Carbon fibre, working electrode

Sagar et also used ED to measure plasma terbutaline, but employed a carbon fibre working electrode (14 pm diameter), an Ag/Ag3P04 reference electrode and a stainless steel counter electrode. The applied potential was +1.3 V. Sample prepara-ion was by column switching and HPLC was performed using an ODS-modified silica column with methanol-aq. phosphate buffer (67mmolL pH 5)-aq. SDS (40gL )-DEA (55+45 + 0.5 + 0.02) as eluent (compare with Jarvie et al ). 

Pulses can be direct or reverse on linear potential, or they can increase linearly at a constant potential biopulse is a separate pulse VA system providing DPV and DNPV (according to Brumieve et al.63 ) at MFC (carbon-fibre microelectrode) and two working electrodes in vivo. 

Far from the metal trace analysis, our initial studies with BCFMEs were focused on the determination of folic acid [122], In this case, the main goal was the optimisation of the electrode pretreatment for this analyte. An acidic medium (0.1M perchloric acid) was considered optimum for folic acid determination by differential pulse voltammetry. A linear range between 2.0 x HT8 and 1.0 x 10 6M with a detection limit of 1.0 x 10 8M was obtained. Nevertheless, in this work, the adsorptive properties of the folic acid on mercury were noted and the employment of mercury-coated carbon fibre UMEs for folic acid determination has been targeted as a future goal. 

Dual-electrode detection for CE is much simpler to implement in the microchip format and offers additional sensitivity and selectivity due to the ability to monitor reversible redox reactions as well as help for identifying peaks in complex mixtures. Dual detection with serial gold [90,91] and carbon paste [92], fibre [93] and pyrolysed photoresist [94] working electrodes was reported. 

We developed a submersible electrode assembly, connected to a 50 ft (24 m) long shielded cable (via environmentally-sealed rubber connectors), for the real-time in-situ monitoring of the TNT explosive in natural water [10]. Such sensor assembly consists of the carbon-fibre, silver, and platinum working, reference, and counter electrodes, respectively, and operates in the rapid square-wave voltammetric mode. Such a remote/submersible probe circumvents the need for solution pumping and offer greater simplification and miniaturization. The facile reduction of the nitro moiety allowed convenient and rapid square-wave voltammetric measurements of ppm levels of TNT. Lower (ppb) concentrations have been detected using a... 

A flow injection optical fibre biosensor for choline was also developed55. Choline oxidase (ChOX) was immobilized by physical entrapment in a photo-cross-linkable poly(vinyl alcohol) polymer (PVA-SbQ) after adsorption on weak anion-exchanger beads (DEAE-Sepharose). In this way, the sensing layer was directly created at the surface of the working glassy carbon electrode. The optimization of the reaction conditions and of the physicochemical parameters influencing the FIA biosensor response allows the measurement of choline concentration with a detection limit of 10 pmol. The DEAE-based system also exhibited a good operational stability since 160 repeated measurements of 3 nmol of choline could be performed with a variation coefficient of 4.5%. 

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