Article révisé par les pairs
Résumé : Three types of polymeric electrodes were elaborated using a poly(vinyl chloride) film plasticized with a dioctyl phthalate-nitrobenzene mixture and containing an ion pair of the drug tizanidine. The membrane of the so-called conventional electrode, which includes an internal Ag/AgCl reference, was immobilized on a micropipette tip. A single-layer electrode was prepared by coating a graphite rod with the membrane, while the graphite rod of a two-layer electrode was previously coated with a poly(4,4'-biphenol) film before the sensitive membrane was deposited. These electrodes exhibit a Nernstian response in the concentration range 5 x 10-6-1 x 10-2 M with a slope between 55 and 57 mV per decade. The response is not affected by pH between 3 and 7. The influence of several parameters involved in the construction of these electrodes on their lifetime is discussed, the highest durability being observed for the conventional electrode. Selectivity coefficients against various organic and inorganic cations were evaluated. The conventional electrode was applied to the determination of tizanidine in drug formulations using direct potentiometry.