Voltammetric studies in the absence of added supporting electrolyte are presently dominated by the use of near-steady-state microelectrode techniques and millimolar or lower depolarizer concentrations. However, with this methodology, large departures from conventional migration-diffusion theory have been reported for the [Fe(CN)6](3-/4-) process at both carbon fiber and platinum microdisk electrodes. In contrast, data obtained in the present study reveal that use of the transient cyclic voltammetric technique at glassy carbon, gold, or platinum macrodisk electrodes and K4[Fe(CN)6] or K3[Fe(CN)6] concentrations of 50 mM or greater provides an approximately reversible response in the absence of added electrolyte. It is suggested that the use of very high [Fe(CN)6](3-) and [Fe(CN)6](4-) concentrations overcomes problems associated with a diffuse double layer and that large electrode surface areas and faster potential sweep rates minimize electrode blockage and passivating phenomena that can plague voltammetric studies at microelectrodes. The cyclic voltammetry of the [Fe(CN)6](3-/4-) couple at a range of concentrations at macroelectrodes in the absence of added inert electrolyte is compared with that obtained in the presence of 1 M KCl. The enhanced influences of uncompensated resistance, migration, and natural convection arising from density gradients under transient conditions at macrodisk electrodes also are considered.

The reversible reduction of [S2Mo18O62]4- to [S2Mo18O62]5- and [S2Mo18O62]6- at a glassy carbon macrodisk electrode has been studied by cyclic voltammetry in acetonitrile as a function of the concentration of [(C6H13)4N]4[S2Mo18O62] in the absence and presence of [(C6H13)4N]ClO4 as the added supporting electrolyte. Consideration is given to the influence of scan rate, reference-working electrode distance, [(C6H13)4N]4[S2Mo18O62], and electrolyte concentrations. Experimental data confirm theoretical predictions that cyclic voltammetry at a macrodisk electrode is a viable technique for studies of multiply charged electroactive species without added electrolyte, provided the influence of enhanced complexities associated with effects of increased solution resistance, the mass transport contribution from migration, and convection arising from enhanced density gradients are considered. Enhanced density gradients present in the absence of added supporting electrolyte give rise to a more marked dependence of voltammograms on the angle of the electrode and hence lead to significant distortion of wave shapes at low scan rates. The summation of all these obstacles implies that quantitative evaluation of cyclic voltammograms of multiply charged species requires significantly greater care in the absence than in the presence of added supporting electrolyte.

LAD at an energy of 2.0 J/cm2 (570 mJ) is as effective, with similar adverse events, as an energy of 3.5 J/cm2 (1000 mJ) in facilitating topical anesthesia.

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The synthetic pyrethroid insecticide tetramethrin may be reduced reversibly (E°' = -1.650 V vs Ag/Ag(+)) in acetonitrile at hanging mercury drop electrodes (HMDE) and glassy carbon electrodes. On the voltammetric time scale, the initial electron-transfer process involves the reversible formation of a radical anion. Data obtained from electron paramagnetic resonance spectroscopy indicate that the unpaired electron of the radical is located within the phthalimide system of the molecule. The radical anion may be further reduced at very negative applied potentials with the number of processes being dependent on the nature of the voltammetric technique. The detection limit (3σ) for the determination of tetramethrin in acetonitrile at a glassy carbon electrode, using differential pulse voltammetry, was found to be 2.1 × 10(-6) M. At a HMDE the detection limit is lower, having a value of 9.6 × 10(-7) M. The limit of determination (10σ) at a glassy carbon electrode is 3.5 × 10(-6) M and at a HMDE is 3.0 × 10(-6) M. Tetramethrin was selectively determined in an insecticide formulation, at a glassy carbon electrode using differential pulse voltammetry, at a concentration (w/v) of 0.34 ± 0.02%. The determined concentration is in good agreement with the stated value of 0.350 ± 0.018% (w/v).