Mercury (II) and methyl mercury cations at the Sub-ppb level were adsorbed quantitatively from aqueous solution onto an octadecyl-bonded silica membrane disk modified by 2-[(2-mercaptophyenylimino)methyl] phenol (MPMP). The trapped mercury was then eluted with 3 ml ethanol and Hg2+ ion was directly measured by cold vapor atomic absorption spectrometry, utilizing tin (11) chloride. Total mercury (Hgt) was determined after conversion of MeHg+ into Hg2+ ion by electron beam irradiation. A sample volume of 1500 ml resulted in a preconcentration factor of 500 and the precision for a sampling volume of 500 ml at a concentration of 2.5 mu gl(-1) (n = 7) was 3.1%. The limit of detection of the proposed method is 3.8 ngl(-1). The method was successfully applied to analysis of water samples, and the accuracy was assessed via recovery experiment. (C) 2008 Elsevier B.V. All rights reserved.