Inorganic anions, potentiometric sensing

PPy is known to exhibit anionic or cationic potentiometric responses depending on the doping ion. PPy films doped with mobile inorganic anions show anionic sensitivity, while PPy films doped with anions of low mobility such as sulfate, large organic anions, or polyanions show cationic sensitivity. This bifunctionality of ionic and redox sensitivity makes PPy apphcable as an all-sohd-state, ion-selective electrode. All-solid-state, potentiometric PPy sensors were developed for potassium and sodium sensing, which showed better response time, selectivity and most importantly long-term stabihty than the coated wire electrode [130]. 

An alternative approach for construction of solid contact electrodes can be also applied by casting the sensitive membrane directly oti the surface of a conductor such as silver or a conductive carbon resin. Thus, two surfactant sensors were prepared using hyamine 1622 or tetradodecylammonium (TDA) as catimiic and DBS as anionic surfactant.The sensing materials were incorporated in a PVC matrix containing o-NPOE as a solvent mediator and applied on a support of a conductive resin without inner reference solution. The responses of these electrodes to DS and DBS as well as the interferences of several common inorganic anions and anionic surfactants were examined. The membranes showed good performance for use as a general potentiometric sensor responsive to anionic surfactants. 

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