Modelling electrochemical processes at the three phase junction between electrode–aqueous electrolyte–oil droplet presents a considerable challenge due to the complexity of simultaneous electron transfer between electrode and droplet, ion uptake or expulsion between droplet and aqueous phase, the interaction of redox centers at high concentration, and transport processes accompanying the electrochemical process. For the case of oxidation of para‐tetrahexylphenylenediamine (THPD) microdroplet deposits on basal plane pyrolytic graphite electrodes or random arrrays of microelectrodes (RAM) three models may be envisaged which proceed via A) exchange of ions between droplet and aqueous electrolyte with the electrochemical process commencing at the electrode–oil interface, B) rapid electron transport over the oil–aqueous electrolyte interface and the electrochemical process commencing from the oil–aqueous electrolyte interface inwards, and C) slow electron transport across the oil–aqueous electrolyte interface and the electrochemical process commencing solely from the triple interface. Numerical simulation procedures for these three models, which allow for interaction of redox centers via a regular solution theory approach, are compared with experimental data. A positive interaction parameter, Z=1.4, consistent with a dominant ionic liquid–ionic liquid and neutral oil–neutral oil type interaction is determined from experimental data recorded at sufficiently slow scan rates. The overall mechanism, which governs the voltammetric characteristics at higher scan rates, is shown to be apparently consistent with the triple interface model C). However, the rate of diffusional transport determined by comparison of experimental with simulation data is orders of magnitudes too high. Additional convection processes, possibly of the Marangoni type, appear to be responsible for the fast rate observed for the redox process. The significance of the models presented in the context of microdroplet deposits for other related electrochemical systems is discussed.

The coupling of screen-printing and laser micromachining technology has been used to create a nanovial with "built-in" working and reference electrodes. The volume of the nanovial was calculated to be 7.2 nL using dimensions determined by SEM. The electrochemical nanovial was characterized using the ferri/ferrocyanide redox couple. Cyclic voltammetry and chronoamperometry experiments were performed with electrochemical nanovials utilizing 5% (v/v) glycerin in the solutions and a humidified headspace to control evaporation of the small-volume samples. Chronoamperometry experiments gave results consistent with a diffusion-limited process and revealed a working electrode surface area of 2.6 x 10(4) micron 2. The ultrasmall-volume cells represent a simple, reliable, low-cost approach for the fabrication of complete electrochemical nanovials.

The suitability of ultrasound-assisted anodic stripping voltammetry (sono-ASV) for the detection of total copper content in beer using both mercury thin film and glassy carbon electrodes has been investigated. An immersion horn probe is introduced into a small thermostatted conventional three electrode cell (20 cm 3 ) opposite the working electrode: an ex situ mercury plated Nafion ® -coated mercury film electrode or a bare glassy carbon electrode. Minimal sample pre-treatment is required which consists of acidification of the beer with dilute nitric acid and out-gassing with argon. After the deposition of copper (as the metal or its amalgam) on the electrode in the presence of ultrasound, a square wave scan is employed to get the analytical signal. In the absence of ultrasound, electrode passivation by organic species and lower rates of mass transport prevent the observation of any measurable signals. In situ cavitational cleaning of the electrode by insonation maintains the electrode activity. Total copper content levels in the range of 100 to 300 mg Cu L 21 were determined by sono-ASV using both electrode substrates and showed excellent agreement with values provided by an independent method. This highlights the validity of the sono-ASV method as a useful electroanalytical technique in hostile media.

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A general approach is developed for the numerical simulation of square wave voltammetry (SWV) at uniformly accessible electrodes, based on the backward implicit method. Appropriate transformations of both the spatial coordinate normal to the electrode surface and of the time variable are developed and are shown to lead to efficient and accurate simulations. The method is applied to the modeling of electrochemically reversible processes, and the results predicting the variation of peak height, width at half-height, and the area as a function of square wave frequency and amplitude are shown to be in excellent agreement with the previously derived full analytical theory. Approximate expressions for these quantities are assessed and shown to have limited value. A superior approximation is developed for the case of the peak width at half-height.