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An advanced potentiometric pH transducer based on processible polyaniline (PCPAn) is reported on. Both glassy carbon and screen-printed carbon electrodes modified with PCPAn by dip-coating exhibited a fully reversible potentiometric response of approximately 90 mV/pH unit over the range from pH 3 to 9. Such a significantly higher potentiometric response of PCPAn-modified electrodes as compared with those of existing devices is explained on the basis of the thermodynamics of polyaniline redox reactions. The PCPAn-based pH transducers exhibit both good operational stability and prolonged shelf life and display a negligible response toward singly charged cations. The new thick-film pH transducer was employed for designing a potentiometric biosensor for urea. In the model solution which mimics blood serum, the urea-sensitive electrode has a detection limit of 10(-5) M urea and a maximum response of approximately 120 mV. The attractive performance characteristics are advantageous over those of existing pH sensors and offer great promise for sensing and biosensing applications.
Karyakin et al. (Wed,) studied this question.