A sensitive method for speciation analysis of inorganic mercury (Hg2+) and methyl mercury (MeHg+) has been developed by using high performance liquid chromatography (HPLC) combined with inductively coupled plasma mass spectrometry (ICP-MS) after cloud point extraction. The analytes were complexed with sodium diethyldithiocarbamate (DDTC) and preconcentrated by a non-ionic surfactant Triton X-114. Mercury species were effectively separated by HPLC in less than 6 min. The enhancement factors for 25mL sample solution were 42 and 21, and the limits of detection were 4 and 10ngL(-1) for Hg2+ and MeHg+, respectively. The developed method was successfully applied to the determination of trace amount of mercury species in environmental and biological samples. (C) 2009 Elsevier B.V. All rights reserved.