Synthesis and characterisation of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) Zr(IV) monothiophosphate composite cation exchanger: analytical application as lead ion selective membrane electrode

A Pb2+ ion selective membrane electrode based on poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) Zr(IV) monothiophosphate composite cation exchange material was fabricated using solution casting method. The effect of membrane composition on the proton exchange capacity was investigated by using varying amounts of electroactive material. The membrane with 250mg of electroactive material and 10 mu L of plasticiser exhibited higher proton conductivity. The optimised membrane composition was used for the fabrication of ion selective membrane electrode which exhibited typical Nernstian response towards Pb2+ ions in the concentration range 20.70gL(-1)-20.7 mu gL(-1) (1x10(-1)-1x10(-7)molL(-1)) with a sub-Nernstian slope of 27.429mV per decade change in Pb2+ ion concentration. The response time of the electrode under study for Pb2+ ions was found to be 11s and the electrode can be used for 120days without any considerable divergence in response potential. It can also be successfully used in the pH range from 3.0 to 6.5. It was found selective for Pb2+ ions in the presence of various monovalent, divalent and trivalent interfering metal ions. It was also employed as an indicator electrode in the potentiometric titration of Pb2+ ions using ethylenediaminetetraacetic acid, disodium salt, as a titrant.