum retention at pH > 5. Time dependence batch studies showed that a contact time of 10 min was sufficient toreach equilibrium. TheKdvalues were found to be ∼8×104 and ∼7×103 for Hg²⁺ and CH₃Hg⁺, respectively.Subsequently column experiments were carried out with PANI and the separation of the species was carried out by selective and sequentialelution with 0.3% HCl for CH₃Hg⁺ and 0.3% HCl–0.02% thiourea for Hg²⁺. This was then followed by further pre-concentration of mercury on agold trap and its determination by CVAAS. The uptake efficiency studies showed that the PANI column was able to accumulate up to 100 mg Hg²⁺/g and 2.5 mg CH3Hg+/g. This method allows both preconcentration and speciation of mercury with preconcentration factors around 120 and 60 for Hg²⁺ and CH₃Hg⁺, respectively. The interfering effects of various foreign substances on the retention of mercury were investigated.