The average size of inert particles is determined using a simple electrochemical procedure. Alumina particles are deposited on an edge-plane graphite electrode, and a cyclic voltammogram is recorded. The scan rate employed varies between 0.2 and 2 V s(-1). At these scan rates the diffusion layer thickness is greater than the size of the alumina particles, minimizing the influence of the particles' height on the observed voltammetry. The average size of the particles is determined via comparison of the experimental voltammograms with simulations.

The voltammetric behaviour of 2,6-dichloro-p-aminophenol (PAP) in aqueous solution at an edge plane pyrolytic graphite electrode was explored and its sensitivity to additions of substituted phenols examined. Proof of concept is shown for the electrochemical adaptation of the Gibbs reaction, where reaction of the oxidised form of PAP with substituted phenols provides an indirect methodology for the analytical detection of these compounds. This indirect protocol provides an attractive alterative to the direct electrochemical oxidation of phenolic compounds, since the latter is plagued by electrode passivation, leading to low sensitivity. It is observed that phenol, 4-phenoxyphenol, methylphenol (para and meta), nitrophenol and most importantly, tetrahydrocannabinol, can be detected voltammetrically. Such a protocol is particularly attractive for roadside testing for cannabis in drug drivers.

The voltammetric responses of chlorine in aqueous acid solutions have been explored using different carbon-based electrodes. Edge-plane pyrolytic graphite has more electrochemical reversibility than glassy carbon, basal-plane pyrolytic graphite, or boron-doped diamond electrodes. A significant reduction in the over-potential is observed on the edge-plane pyrolytic-graphite electrode in contrast with the other carbon-based electrode substrates. These results suggest that edge-plane pyrolytic graphite can be optimally used as the working electrodes in Clark-cell devices for low-potential amperometric gas sensing of Cl2.

The behavior of chloride, bromide and iodide at edge plane pyrolytic graphite electrodes has been explored in aqueous acid solutions. The voltammetric response in each case has been compared with that of basal plane pyrolytic graphite, glassy carbon and boron-doped diamond. The electrochemical oxidation of chloride is found to only occur on boron-doped diamond while the electrochemical reversibility for the oxidation of bromide on edge plane pyrolytic graphite is similar to that seen at glassy carbon whilst being superior to basal plane pyrolytic graphite and borondoped diamond. In the case of iodide oxidation, edge plane and basal plane pyrolytic graphite and glassy carbon display similar electrode kinetics but are all superior to boron-doped diamond. The analytical possibilities were examined using the edge plane pyrolytic graphite electrode for both iodide and bromine where is was found that, based on cyclic voltammetry, detection limits in the order of 10 À6 M are possible.

Enthalpies of transfer ( H3) of the xanthines theophylline and caffeine at very low concentrations (m3) from water to ffl2 molal aqueous alcohols and sucrose were determined calorimetrically. The initial limiting slopes (5 AH3/dm2)m3 in ethanol (m2 = 1, 2, 3) are 0.65 and 0.88 kcal kg mol"2 for theophylline and caffeine, respectively, with the latter value appearing to be the largest reported for a nonelectrolyte In aqueous ethanol. Transfer of theophylline to the homologous series methanol, ethanol, 1-propanol, and 2-propanol (m2 = 1) increases regularly by 0.3 kcal kg mol"2. All results are attributed in part to the energy difference of cavity formation In water and in the more structured aqueous alcohols, respectively, and depend on the size of the transferred nonelectrolyte. The enthalpies of transfer of theophylline and caffeine to 1 m sucrose are each 0.7 kcal/mol lower than in 1 m ethanol, and this constant difference shows that the transfer between two different equlmolal solutions in the limiting region Is independent of these related solutes.