Electrochemical detection of hydrogen peroxide using an edge-plane pyrolytic-graphite electrode (EPPG), a glassy carbon (GC) electrode, and a silver nanoparticle-modified GC electrode is reported. It is shown, in phosphate buffer (0.05 mol L(-1), pH 7.4), that hydrogen peroxide cannot be detected directly on either the EPPG or GC electrodes. However, reduction can be facilitated by modification of the glassy-carbon surface with nanosized silver assemblies. The optimum conditions for modification of the GC electrode with silver nanoparticles were found to be deposition for 1 min at -0.5 V vs. Ag from 5 mmol L(-1) AgNO3/0.1 mol L(-1) TBAP/MeCN, followed by stripping for 2 min at +0.5 V vs. Ag in the same solution. A wave, due to the reduction of hydrogen peroxide on the silver nanoparticles is observed at -0.68 V vs. SCE. The limit of detection for this modified nanosilver electrode was 2.0 x 10(-6) mol L(-1) for hydrogen peroxide in phosphate buffer (0.05 mol L(-1), pH 7.4) with a sensitivity which is five times higher than that observed at a silver macro-electrode. Also observed is a shoulder on the voltammetric wave corresponding to the reduction of oxygen, which is produced by silver-catalysed chemical decomposition of hydrogen peroxide to water and oxygen then oxygen reduction at the surface of the glassy-carbon electrode.

We show that both a random distribution of palladium nanoparticles supported on a BDD electrode or a palladium plated BDD microelectrode array can each provide a sensing platform for the electrocatalytic detection of hydrazine. The palladium nanoparticle modified electrode displays a sensitivity and limit of detection of 60 mA mol(-1) L and 2.6 microM respectively while the array has a sensitivity of 8 mA mol(-1) L with a detection limit of 1.8 microM. The beneficial cost implications of using palladium nano- or micro-particles in sensors compared to a palladium macroelectrode are evident. Interestingly the array of the nanoparticles shows similar sensitivity and limit of detection to the microelectrode array which probably indicates that the random distribution of the former leads to 'clumps' of nanoparticles that effectively act as microelectrodes.

A novel boron-doped diamond (BDD) microelectrode array is characterised with electrochemical and atomic force microscopic techniques. The array consists of 40 micron-diameter sized BDD discs which are separated by 250 microns from their nearest neighbour in a hexagonal arrangement. The conducting discs can be electroplated to produce arrays of copper, silver or gold for analytical purposes in addition to operating as an array of BDD-microelectrodes. Proof-of-concept is shown for four separate examples; a gold plated array for arsenic detection, a copper plated array for nitrate analysis, a silver plated array for hydrogen peroxide monitoring and last, cathodic stripping voltammetry for lead at the bare BDD-array.

A simple portable handheld electrochemical sensor with an integrated sound source for the detection of ultratrace quantities of arsenic using square wave anodic stripping voltammetry is described. The sensor uses low-frequency sound (250 Hz) during the arsenic deposition step to enhance the sensitivity of the arsenic stripping response. It is found that under quiescent (silent) conditions a detection limit of 2.1 x 10(-7) M with a sensitivity of 0.51 M(-1) A is achievable using a 120-s accumulation period, while applying low-frequency sound using a "sonotrode" reduced this detection limit to 3.7 x 10(-9) M with an increased sensitivity of 27.2 M(-1) A. Thus, the low-frequency sonotrode is shown to increase the sensitivity by ca. 50 times while reducing the limit of detection by 2 orders of magnitude. A study of the effect of copper contamination is carried out as well as analysis in real samples; it is found that although as expected copper detrimentally effects the arsenic limit of detection, it does not rise significantly above 10(-8) M levels.

Glassy carbon spherical powder (10-20 microm diameter) modified with cysteine methyl ester is found to be an inexpensive, novel material for the rapid removal of large quantities of toxic heavy metal ions such as Cd(II), Cu(II) and As(III) from aqueous media, with wide ranging potential applications such as third world drinking water filtration or environmental cleanup.