The analytical applications of twin filar electrodes.

摘要

The construction of dip-type probes containing photolithographically-produced, coplanar, interdigitated electrode arrays (twin filar electrodes) and their application in the electro-analysis of species in open solutions are described. Electrodes with filaments 0.0025, 0.0050, and 0.0100 cm wide were fabricated and used to analyze 2-4 mL solutions of ferrocene in acetonitrile and propylene carbonate. Ferrocene concentrations ranged from 1.7 {dollar}times{dollar} 10{dollar}sp{lcub}-6{rcub}{dollar} to 6.3 {dollar}times{dollar} 10{dollar}sp{lcub}-4{rcub}{dollar} M and the steady-state currents observed were between 1.7 {dollar}times{dollar} 10{dollar}sp{lcub}-8{rcub}{dollar} and 2.3 {dollar}times{dollar} 10{dollar}sp{lcub}-6{rcub}{dollar} A. The magnitudes of the steady-state currents at twin filar electrodes during potential-step experiments were shown to be directly proportional to the analyte's concentration and the size of the electrode and inversely proportional to the solvent's viscosity. The collection efficiencies of these electrodes in open solutions were found to be greater than 50% and independent of the size of the electrode. The steady-state currents were also observed to be dependent on the amount of convection present in the solution. Steady-state current measurements were corrected for some of the effects of convection by computing the average of the absolute values of the steady-state currents observed at the separate halves of the twin electrodes.; The transient currents observed at twin filar electrodes during potential-step experiments were quantitated semiempirically using equations derived from a cofacial twin electrode model of potential-step voltammetry. These equations allowed the currents to be described in terms of their behavior at short and long times after the potential step was applied. This semiempirical technique does not depend on knowledge of the nature of mass transport during the transient currents and is, therefore, easier to apply to a wider variety of electrochemical experiments than previous methods of quantitation involving digital simulation.