In this work, monomeric 3-([7]helicen-9-yl)thiophene was synthesized and used for the preparation of a polymeric film by electrosynthesis.

In this study we show that nanoparticles of various ferric oxides (hematite, maghemite, amorphous Fe 2 O 3 , b-Fe 2 O 3 and ferrihydrite) incorporated into carbon paste exhibit electro-catalytic properties towards hydrogen peroxide reduction. The modified paste electrode performances were evaluated and compared with those obtained with Prussian Bluemodified carbon paste electrode, which represents an excellent chemical mediator towards the H 2 O 2 redox reaction (as widely described in literature). The best catalytic activity was found for carbon paste modified by amorphous ferric oxide with 2 -4 nm particle size, which was further tested for possible application as hydrogen peroxide sensor. At pH 7, the limit of detection was 2 Â 10 À5 M H 2 O 2 (S/N ¼ 3), the calibration curves were linear upto 8.5 mM H 2 O 2 (R 2 ¼ 0.998), the measurement reproducibility (RSD ¼ 97%, n ¼ 4), the interelectrode reproducibility (RSD ¼ 16%, n electrodes ¼ 5) and < 3 s response time.Keywords: Nanoparticles, Ferric oxide, Iron oxide, Hydrogen peroxide, Sensors, Biosensors, Modified electrodes DOI: 10.1002/elan.200703938 Electrochemical sensing of hydrogen peroxide is an attractive alternative to spectrophotometric [1,2] and chemiluminescence techniques [3,4] for hydrogen peroxide detection. It is also utilized in design of many oxidase-based biosensors [5]. Platinum is the usual material of choice for anodic determination of hydrogen peroxide, due to the relatively rapid electrode kinetics of hydrogen peroxide reduction on platinum oxides [6,7]. Cathodic regime is convenient especially for hydrogen peroxide determinations in biological matrices, since this potential region is usually free from interferences caused mainly by ascorbate and urate, often present in high quantities in biological samples, e.g. body fluids, tissue homogenates, cell lysates etc. [8,9]. In the negative potential region, carbon, in various forms, is one of a few materials which can be successfully used as solid electrode material. Among different carbon materials the carbon nanotubes have been recognized as excellent material for both hydrogen peroxide electroreduction and electrooxidation [10,11]. Recently it has been reported that carbon bamboo structured nanotube paste electrode is more than 20 more sensitive towards hydrogen peroxide compared to the paste which utilize ordinary hollow structure carbon nanotubes [12]. Electrodes made of other carbon forms generally exhibit slow charge transfer kinetics for hydrogen peroxide reduction, therefore high overpotentials are required, in many cases oxygen reduction precedes the onset of hydrogen peroxide reduction wave. To overcome this obstacle, carbon surfaces are modified by various electrocatalytical layers in the case of solid carbon electrodes, or bulk modification is used for carbon paste, screen printed and composite electrodes. While Prussian blue is one of the most frequently used modifier materials for hydrogen peroxide amperometric sensors construction [13] [16]. The aim of this work is to ...

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In electrochemical sensing, a number of voltammetric or amperometric curves are obtained which are subsequently processed, typically by evaluating peak currents and peak potentials or wave heights and half-wave potentials, frequently after background correction. Transformations of voltammetric data can help to extract specific information, e.g., the number of transferred electrons, and can reveal aspects of the studied electrochemical system, e.g., the contribution of adsorption phenomena. In this communication, we introduce a LabView-based software package, ‘eL-Chem Viewer’, which is for the analysis of voltammetric and amperometric data, and enables their post-acquisition processing using semiderivative, semiintegral, derivative, integral and elimination procedures. The software supports the single-click transfer of peak/wave current and potential data to spreadsheet software, a feature that greatly improves productivity when constructing calibration curves, trumpet plots and performing similar tasks. eL-Chem Viewer is freeware and can be downloaded from www.lchem.cz/elchemviewer.htm.

This work describes the method for total antioxidant capacity (TAC) and/or total content of phenolics (TCP) analysis in wines using microdialysis online-coupled with amperometric detection using a carbon microfiber working electrode. The system was tested on 10 selected wine samples, and the results were compared with total reactive antioxidant potential (TRAP), oxygen radical absorbance capacity (ORAC), and chemiluminescent determination of total antioxidant capacity (CL-TAC) methods using Trolox and catechin as standards. Microdialysis online-coupled with amperometric detection gives similar results to the widely used cyclic voltammetry methodology and closely correlates with ORAC and TRAP. The problem of electrode fouling is overcome by the introduction of an electrochemical cleaning step (1−2 min at the potential of 0 V vs Ag/ AgCl). Such a procedure is sufficient to fully regenerate the electrode response for both red and white wine samples as well as catechin/Trolox standards. The appropriate size of microdialysis probes enables easy automation of the electrochemical TAC/ TCP measurement using 96-well microtitration plates.

The paper focuses on the analysis and detection of electroactive compounds using high-performance liquid chromatography (HPLC) combined with electrochemical detection (EC). The fabrication and utilization of electrochemically treated carbon fiber microelectrodes (CFMs) as highly sensitive amperometric detectors in HPLC are described. The applied pretreatment procedure is beneficial for analytical characteristics of the sensor as demonstrated by analysis of the model set of phenolic acids. The combination of CFM with separation power of HPLC technique allows for improved detection limits due to unique electrochemical properties of carbon fibers. The CFM proved to be a promising tool for amperometric detection in liquid chromatography.

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