Potentiometric determination of trace amounts of amantadine using a modified carbon-paste electrode.

A chemically modified carbon-paste electrode has been described for the sensitive and selective determination of amantadine. Beta-cyclodextrin was used as modifier. The electrode shows a sub-Nernstian response of 51.0 +/- 1.0 mV decade(-1) for amantadine in the concentration range of 6.3 x 10(-10)-7.1 x 10(-7) M at 25 degrees C. The optimum pH value was maintained at 4.5 using a 0.02 M acetate buffer. The limit of detection of the electrode was 6.3 x 10(-10) M of amantadine. The electrode responded very rapidly (<60 s) to changes in the concentration of amantadine, and its lifetime was more than three months. The relative standard deviation of measurements for a 2.0 x 10(-7) M of amantadine was 0.68% (n = 7). The application of a modified carbon-paste electrode to the determination of amantadine in its pharmaceutical preparations showed a relative error of 2%. The recovery of amantadine (2.5 x 10(-8) M) from a blood-serum sample was 94%.