Louis A. Coury

Mass Transport in Sonovoltammetry with Evidence of Hydrodynamic Modulation from Ultrasound

Investigations show that continuous ultrasound produces modulated mass transport in sonovoltammetry. At mass-transport-limited potentials, voltammetry in the presence of ultrasound shows near-steady-state behavior with large current output that oscillates about a stable, average value. The current signal consists of a time-independent component and a time-dependent component. As expected for hydrodynamically modulated mass transport, both components are proportional to bulk analyte concentration. We report chronoamperometric determinations of ferrocene during ultrasonic irradiation that have been analyzed using both the time-independent and time-dependent signal components. In both cases, the limit of detection was 4 x 10 -7 mol/L. This paper contains detailed investigations of the time-dependent current signal. The effect of electrolyte viscosity on sonoelectrochemical measurements demonstrates that both current signals arise from convective-mass-transport effects. Third-order, high-frequency cutoff filtering of the chronoamperometric signal shows significant attenuation and smoothing of the time-dependent signal. To explain our results we propose a qualitative model of convective mass transport in sonovoltammetry, where the time-independent current arises primarily from acoustic streaming and the time-dependent component comes from a combination of field-induced fluid motion and cavitational effects.

Preparation of Microarray Electrodes by Sonochemical Ablation of Polymer Films

A new procedure for preparing arrays of microelectrodes based on sonochemical ablation of thin insulating polymer films on electrode surfaces is described. Films are formed through the oxidative electropolymerization of o-phenylenediamine and micron-diameter holes subsequently bumed through films by interfacial acoustic cavitation. Electrodes prepared in this way exhibit steady-state currents in quiescent solution and yield lower detection limits than bare electrodes. This preparation procedure has the potential advantage of being scalable to prepare arrays of arbitrary size

Electrochemical detection of physiological nitric oxide: Materials and methods

Advances in the electroanalytical technology of NO detection make it possible to detect the release of robust concentrations of NO from living systems under pathological or pharmacological conditions. However, technical improvements should enable the construction of research instruments with one or two orders of magnitude improvement in both detection limit and temporal resolution. Such instruments would be capable of revealing physiological NO production and could help quantify the correlations between NO levels and health or disease, ultimately leading to important applications in biomedical research and clinical medicine.