Karel Vytřas

Carbon Paste Electrodes in Modern Electroanalysis

Recent trends and advances in the electrochemistry with both unmodified and modified carbon paste electrodes are reviewed (247 refs.). Present day knowledge of their basic physico-chemical properties and characteristics is surveyed, including some specifics important in electrochemical measurements. Special attention is paid to the possibilities of carbon paste-based electrodes in electrochemical investigations and in modern electroanalysis of inorganic ions or molecules, organic substances, biologically important compounds, and pharmaceuticals.

Carbon paste electrodes in the new millennium

In this review (with 500 refs), both electrochemistry and electroanalysis with carbon paste-based electrodes, sensors, and detectors are of interest, when attention is focused on the research activities in the years of new millennium. Concerned are all important aspects of the field, from fundamental investigations with carbon paste as the electrode material, via laboratory examination of the first electrode prototypes, basic and advanced studies of various electrode processes and other phenomena, up to practical applications to the determination of inorganic ions, complexes, and molecules. The latter is presented in a series of extensive tables, offering a nearly complete survey of methods published within the period of 2001–2008. Finally, the latest trends and outstanding achievements are also outlined and future prospects given.

Bismuth-film-plated carbon paste electrodes

Abstract In this preliminary note, carbon paste electrodes (CPEs) plated with a bismuth film are presented. The bismuth film can be generated onto the carbon paste surface either from an external plating solution or in situ; the latter being performed in two ways: (i) as a spike of the Bi 3+ ions to the solution or (ii) via modifying the carbon paste with solid bismuth oxide (5% m/m). As shown on selected examples, bismuth-film-plated CPEs exhibit a good performance in voltammetric stripping analysis of some heavy metals such as Pb, Cd, and Zn.

Recent Advances in Electroanalysis of Organic Compounds at Carbon Paste Electrodes

In this review (with 223 refs), electroanalysis of organic compounds with carbon paste-based electrodes, sensors, and detectors is discussed. The individual methods, covering the period of 2004–2008, are summarized in tables with accompanying commentaries, attention being paid to environmental pollutants, pharmaceutical formulations and drugs, as well as other biologically active organic compounds. Recent achievements and trends are discussed, critically evaluated, and some future prospects are outlined.

Amperometric Determination of Hydrogen Peroxide With a ManganeseDioxide-modified Carbon Paste Electrode Using Flow InjectionAnalysis

A carbon paste electrode bulk modified with MnO 2 was investigated as an amperometric detector for hydrogen peroxide in flow injection analysis (FIA). With an operating potential of +0.46 V versus Ag/AgCl, H 2 O 2 produces catalytic oxidation currents which can be exploited for quantitative determinations. Factors influencing the analytical performance of the electrode, such as paste composition and pH, were studied both for batch voltammetry and for FIA. For the flow system the influence of the injection volume and flow rate were examined. The amperometric signals are linearly proportional to H 2 O 2 concentrations in the range 0.5–350 mg l - 1 , showing a detection limit (three times the signal-to-noise ratio) of 45 µg l - 1 .

Stripping voltammetric determination of mercury(II) at antimony-coated carbon paste electrode.

A new procedure was elaborated to determine mercury(II) using an anodic stripping square-wave voltammetry at the antimony film carbon paste electrode (SbF-CPE). In highly acidic medium of 1M hydrochloric acid, voltammetric measurements can be realized in a wide potential window. Presence of cadmium(II) allows to separate peaks of Hg(II) and Sb(III) and apparently catalyses reoxidation of electrolytically accumulated mercury, thus allowing its determination at ppb levels. Calibration dependence was linear up to 100 ppb Hg with a detection limit of 1.3 ppb. Applicability of the method was tested on the real river water sample.

Voltammetry with carbon paste electrodes containing membrane plasticizers used for PVC-based ion-selective electrodes

Abstract Carbon paste electrodes were prepared by mixing graphite powder with liquids that have been applied as plasticizers for membranes of ion-selective electrodes. In voltammetric measurements, these electrodes exhibited interesting properties such as a wide anodic and cathodic potential range, very low reduction peak of oxygen in the cathodic scan and high extraction and adsorption capabilities. They were shown to be convenient, especially for the selective accumulation of metals in the form of their anionic complexes. Two examples are given. The voltammetric behaviour of gold as its [AuCl4]− complex and of bismuth as the [BiI4]− anion is discussed.

Trace level voltammetric determination of lead and cadmium in sediment pore water by a bismuth-oxychloride particle-multiwalled carbon nanotube composite modified glassy carbon electrode

Two multiwalled carbon nanotubes-based composites modified with bismuth and bismuth-oxychloride particles were synthesized and attached to the glassy carbon electrode substrate. The resultant configurations, Bi/MWCNT-GCE and BiOCl/MWNT-GCE, were then characterized with respect to their physicochemical properties and electroanalytical performance in combination with square-wave anodic stripping voltammetry (SWASV). Further, some key experimental conditions and instrumental parameters were optimized; namely: the supporting electrolyte composition, accumulation potential and time, together with the parameters of the SWV-ramp. The respective method with both electrode configurations has then been examined for the trace level determination of Pb(2+) and Cd(2+) ions and the results compared to those obtained with classical bismuth-film modified GCE. The different intensities of analytical signals obtained at the three electrodes for Pb(2+) and Cd(2+) vs. the saturated calomel reference electrode had indicated that the nature of the modifiers and the choice of the supporting electrolyte influenced significantly the corresponding stripping signals. The most promising procedure involved the BiOCl/MWCNT-GCE and the acetate buffer (pH 4.0) offering limits of determination of 4.0 μg L(-1) Cd(2+) and 1.9 μg L(-1) Pb(2+) when accumulating for 120 s at a potential of -1.20 V vs. ref. The BiOCl/MWCNT electrode was tested for the determination of target ions in the pore water of a selected sediment sample and the results agreed well with those obtained by graphite furnace atomic absorption spectrometry.

Stripping Voltammetric Determination of Iodide with Synergistic Accumulation at a Carbon Paste Electrode

Carbon paste electrodes (CPEs) of various compositions were studied to elucidate the stripping voltammetric behavior of iodide. At an accumulation potential of +0.7 V (vs. Ag/AgCl), the CPE containing tricresyl phosphate as a pasting liquid was able to preconcetrate iodide effectively via ion-pairing reaction followed by oxidation to iodine and its extraction onto pasting liquid. In a supporting electrolyte containing 0.5 M NaCl and 0.1 M HCl, the reduction signal was proportional to iodide concentration from 5 × 10−6 to 5 × 10−7 mol/L with a detection limit of approximately 2.5 × 10−7 mol/L (accumulation for 5 min). Other halides and pseudohalides did not interfere with the determination, except for a high concentration excess of thiocyanate and bromide (100:1). The method was tested on model solutions and was applied to determine total iodine in samples of table salts and mineral water. The results were compared to those obtained by reference methods.

Determination of Hydrogen Peroxide, Glucose and Hypoxanthine using (Bio)Sensors Based on Ruthenium Dioxide‐Modified Screen‐Printed Electrodes

Abstract Screen‐printed electrodes modified with ruthenium dioxide were investigated as amperometric sensors for the determination of hydrogen peroxide using flow injection analysis (FIA). With additions of enzymes (glucose oxidase or xanthine oxidase) immobilized onto the electrode surface via Nafion films, corresponding biosensors for the quantification of glucose or hypoxanthine were developed. Factors influencing their amperometric responses (operational potential, flow rate, pH of the phosphate buffer carrier) were studied in detail. Applications in food analysis were also examined. Supported by the Ministry of Education, Youth, and Sport of the Czech Republic (project MSM0021627502) and from the Grant Agency of the Czech Republic (No. 203/05/2106). Partial support of the CEEPUS program (project PL‐110) is also gratefully acknowledged.