ROTATING POTENTIOMETRIC ELECTRODE

摘要

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 mu 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. A linear relationship between omega <-1/2>, where omega is the rotating angular frequency, C1/2, the polyion concentration corresponding corresponding to one-half the total maximum DELTA EMF response toward the polyion species was observed. The rotating polycation sensor can also be used as an end-point detector to greatly enhance the analytical resolution and precision for measurement of low concentrations of heparin when such samples are titrated with protamine.