A clinical assessment of direct electrochemical urate measurements.

The response characteristics of various carbon substrates towards the direct oxidative measurement of urate and other key purine biomarkers have been compared. A novel carbon fibre laminate assembly has been proposed as an alternative substrate for the preparation of disposable sensing strips. The fabrication method is generic and readily transferable to a number of sensor applications.

Anodic stripping voltammetry of sulphide at a nickel film: towards the development of a reagentless sensor.

The determination of sulphide at an electrochemically generated nickel oxide layer at glassy carbon and screen-printed electrodes in acidic media has been examined and appraised. The NiO layer was found to produce a stripping-like signal to sulphide and gave a linear peak current response from 20 to 90 muM. The response was further enhanced by repetitive cycling allowing accumulation of nickel sulphide at the electrode surface such that lower micromolar levels of sulphide (i.

Edge plane sites on highly ordered pyrolytic graphite as templates for making palladium nanowires via electrochemical decoration.

An approach for the fabrication of metal nanowires is presented. Palladium wires with diameters less than 50 nm were produced by electrochemical decoration of step edge sites on the surface of highly ordered pyrolytic graphite via the following three steps. First an electrochemical activation step was used to oxidize the edge plane sites on highly ordered pyrolytic graphite surfaces in 0.

Experimental and theoretical study of the surface-controlled dissolution of cylindrical particles. Application to solubilization of potassium hydrogen carbonate in hot dimethylformamide.

In this paper we present a mathematical model for the surface-controlled dissolution of cylindrical solid particles. This is employed to interpret experimental data published previously for the dissolution of potassium bicarbonate in dimethylformamide at elevated temperatures. Significant kinetic differences in assuming cylindrical rather than spherical shapes are reported with the former representing a closer approximation to the true shape of the particles as revealed by scanning electron microscopy.

Channel flow cell studies on the evaluation of surface pretreatments using phosphoric acid or polymaleic acid for calcite stone protection.

The dissolution kinetics of surface-pretreated and weathered calcite was investigated in dilute acid using a channel flow cell with microdisk detection. Two pretreatments were studied, polymaleic acid and phosphoric acid. Treatment with polymaleic acid was shown to significantly passivate calcite but to a lesser extent than the phosphoric acid and the former coating was found to be less effective for protection of calcite from acid attack.

Voltammetric sizing of inert particles.

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.

Graphite powder and multiwalled carbon nanotubes chemically modified with 4-nitrobenzylamine.

We demonstrate that graphite powder and multiwalled carbon nanotubes (MWCNTs) can be derivatised by 4-nitrobenzylamine (4-NBA) simply by stirring the graphite powder or MWCNTs in a solution of acetonitrile containing 10 mM 4-NBA. We propose that 4-NBA partially intercalates at localised edge-plane or edge-plane-like defect sites and this hypothesis with a range of experimental data provided by electrochemistry in both aqueous and nonaqueous media, electron microscopy and X-ray powder diffraction.

A comparison of different types of gold-carbon composite electrode for detection of arsenic(III).

A study has been conducted using abrasively modified basal and edge-plane graphite, carbon-paste, and carbon-epoxy electrodes to create gold-carbon composite electrodes. Using either nano or micro-sized gold particles their suitability for use in detecting arsenic(III) is assessed. It was found that gold arrays prepared from micron-sized particles gave the best performance for arsenic detection.

Potentiometric differentiation of mono- and macromolecular thiol within human plasma at carbon fiber electrodes.

The potentiometric responses of mono- and macromolecular thiol species derivatized with a naphthoquinone indicator have been assessed at electrode designs based on laminated carbon fiber assemblies. The nature of the response for each type of species was found to depend strongly on the electrode geometry and composition and can be used to discriminate between the different thiol moieties. The efficacy of the electrode systems for the measurement of plasma thiols within normal and diabetic blood samples has been assessed, and a possible mechanism for the differing responses has been proposed.

Abrasively immobilised multiwalled carbon nanotube agglomerates: a novel electrode material approach for the analytical sensing of pH.

We demonstrate for the first time that agglomerates of multiwalled carbon nanotubes (MWCNTs) can be formed in which the binder in the agglomerate is itself a redox-active molecular solid. Two separate agglomerates were formed by dissolving 9,10-phenanthraquinone (PAQ) or 1,2-napthaquinone (NQ) in acetone together with MWCNTs and adding an excess of aqueous solution to cause precipitation of agglomerates, approximately 10 microns in dimension, which consist of bundles of nanotubes running into and throughout the amorphous molecular solid that binds the agglomerate together. The nature of this structure, when immobilised on a substrate electrode and in contact with aqueous electrolyte solutions, gives rise to many three-phase boundaries, electrolyte|agglomerate|conductor, which is advantageous to the solid-state analytical electrochemistry of such a material as it imparts a larger electroactive surface area than other modified carbon electrodes.

Polymer coatings to passivate calcite from acid attack: polyacrylic acid and polyacrylonitrile.

The extent of passivation of calcite toward dissolution by aqueous acids arising from polymeric coatings based on polyacrylic acid or polyacrylonitrile is evaluated using a channel flow cell technique with microdisc electrode detection. In situ passivation with polyacrylic acid leads to a reduction in the reactivity of calcite toward acid attack with a reduction in the rate constant by up to an order of magnitude compared with untreated calcite. Ex situ passivation with polyacrylic acid for 24 h results in good coverage of the calcite by the polymer but it is shown to erode from the surface when exposed to an aqueous acid solution.

Atomic force microscopy studies of the KF (100) surface: formation of water-rich surface phases in moist N,N-dimethylformamide.

A water rich surface phase is observed in the system KF-DMF-H2O by atomic force microscopy; the effects on surface morphology and likely implications for halogen exchange reactions using KF are discussed.

Kinetic isotope effects on the dissolution kinetics of solid salicylic acid in aqueous solution: evidence for solubilisation via a proton dissociation-recombination mechanism.

Quantitative Atomic Force Microscopy measurements made on the dissolving surface of solid salicylic acid in H2O and D2O reveal a kinetic isotope effect (kH/kD = 2.3 +/- 0.6) on the dissolution rate consistent with a transition state in which the proton is dissociated from the dissolving molecule.

Channel Flow Cell Studies of the Inhibiting Action of Gypsum on the Dissolution Kinetics of Calcite: A Laboratory Approach with Implications for Field Monitoring.

The rate of dissolution of surface-treated calcite crystals in aqueous acidic solution has been studied using an adaptation of the channel flow cell method with microdisc electrode detection. Surface treatments of calcite with sulfuric acid lead to the nucleation of gypsum overgrowths, which reduce the rate of dissolution of calcite. Rate constants for untreated calcite and calcite pretreated with sulfuric acid conditions of 0.