A polymeric-inorganic composite cation-exchanger, i.e. Nylon-6,6 Sn(IV) phosphate was synthesized via mixing of polymer Nylon-6.6 into the matrices of inorganic precipitate of Sn(IV) phosphate to form composite cation-exchanger. Ion-exchange capacity (IEC), ion-exchange properties, thermal stability and distribution behavior, etc. were also carried out to understand the cation-exchange behavior of the material. The physico-chemical properties of the material were determined using AAS, CHN elemental analysis, FTIR, TGA-DTA, XRD, and SEM studies. On the basis of distribution studies, the material was found to be highly selective for Hg(II), a highly toxic environmental pollutant. Using this electroactive composite material, a new heterogeneous precipitate based selective membrane electrode was fabricated for the determination of Hg(II) ions in solutions. The membrane electrode is mechanically stable, with a quick response time, and can be operated within a wide pH range. The selectivity coefficients for different cations determined by mixed solution method were found to be less than unity. The electrode was also found to be satisfactory in potentiometric titrations. (C) 2009 Elsevier Ltd. All rights reserved.