A rotating electrode configuration lowers the detection limits of polyion-sensitive
membrane electrodes. Planar potentiometric polycation and polyanion-sensitive membrane
electrodes were prepared by incorporating tridodecylmethylammonium chloride and
calcium dinonylnaphthalene sulfonate, respectively, into plasticized PVC or polyurethane
membranes, and mounting discs of such films on an electrode body housed in a rotating
disk electrode apparatus of the type used in voltammetry. Due to the unique non-equilibrium
response mechanism of such sensors, rotation of the polyion-sensitive membrane
electrodes at 5000 rpm resulted in an enhancement in the detection limits toward
heparin (polyanion) and protamine (polycation) of at least 1 order of magnitude
(to 0.01 U/ml for heparin; 0.02 g/ml for protamine) over that observed when
the EMF responses of the same electrodes were assessed using a stir-bar to achieve
convective mass transport.
