, Volume 67, Issue 8, pp 1079-1086
Date: 19 Feb 2013

Preparation of a miniaturised iodide ion selective sensor using polypyrrole and pencil lead: effect of double-coating, electropolymerisation time, and current density

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Polypyrrole (PPy) is a conducting polymer which can be used for producing different ion-selective electrodes. An iodide-doped (PPy-iodide) was prepared electrochemically by anodic polymerisation of pyrrole in the presence of an iodide ion in an aqueous solution on the surface of a pencil lead. Polymerisation was investigated under galvanostatic conditions. The effects of electropolymerisation conditions on the characteristics of the potential response of the sensor were examined. Concentrations of pyrrole, iodide ions, and conditioning solution plus current density and the time of electropolymerisation were optimised in relation to the slope and linearity of calibration graphs. This electrode showed a Nernstian behaviour of 61.1 mV per decade for I ion over a wide concentration range from 1.0 × 10−5 M to 1.0 × 10−1 M, with the limit of detection of 9.3 × 10−6 M. The response time of the electrode was from 3–5 s. The selectivity coefficients of the prepared sensors over a wide spectrum of interference anions were also evaluated, revealing that selectivity improves as a result of double-coating with PPy. A similar improvement was observed under lower current density and longer electropolymerisation time. This sensor was applied in the determination of iodide ions using titration potentiometry. This electrode can be used for the determination of iodide in drug preparations.